The 2022 Tropical Season: What are Tropical Systems?

In the Southeast, almost nothing gets more press than the Atlantic Tropical Season, including the outlooks, real-time events, and post-storm analyses. If you live in another part of the United States or the world, you may not be as directly affected as the Southeast is, but you might be surprised at how far and wide tropical moisture is spread, either directly by tropical storms and hurricanes or by the remnant moisture which can be carried with the winds for long distances away from their original sources. This week I will describe what tropical systems are and what they mean for gardeners. In my next post, I will review the current season, including any impacts that have occurred. Don’t let the early quiet conditions fool you—about 90% of Atlantic tropical activity occurs from mid-August through mid-October.

Hurricane lily (Lycoris radiata var. radiate). Source: Tonbu Mizo, Commons Wikimedia. For why they are called “hurricane lilies”, visit https://gardeningsolutions.ifas.ufl.edu/plants/ornamentals/hurricane-lily.html.

What is a tropical system?

I am using “tropical system” as a term that encompasses the life cycle of a tropical disturbance from birth to death. That may include formation by a tropical wave coming off Africa, developing in the Gulf of Mexico, or growing in the Eastern Pacific Ocean, then a tropical storm, a hurricane (maybe even a major one), and eventually a slow death as a tropical depression or extra-tropical low that has lost its tropical characteristics.

The map below shows historical tracks for all known storms across the globe. Note that in some regions they are called hurricanes and others, typhoons, but both are tropical cyclones, the generic name for rotating, organized systems of thunderstorms that originate over tropical waters and have closed, low-level circulations. The pattern of tracks shows some interesting information about tropical systems. For example, why are there almost no tracks in the eastern part of the South Pacific Ocean or in the southern Atlantic? Why do many of the tracks show a curve as the storm moves from east to west? Why are there more storms in the Northern Hemisphere (NH) than in the Southern (SH)? Why are there almost no tracks along the equator?

A picture containing nature

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Historical tropical storm tracks. Color coding indicates tropical depressions (green), tropical storms (yellow), hurricanes (red), and post-tropical storms (gray).

What ingredients are needed for tropical systems to develop?

Tropical systems form from areas of low pressure that develop rotation (counterclockwise in the NH and clockwise in the SH) as the storms’ pressure decreases. For the storm to strengthen, it needs favorable conditions to cause rising air in the center, which drops the pressure at the surface. One ingredient is ocean surface temperature of 80 F or higher (27 C)—that explains why almost no storms develop in the southeastern Pacific or southern Atlantic, since both are far too cold. Tropical storms and hurricanes are considered to be “warm core” systems with the air in the center of the storm staying warm all the way to the top of the circulation. The peak season of storms in the Atlantic is related to the cycle of ocean temperatures, with the highest likelihood of storms in the period from mid-August to mid-October. As ocean temperatures warm, this could mean a shift in hurricane season in the future.

For spin to develop, you need a force called the Coriolis force that affects the atmosphere due to the earth’s rotation around its axis. The Coriolis force is zero at the equator so any areas of low pressure that form in that area can’t develop the necessary spin to form storms. Another ingredient is light winds higher up in the atmosphere. This allows the vertical structure of the storm to develop a strong circulation that ultimately becomes a hurricane. This becomes important when we talk about the impacts of El Nino and La Nina on predictions of tropical seasons, since El Nino years have much stronger jet streams in tropical regions than La Nina or neutral conditions do.

The curvature of the tracks is due to the mid-level winds in the atmosphere that steer the storms as they go through their life cycles. The counterclockwise flow of air around ridges of high pressure systems push the storms along their edges. This often results in a C-shaped pattern as the storm travels around the western edge of the oceanic high pressure, although the position and strength of the high pressure will help determine the path each storm takes and when or if it recurves to the northeast.

Depiction of a hurricane life cycle, from a tropical disturbance (easterly wave off the West coast of Africa) to a fully formed hurricane. Image credit: NOAA/NHC.

Impacts of tropical systems

Some impacts of tropical systems are only found near the center of the circulation, but others can be found hundreds of miles away, so even if you are not in the main area that tropical storms affect, you are not without risk. These storms are not small whirls like tornadoes, but are much bigger and can take hours to cross a location near the center. If you are close to the storm’s center, especially if you are on the right side of the storm’s path, you are likely to experience strong winds, heavy rain, and, if you are near the coast, the chance of a storm surge coming inland from the ocean. Farther away, you can experience strong squalls that include small tornadoes, heavy rains, and gusty winds. These effects are made worse if you live in mountainous areas where lifted air can cause rapid flooding conditions. Some of the worst floods in U. S. history are from former hurricanes that traveled over mountains and dropped incredible amounts of rain, such as Agnes, which caused the death of 122 people mostly in Pennsylvania, almost exactly 50 years ago.

Even after a storm weakens to a depression or transforms into an extra-tropical storm, the blob of moisture within the remains of the storm can be transported by the atmospheric circulation a long ways. There have been records of typhoons in the Western Pacific Ocean whose watery remains crossed the ocean and brought heavy rain to the West Coast. Occasionally some will enter the central United States and drop flooding rain there, too, such as the remains of Tropical Storm Erin in 2007.

Hurricane Dennis batters palm trees and floods parts of Naval Air Station (NAS) Key West’s Truman Annex, U.S. Navy photo by Jim Brooks

What gardeners (and everyone else) should know

Preparing a garden for a hurricane is no different than preparing for other types of extreme weather. Survey your property before the season to make sure that no objects that could blow around in high winds damaged are present. If a storm is coming, make sure that your yard is free of garden gnomes, rakes, damaged tree limbs, or other loose objects that could become airborne. Make sure your roofs and gutters can shed heavy rain and have a place on your property to contain rainwater safely. Have supplies of batteries, non-perishable food, and water for people and pets. Put together a plan to recover later by making inventories of your property, including outdoor equipment that you store online. And make a family plan for how to evacuate if you live in an area of flooding and how to contact each other later if you get separated. Cell phones often do not work after strong wind events, so you can’t count on them to bring your family back together quickly after a storm.

What’s next?

I expect to see the Atlantic tropical season start to pick up by mid-August, when the African dust that is currently inhibiting storm formation clears and the ocean temperatures get even warmer. In fact, today’s 5-day outlook map shows an area of possible development in the eastern Atlantic (as of 8-6-2022). This is expected to be another active season, and even though we’ve only had three named storms so far, we will likely see many more storms before the end of November, when the official season ends. In my next blog, we will look at the season so far in more detail.

*Summertime, and the livin’ is easy…

If you listen closely you can hear the beasties in your garden just a-singin’ that tune. And who can blame them? Warm temperatures and lush green gardens? They enjoy them as much as we do. But sometimes they can be enjoying our landscape a little too much. So now what do you do?
Visit the garden chemicals section at your local big box store?
Reach for your favorite “natural” or DIY concoction?
Ask your neighbor?

Hmmm, maybe not.

What is the best way to deal with the problem?
Three letters answer that question.

IPM.

Scoutcat logo courtesy of C. Ware, copyright 2000


What is IPM? Integrated Pest Management (IPM) is the management approach you should use to solve pest problems. It can manage all sorts of pests with minimal risks to people, pets, and the environment. IPM’s emphasis is on the management of problems rather than eradication. It focuses on long-term prevention of pests or their damage by managing the ecosystem.
IPM is a five step process: 1) correct pest ID, 2) monitoring and assessing pest numbers and damage, 3) pest ID guidelines for when management action is needed, 4) preventing pest problems, and 5) determining correct control measures. Let’s take a look at each one.

#1. Pest ID

Correct ID of the problem-causing critter is the most important aspect of IPM. If you don’t know what you’re dealing with, how can you devise an effective control strategy, if indeed one is needed?
So what is a pest? Pests are organisms which damage or interfere with desirable plants or damage structures. Pests also include organisms that can impact human or animal health. Pests may transmit disease or may be just a nuisance. A pest can be a plant (weed), vertebrate (bird, rodent, or other mammal), invertebrate (insect, tick, mite, or snail), nematode, or a pathogen (bacteria, virus, or fungus).
A correct ID of the pest must be made before deciding if control is needed. If you aren’t sure you’ve ID’ed it correctly or want a second opinion, take a sample to your local Cooperative Extension Service Office.
Note: Be careful about asking for pest ID at a garden center. Employees may not be knowledgable, or your request might be seen as a sales opportunity. And think twice before taking the advice of someone who might try to sell you something.

It never hurts to ask for more input on an ID.


#2. Monitoring and Assessing Pest Numbers and Damage.

You’ve probably heard the saying, “The best fertilizer is the gardener’s shadow.” I’ll make the claim that “The best pest control method is the gardener’s shadow”.
For effective monitoring, you need to be out in your garden on a regular basis. Looking, listening, even handling plants, checking under leaves, etc., so you come to know it as well as you know the layout of your living room. You should have a good knowledge of your landscape’s microclimates, soil conditions, the path of sunlight through the year, how seasonal changes affect your garden and a general grasp of the climate. Once you know what’s “normal” for your landscape it’ll be easier to spot any abnormalities.


For example:
Your favorite rose always has a few aphids but the population seems to have exploded in the last few days. And why do some of them have wings?
Is that slug damage on that hosta?
You don’t recall seeing those rusty patches on that hollyhock before.
What are the odd black spots on this pomegranate?
Hmm….
Always ask yourself how extensive the damage is. Does it threaten the health or life of the plant, or is it largely cosmetic? Do you need more expert advice?
Continual monitoring and assessing of what’s going on in your landscape can help you decide if the damage is important or extensive enough to require pest management.

#3. Pest ID Guidelines to Determine if Management Action is Needed

Which one is the pest? They both seem surprised.

Using the biological information of the correctly ID’ed pest will help you decide if you need to deal with the situation. Here are some things to consider when deciding if management is needed.
Is the pest short-lived and is only in the garden for a few weeks or even days?
Does it only make a seasonal appearance?
Is the damage of long duration/the entire growing season, only for a short time and the plant recovers, or is the damage mostly cosmetic?
Is it a pathogen?
Does it carry a pathogen?
Can it cause irreparable harm?
Is it an invasive species that can or should be controlled?
Does it threaten a needed food garden?
Is the damage really that bad?

Knowing the life cycle and feeding habits of your ID’ed pest will help you determine if control is necessary. Use their biology against them. Do your homework.

So you have a plant issue and you’ve correctly ID’ed the pest and the problem. It needs to be dealt with.
What’s your next step?

“And you may ask yourself, “How do I work this…”?
Once in a Lifetime
by the Talking Heads


#4. Preventing Pest Problems

“An ounce of prevention is worth a pound of cure.” applies to landscapes as well our personal health.
Ask yourself if the garden problems you’re facing, most of which will be cultural, can be handled with preventative measures.
Are you over or under watering? This stresses plants which can attract pests.
Is the plant that is under attack in a less than optimal location? Can you move it or change its environment to help it become healthier? Or should you just remove it and let the Japanese beetles eat somewhere else?
Are you practicing good garden sanitation, are you cleaning up those camellia leaves and blossoms after they fall, are you turning that compost pile and ensuring it heats properly in order to kill pathogens or pests?
If your growing zone allows it, perhaps you could plant your summer squash or tomatoes later and avoid that first rush of squash bugs or hornworms? (Keep in mind that hornworms are larval sphinx moths which are an important bat food source.)
Have you tried using row cover to exclude problem insects or other pests?
Be sure you’re not causing the problem. A little garden evaluation can do a world of good.
The decision you make here will determine the road you take in dealing with your pest issue. You’ve identified the pest, done some sleuthing and have an idea of the scope of the problem in your landscape. Now you have to decide what is the acceptable level of this pest to have in your yard.
And as always, “Right Plant, Right Place”.

#5 Determining Correct Control Measures

Start at the base of the pyramid when choosing control measures

After analyzing the situation you’ve determined you need to engage in some form of pest control. But what should you use? Always strive to use the most benign yet specific form of control you can. Use the method which best targets the problem.
A combination of control methods usually give the best results. These include biological, cultural, mechanical/physical, and chemical/bio-rational measures. Start at the base of the pyramid (see above image) and work your way upward. Always allow sufficient time for methods to yield results. Pest problems rarely happen overnight. Early intervention is the key to control. See #2 above.


If you are forced to use pesticides always use them as a last resort, not as a first option.
Avoid using systemics on plants which are used by pollinators or other beneficial insects.
Avoid using broad spectrum pesticides and keep in mind that many pesticides which are approved for “organic” use are more toxic and less selective than “synthetics”.
An exception to the “avoid broad spectrum pesticides”: there can be times when a broad spectrum herbicide, such as glyphosate, is needed to kill both monocots and dicots. Use with care and follow label directions.

Always target the specific pest or problem.

To review:
Please follow the IPM Five Step Process:
1. Always ID the pest correctly.
2. Get to know your own landscape. Monitor and assess pest numbers and damage to determine if intervention is truly needed. It often isn’t.
3. Use the pest’s life cycle and feeding habits to decide if or when management action is needed. Use their biology against them.
4. Prevent pest problems in the first place. Be sure you’re not part of the issue. “Right Plant, Right Place.”
5. If necessary, determine the correct control measures and always choose the most benign method which will do the job. Keep in mind products labeled “natural” may not be the best or safest option. Avoid DIY concoctions. They’re usually ineffective, harmful and an illegal use of ingredients.

Garden smarter, not harder.

Want to learn more about IPM?
http://www.npic.orst.edu/pest/ipm.html
https://ipminstitute.org/what-is-integrated-pest-management/
https://www.usda.gov/oce/pest/integrated-pest-management
https://www.epa.gov/safepestcontrol/integrated-pest-management-ipm-principles
Regional IPM centers

And last but not least:
* Link to my favorite cover of this great George Gershwin tune

Water Woes

If you live in a place where water falls from the sky during summer this blog is perhaps not so helpful. However, gardeners in much of the western United States will suffer this summer from hot days (sometimes record breaking) and will need to irrigate their gardens and trees in order for them to survive impending drought conditions. The ongoing drought has drained reservoirs and flows of rivers are down or, in some cases, dry entirely. Due to water scarcity, purveyors are restricting water use outside of homes and in some cases curtailing all landscape irrigation. Using water wisely in the landscape has never been more relevant than now. In this blog post we’ll continue to explore saving our gardens from drought and touch on water use, water demand and plant stress.

Good news — Bad news

The good news is that the longest day of the year was last month. That means that the days are ever so gradually getting shorter. As days shorten, plants use less water. Water use is tied directly to photosynthesis and when the lights are out there is no photosynthesis. Shorter days mean less demand for water. The bad news is that we may have record breaking hot days ahead. Plants become susceptible to wilt, sunburn and dieback during very hot weather. The best way to prevent this is to ensure that roots are moist during very hot weather.

The combination of drought and heat caused sunburn to these privet leaves

Mediterranean Climate

It turns out that in Ventura, CA the longest day of the year is one of the historically driest months (least rainfall) and the shortest day occurs in a month with more rain than average. This is a classical Mediterranean climate, the rain falls when we least need it for thirsty plants. Plants may not use all the water that falls in winter but soil is leached of salts and deeper soil layers are filled with water. Large woody plants can utilize this deeper soil water in drier months.

In a Mediterranean climate little rain occurs in the summer months

Stress

What is not obvious is that stress, especially water stress, is not highest on the longest day but occurs and builds later in the summer and fall months. This is because water is slowly depleted from soils over time. Water use is compensated by irrigations during dry months so stress may not build depending on the effective use of irrigation to keep plants hydrated. Plants and gardens that are less reliant on irrigation build stress over time CUMULATIVELY until they are irrigated or rain falls again. So after the spring rains stop, the “stress clock” starts ticking and keeps building until rain or irrigation happens again in the fall or winter. It is no wonder that symptoms of stress such as wilt, sun burnt leaves, leaf fall and plant death occur in late summer when cumulative stress levels overcome plant physiological limits. Late summer often is the time when the hottest days occur and heat stress in addition to drought stress adds to the struggle for garden plants.

Adding stress bars (red) shows how stress builds over time if there is no rainfall or irrigation

Save your plants in the fall from deadly stress

In the late summer or fall months plants are most likely to die of drought induced stress. This can be forestalled by irrigation applied in August which will reset the stress clock to lower levels. Stress won’t return to low wintertime levels because irrigation water is often of less quality than rain water. The salts in the irrigation water raise the osmotic potential of soil water creating another kind of stress. When it rains, these salts are washed from soil and plants are at their lowest stress levels.

Monsoons (see recent blog by Pam Knox) provide arid climates with stress relief when plants growing in hot deserts most need it. Many plants come out of dormancy or germinate only after the onset of summer rains. While monsoonal moisture can be unpredictable usually some rain falls in the desert southwest. In years when the monsoons don’t come or provide only low amounts of water, some trees or other woody plants even cacti, may die from stress.

Monsoons in Portal, AZ, July 2022.

Monitor your plants for stress as long dry periods or hot weather get longer and hotter. Apply water strategically to take off stress. Irrigate deeply by soaking the root ball(s) of the plant(s) you want to save. Established plants are pretty tough and can survive adverse periods, newly planted specimens not so much. They must be irrigated frequently just like they were in the nursery until their roots are will grown into site soils. For those of us living in a Mediterranean or monsoon climate we should wait until the onset of a wet period is near before installing new plants.

People and Plants

This Independence Day weekend blog post is about John Bartram, the American gardener and botanist who revolutionized gardening.

John Bartram was born a third generation Quaker on a farm in Darby, Pennsylvania on March 23, 1699. While he had no formal education beyond the local school, he was interested in medicine and medicinal plants. Stymied by the lack of local medical schools, his interests gradually turned to botany and he became one of the first practicing Linnaean botanists in North America.

In 1728, Bartram purchased 102 acres of farmland and 10.5 acres of marshland along the Tidal Schuylkill River from Swedish settlers. After establishing his farm and building his house, he laid out his first garden across six or seven acres on a terraced slope leading from the house to the river. His farm and collections expanded over time and have since been recognized as the first botanical garden in the USA.


Bartram made many plant collecting trips, the first documented one to the “Jerseys and Schuykill mountains” in 1735. His many travels by boat, horseback, and on foot, took him to New England, south to Florida, and west to Lake Ontario. While traveling he collected seeds and plant specimens, assessing how best to cultivate them back home in Philadelphia and how to share his discoveries. Other Colonial-era plant nerds supported his efforts and shared unique plants from their own collections.

Through his seed and plant sharing network Bartram became associated with Peter Collinson, an English merchant, fellow Quaker, and Royal Society member. Collinson, also a plant lover, shared seeds and plants with fellow gardeners, many well placed in British society.

Encouraged by Collinson, who eventually became his chief agent in London, Bartram established an international trade in North American seeds and plants packed carefully in wooden “Bartram’s Boxes” which were shipped in the fall. For five guineas, clients received a container of generally 100 or more varieties of seeds, as well as occasional dried plant specimens and other natural curiosities like bird nests and rocks. Despite the hazards of a sea voyage, many arrived safely to their destinations, where they established a new palette of American colors and shapes within European gardens and landscape.

Bartram’s nursery business continued to grow and thrive with sons William and John Jr. joining the business. Bartram and William continued their plant collecting journeys around North America. In October of 1765, after becoming lost on one of their trips near the Altamaha River in southeast Georgia, they came across the “rare and elegant flowering shrub” Franklinia alatamaha. Of course they collected specimens, which is fortunate for us as the plant appears to be extinct in its original native range. It survives today in cultivation because of the Bartrams’ efforts (you can read this interesting article for more on the topic).

Franklinia bloom
Photo by Tom Potterfield licensed by CC BY-NC-SA 2.0

After lobbying by Collinson and Benjamin Franklin in 1765, King George III granted Bartram a pension of £50 per year as the King’s Botanist for North America, a post he held until his death. In this position, Bartram shipped his seeds and plants to the royal collection at Kew Gardens. Bartram also contributed seeds to the Oxford and Edinburgh botanic gardens. In 1769 he was elected a foreign member of the Royal Swedish Academy of Sciences in Stockholm.

John Bartram’s house as it appears today

Bartram, the “Father of American Botany,” died in 1777. His sons, William and John Jr,. continued the family business of North American plants after the American Revolution. A total of three generations of the Bartram family continued to operate and expand the botanic garden. It was considered the major botanic garden in Philadelphia until the last Bartram heirs sold out in 1850. America’s oldest surviving botanic garden was dedicated as a 50 acre National Historic Landmark in 1963. Be sure to visit when you’re in the area.

Interested in learning more about John Bartram and other revolutionary gardeners of his time? There’s an excellent book by Andrea Wulf, “The Brother Gardeners“. I highly recommend it.

ISBN-10 ‏ : ‎ 0307454754
ISBN-13 ‏ : ‎ 978-0307454751

Happy Independence Day and here’s to garden revolutions everywhere!

Franklinia alatamaha by William Bartram (1782)

How monsoons affect gardens

“Some people feel the rain. Others just get wet.”—Bob Marley

If you follow the weather news carefully, you might have noticed a little factoid in this week’s headlines: Mawsynram, Meghalaya, in northeastern India reported the highest all-time single-day rainfall in the month of June on the 17th. At 1,003.6 mm (39.5 inches), it eclipsed the previous highest rainfall of 945.4 mm (37.2 inches) recorded on June 7, 1966, according to the Guwahati-based Regional Meteorological Centre (RMC). The extraordinary rain fell as part of the Indian monsoon while other parts of the country are in drought and have received less rain than usual so far, although monsoon rains have been picking up. Seventy percent of India’s rain comes from the monsoon so if the monsoon fails, agriculture and water supplies are severely impacted.

A group of trees with clouds in the background

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Monsoon clouds in Himalayas. Source: Sitikantha kheti, Commons Wikimedia, 20 March 2018

What is a monsoon?

If you ask a layperson what a monsoon is, they will probably tell you something about very heavy rain and might even mention that it is a seasonal rain event. The most famous monsoon occurs in India each year, but monsoons are found in other parts of the world as well including China, Africa, and the United States. In the U. S., the Southwest Monsoon season usually starts in mid-June. If you look at the weather forecasts this week, it is right on time. This period is characterized by heavy showers and strong moisture flowing into the region bringing wet conditions to areas of the country that seldom see rain in other seasons. But officially, a monsoon is not the rain itself but a change in the atmospheric flow driven by differences in land-sea heating in summer. Rain falls in one half of the cycle but the switch to the opposite flow pattern often means dry weather as high pressure forces moist air away from the land.

Map

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7-day predicted rainfall on June 19, 2022, from NOAA.

How a monsoon forms

Monsoons are driven by temperature differences between land and water caused by heating from the sun. The hot land causes air over it to rise, leading to a net low-pressure area. Air rushes in from other locations to even out the pressure. On a small scale this type of circulation occurs as a sea breeze that you might feel along the shores of a large lake or ocean. The land heats up much more quickly than the water during the day, causing rising air over land that creates a circulating cell of air that blows cooler air from water to land in afternoon when the temperature difference is strongest. You can often feel a sea breeze front as the cooler air moves inland, and sometimes thunderstorms form along that boundary between land and marine air masses.

Diagram

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This diagram shows how seasonal temperature differences between the land and ocean can create the right conditions for a monsoon. Credit: NASA/JPL-Caltech

In a monsoon this pattern happens on a much larger scale. In Southeast Asia, for example, the whole of India and surrounding countries heats up under the direct summer sun much more than the Indian Ocean to the south. That causes air to rise over the land and pulls in air from the ocean to the south. In India, meteorologists track the progression of the monsoon “front” from south to north across the region and celebrate when the monsoon finally arrives, bringing copious showers that bring much-needed rain to India. In the Southwest U. S., the coming of the monsoon is also watched carefully because it provides welcome moisture and cooler temperatures to the region due to increased cloud cover. More than 50% of the annual rainfall of Arizona and New Mexico falls during the Southwest monsoon, so it is an essential part of the seasonal cycle. But it can also bring lightning strikes that spark forest fires in areas that receive little rain, causing widespread destruction in those areas.

Diagram

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During typical conditions in the spring, the U.S. Southwest experiences strong, dry winds blowing from the west. During a summer monsoon, the region experiences winds from the south, which carry moisture from the Pacific Ocean and the Gulf of California. This can cause heavy rainfall and thunderstorms. Credit: NASA/JPL-Caltech

How monsoons are important to gardeners

If you live in a part of the world that is affected by monsoons, you need to be prepared for the variation of rain over the course of the year. During the wet part of the monsoon, you may experience very heavy rains that can erode your garden and wash out plants. If you have low-lying areas, roots can be affected by standing water to the detriment of your garden plants unless you put in good drainage. Conversely, you need to also be prepared for periods with little to no rain at all, sometimes for significant periods of time. That means you either need to use plants that are adapted to the wet-and-dry monsoon conditions or be prepared to irrigate them regularly to keep them in good shape.

A tree with lightning in the background

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Rain in Mohave Desert. Source: Jessie Eastland, Commons Wikimedia.

Monsoons are one example of how earth’s geography, including sun angle, land-sea distribution, and differential heating all work together to create diverse climates across the globe. They have inspired local music and literature as essential elements of culture in India and other parts of the world. And they serve as a critical driver of plant life by providing needed moisture to growing plants and crops. So for those of you who live in monsoon climates, do a little dance when the rains begin. The monsoon is here!

Other resources:

British Meteorological Office video: What is a monsoon?

NOAA SciJinks: What is a monsoon

Monsoon video series of SW monsoon imagery set to music by Mike Olbinski—spectacular!

Chasing the Monsoon: A Modern Pilgrimage through India—my favorite book on tracking the monsoon through India

Tomato season is open!

Mmmmm, fresh summer tomatoes. They’re great sliced, diced or made into salsa or sauces. There’s nothing like picking one right off the vine, popping it in your mouth and splat! You now have tomato all over your shirt.
“No problem,” you think, “it’ll come out in the wash.”

Fast Forward to Laundry Day…

As you’re putting your freshly washed and dried laundry away you notice that tomato stain is still there. So you toss it back in the hamper for next time.
Several laundry days later, that tomato stain is hanging on. You decide it’s time to get serious.

So you soak and you scrub.
And you soak and you scrub.
And still that stain refuses to budge.
(Rather poetic isn’t it)

You’re about to go all Lady MacBeth on it!

Out, damned spot! Out, I say!”
The Tragedy of MacBeth, act 5, scene 1

But thankfully you regain your senses before ruining the shirt.
“What’s the deal with this *&#^%*$ tomato stain!” you wonder. You’re almost ready to designate it your “special tomato shirt,” which admittedly would be handy for those “S’ketti Night Socials” at the county fair, but you’re not quite ready to give up yet.

Nil desperandum my friend! Professor Sprout has some special botanical knowledge to impart that will make your Expelliarmus spell work.

Why Are Tomato Stains So Difficult To Remove From Fabric?

Tomatoes contain multiple pigments: chlorophyll, carotenoids, xanthophylls, and betacarotene. The trouble maker is a bright red carotenoid, lycopene. It’s an approved food coloring and is found in other red fruits such as watermelon, red carrots and papaya. Despite it’s being a carotene, it has no vitamin A properties.

Lycopene

Why Does Lycopene Stain?

Lycopene is not a water soluble pigment, it’s only soluble in fat. In other words, it’s hydrophobic. Hydrophobic molecules cling together to minimize their contact with water, so the pigment hangs onto whatever surface it’s on. Add the nooks and crannies of fabrics, especially natural ones, and it’s hard to get it to release its hold. The hydrophobic nature of lycopene also means that it resists attempts to clean it with just soapy water. The high temperatures of a washing machine can drive stains even deeper.

Nope, that water ain’t gonna touch me!


So, How to Remove a Lycopene Based Stain?

The trick to removing a lycopene based stain from fabric is to treat it like a lipid stain (lipid = fat or oil). Bleach won’t work and often regular spot treatment or laundry detergent won’t either. If it’s an old stain you might need to put a drop of regular cooking oil on the stain or spritz it with an oil based pan spray. What you’re wanting to do is get the lycopene back into an oil base which can then be washed out.
Another thing that works is to hit the stain with a solvent based stain remover. There’s a popular brand of carpet cleaner that works quite well for this. We can’t make commercial recommendations here but if the name Sp*t Sh*t rings a bell well, aren’t you clever. As with all stain removers test on an inconspicuous area beforehand.
If the stain has been through several wash loads, it make take a few wash loads to remove it. But the above method will work.

Cleaner clothes, with botany!

Bonus round!

Lycopene also stains plastic which is why the container you reheated the Aunt Mamie’s spaghetti sauce in is red. The good news is that lycopene will oxidize so you can soak the stained plastic with a bleach solution which should remove it.

A little soak with a bleach solution will remove the ‘mater stain.

So there you go. Enjoy tomato season and don’t worry about the laundry!

Johann Weinmann “Tomatoes” 1737-45

Saving Your Trees From Drought!

Yikes!

Drought of epic proportion is imperiling many western states this year. For the first time some water districts have proposed curtailment of all exterior irrigation, no applied water will be allowed outside of residences. There are public forums are scheduled with experts and officials giving advice. Of great concern is the certain loss of turfgrass swards but far more concern is being expressed for the loss of trees.

Drought brings change in landscapes. Here European birch have died and provide opportunities for planting more drought tolerant species

Don’t assume your trees will die of drought!

Most established trees are resilient, they have built in drought avoidance and tolerance strategies. It helps to understand these processes and know the symptoms of drought injury in trees. Almost all trees will stop growing when they enter drought conditions because there is not enough water to produce the turgor pressure necessary to expand cells. While growth may slow, trees have root systems that help prevent them dying of drought. The root systems, while mostly in the surface layers of soil, also explore greater depths where they can extract water from larger volumes of soil. So even though soil may be dry on top, trees have greater access to moisture than is obvious from above. Trees also have mycorrhizal fungi that help them extract water bound tightly to soil. When these strategies become limiting, tree roots produce abscisic acid that flows to the pores in leaves and closes them to reduce transpiration. If drought continues, many trees will drop leaves entirely to help stem and root tissues survive, thus avoiding drought. These mechanisms are all controlled by tree genetics and their ability to ameliorate drought effects is variable. Some trees are just more drought resistant than others.

Some trees such as this Indian rosewood (Dalbergia sissoo) are adapted to hot climates and endure long dry periods without damage.

Don’t plant new trees in the Summer!

Now is not the time to plant trees. As we near June 20th (the longest day of the year) demand for water is also greatest as sunlight drives photosynthesis and thus water use by trees. Newly planted trees all need irrigation to help them establish. During drought years, wait until later fall months (when rain is more likely and day length is decreasing) to schedule planting.

Don’t fertilize trees during drought!

Fertilization is the last thing you want to do during or at the onset of drought! Fertilizer (organic or inorganic) contains salts that increase the osmotic potential around roots. This alone can create “physiological drought” as water is drawn out of roots into soil solutions. Fertilizers should only be applied when known deficiencies are present and water is abundant enough to dissolve the applied materials.

Fertilizers increase drought stress for trees if water is not available for the application.

Don’t prune trees during drought!

Pruning removes terminal buds that regulate growth of the canopy. When they are removed by pruning, lateral buds are released to grow. Stimulating new growth during drought is a disaster for trees. Don’t do it! You may falsely think removing branches in a tree canopy will save water. Most trees can regulate their own water loss as discussed above or by dropping leaves as necessary when dry conditions ensue.

Pruning, especially over-thinning, stimulates new shoots to grow–something you do not want to encourage during drought periods

Do not install artificial turfgrass

Artificial turfgrass is not a solution for hot dry conditions. In some cases it may exacerbate the situation. Artificial turfgrass does not allow percolation and capture of water since it covers soil. Artificial turfgrass does not transpire, so landscapes will not be cooled by it. Trees adjacent to artificial turfgrass have less ability to access water than those adjacent to a mulched area.

Artificial turfgrass does not use water but it also gets hot. On the day this image was taken it was 50 degrees hotter than irrigated turfgrass and 30 degrees hotter than brown dry turfgrass

The longest day in June may not be the most stressful for trees

When water is scarce, it is important to apply it strategically to reduce tree stress. Even though June has the longest day and potentially tress will transpire the most, it may not be the most stressful time for trees because water may still be available at lower soil levels in June. As we enter later summer and early fall, stress builds as available water is depleted from tree root zones. Deciduous trees will lose leaves but evergreen trees or trees that can’t shed their canopy may begin to enter their permanent wilting points. This is usually proceeded by wilt, dieback, and loss of color. This is a critical point where strategic water applications can help trees through a critical period.

Do apply Arborist Chip Mulches

Mulch is a critical drought survival tool for trees. It is best if mulch is already in place but it is never too late to apply it. Mulch changes soil structure allowing for more water storage. Over time, mulched soils become more drought resilient. In the short term mulch prevents evaporation from soil surfaces so that applied water stays applied in the soil and is not lost. Coarse wood chip mulches prevent weeds that use water thereby keeping more moisture in the soil. Wood chip mulches support the mycorrhizal fungi that help trees survive.

A common theme in these blogs: arborist chips straight from the chipper have real benefits for trees trying to survive drought

Do “top up” existing mulched areas around trees

Mulch breaks down as it is supposed to. It is important to keep mulch layers intact by occasionally adding to mulch layers. If you have not done so, add mulch before summer gets too far along.

Do remove lawns or shrubs that are no longer sustainable in the landscape with care.

Due to climate change, coast live oak (a native) is less adapted to inland valleys of Southern California than Eucalyptus camaldulensis (an exotic).

Water restrictions, hot weather and dry soils culminate and can greatly damage landscapes. If landscapes are over planted or there are unwanted/unnecessary plantings they can be removed to save the water they would use. Be careful not to expose existing plants and trees to bright sunlight as this may cause them harm from sunburn. Be careful removing turfgrass swards and the irrigation that accompanies it because adjacent trees may be reliant on the excess applied water. A slow dry down and mulch over process may be the best approach to save valuable perennial plantings near unsustainable turfgrass.

Do monitor your trees for signs of impending drought stress. and apply water in a timely manner

High temperature injury to cherry leaves is not a symptom of drought but heat intolerance. However, as trees dry down they have less ability to endure high temperatures.

Wait until leaves start to turn yellow prematurely or canopies show wilt symptoms to apply water. As drought symptoms develop, consider a slow application of water by a dripping hose (moved frequently) or a low flow sprinkler that applies water only as fast as the soil can take it in. Apply water at night to cut down evaporation loss. Continue to monitor for further drought symptoms and spread out irrigation as needed to conserve water.

Do turn off your valve controllers to avoid over application of water.

Don’t let electronic devices make irrigation decisions for you during water restrictive drought periods. No electronic system completely understands the stress conditions around trees and will not be able to accurately predict when to irrigate. It is best to make these decisions based on your own assessment of conditions and resources available. Many “irrigation clocks” rely on regular frequent applications of water to keep soil moisture supplied. Frequent short run cycles replace water used by plants. During drought restrictions, controllers need to be reprogrammed to apply less frequently but for longer runs (to the point of run off) or not used at all if the sprinkler emitters put out too much water. Targeted water applications will likely be necessary and valve controllers will need to go “dormant”, i.e., turned off.

Be hopeful

Droughts come and go, right now they keep coming. But there are many examples of trees that only receive rainfall, no applied irrigation and yet survive well. Don’t assume your trees will die of drought. This may be a time to remove trees that are not adapted to growing in your area and drought conditions will reinforce this. European Birch are certainly disappearing from many landscapes this year in Southern California. Increase the use of mulch, apply water strategically, and consider planting more adapted trees late in fall or winter when water is available to support establishment.

Monitoring and reporting on drought conditions

While drought is part of the natural cycle of the climate and many native plants depend on drought to propagate, it is the bane of gardeners everywhere because of the increased need for water. I have previously written about the four types of drought. Today I thought I would focus on drought monitoring and a way that you, as a citizen scientist, can help report local conditions that the official drought monitor authors can use to fine-tune their depictions of drought. This will be especially helpful this year with so much of the country in drought conditions.

A picture containing sky, outdoor, water, nature

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Desert bounty. Source: GTGallop, Commons Wikimedia

What is the Drought Monitor?

The U. S. Drought Monitor (I’ll call it the DM here) is the source of the “official” drought status across the country. Of course, you don’t need an official status to be in drought but it is commonly used by media, government agencies, and scientists to categorize the strength of drought over time and space. The official DM map shows a single map for the United States updated each Thursday morning that is color-coded by five levels of dry conditions ranging from Abnormally Dry (D0) to Exceptional Drought (D4). The drought categories show experts’ assessments of conditions related to dryness and drought including observations of how much water is available in streams, lakes, and soils compared to usual for the same time of year. If there is no color shown then that region is not officially in drought. If it is in D0 (bright yellow on the map), then it is considered dry but not currently in drought. Often a D0 designation means either that drought is imminent or that there are lingering impacts from a drought that is ending. You can read more details about what kinds of impacts are seen in each level of drought and how the weekly map is produced on their “About” page. You can also find links to state-specific impacts there, since a drought in the Southeast does not look like a drought in the Southwest, for example.

National Drought Monitor map for May 24, 2022.

Issues with the DM

One of the shortcomings of the DM is that there is just one weekly map that is supposed to be a complete depiction of drought across the United States. If you read my last post on drought, you know that drought comes in different varieties that occur over different time periods. Agricultural droughts are caused by dry spells and hot temperatures during the growing season and can come on very quickly (“flash droughts”), while the long-term precipitation averages might not reflect that lack of water and so would not be captured on the DM map. Hydrological drought is related to a long-term lack of rainfall that reduces the water levels of lakes, streams, and reservoirs over many months or even years. It might not affect gardens and farms significantly as long as enough rain falls at regular intervals to keep the plants alive.

While the DM was not created to be a legal means for defining drought, it has become one in legislation passed by Congress to provide drought relief to affected farmers. The program I deal with the most in my work is the Livestock Forage Disaster Program, which provides a payment to forage producers to offset economic losses if drought stops the growth of pastures, especially early in spring when hay supplies are depleted over the winter. The law is written in such a way that if the drought level is severe drought or worse (D2+) for eight consecutive weeks, then they can receive one month’s payment for the lost forage. If it is in extreme drought (D3) somewhere in their county for any time during the growing season, then they can get payment for three months.

Dry pasture in Oglethorpe County, GA. CMOR report by BWF, May 2022.

As you can imagine, when a flash drought happens and the grass stops growing the forage producers need the relief to help purchase hay to keep their livestock alive. But the DM does not typically depict this quick-changing drought because it is based on longer-term indicators that do not change much over just a couple of weeks. So there is a disconnect between what the DM is showing and how it is being used for legal purposes, at least in the case of forage and pastures.

As you might guess, this results in some attempts to game the system to make it look drier than it is to get the DM authors to declare a D2 or higher drought. The authors tell stories about being harassed over the phone about where they draw the drought lines on the map, finding observers who report no rain when radar clearly showed it occurred, and other creative ways to make the drought appear worse than it is so they can get access to the payments they need.

How can you monitor and report drought?

Here is where you come in: Citizens like you have an important role to play in keeping an eye on local vegetation and monitoring it for signs of drought or impacts from saturated soil. Gardeners are already especially attuned to what conditions are normal and what conditions are not. Folks who monitor local climate conditions are much like storm spotters who monitor weather systems for strong winds and tornadoes—they watch how things evolve over time and provide that information to the authors of the DM and others who need hyper-local information, although on a much longer time-scale that storm spotters. If you are a CoCoRaHS rainfall observer, you probably already know about the Condition Monitoring report that you can submit through their website. Another great place anyone can submit official Condition Monitoring Reports (called CMOR which is pronounced “see more”) is the CMOR site on Drought.gov.

Condition Monitoring Reports for the 30-day period ending on May 24, 2022.

As you can see from the map above, there are many parts of the country with no CMOR reports to provide information about conditions at those spots. By providing these reports, you are helping the DM authors with unbiased, fact-based local observations that can support other drought indicators like streamflow, precipitation deficits, and groundwater losses. Thanks for providing this service to the DM authors and other scientists!

A picture containing grass, outdoor, sky, nature

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Lake Powell, Desert Flowers. Source: Don Graham, Commons Wikimedia. He says: “What’s left of Lake Powell is between this stand of wildflowers and the buttes in the distance. It is, sadly, more like a pond now than like a lake.” Even the desert can be in a drought if the rainfall is much less than expected!

Maddening mulch myths

A good example of bad mulching

Long-time followers of this blog know that I’ve been researching, writing, and educating on the topic of landscape mulches for over 20 years. So whenever an article comes out in a newspaper or online that directly refutes our current understanding of mulch science, on-line and real-life colleagues quickly call it to my attention. Many times I choose to ignore the article, but when it’s from a highly regarded source with wide readership I feel the need to step in. Before I discuss the problematic statements, I want to explain part of my process in determining whether an expert is really an expert.

Here are two questions I ask:

  1. Is an expert regarded as an expert in the area of interest by other academic experts?
  2. Is there published research provided that supports statements that don’t agree with the current body of knowledge?

If the answer to both questions is no, then the source cannot be considered reliable.

This free, downloadable, peer-reviewed resource can help you learn how to differentiate bewteen credible and not-so-credible information.

To the writer’s credit, she seeks out academic sources for her information. Her source has stellar credentials in researching and educating about compost, but has no publications on mulching or mulch materials (Question #1 = no).  And there are source quotes and author statements throughout the article that are not supported with evidence (Question #2 = no).

I’ve identified the misleading or erroneous statements and quotes below with my rebuttals. I have included linked references at the end that address these points in more detail. And we have dozens of posts on mulches in this blog’s archives.

Just type “mulch” in the search box and find all kinds of good stuff!

1. “In a forest…there is no big heap, just a layer of an inch or two or three, breaking down and returning to the system.”
Observations of relatively undisturbed forest floors reveal deep layers of woody debris, leaves and needles, and other materials falling from the canopy. Research has shown that a minimum of 3 inches of a coarse textured mulch are needed to restrict sunlight from reaching the soil and prevent weed seed germination. Any less than this will enhance, not prevent, weed growth. Deep layers of wood chips have been repeatedly shown to suppress weeds and enhance the health of desirable plants.

This is what an inch or two or three will do for you.

2. “The process releases humates…described as ‘black, gooey liquid’…”
Humates, defined as recalcitrant materials that resist further decomposition, don’t exist in natural landscapes. The only place you find humates are in the lab, where analysis of organic material with an alkaline reagent (pH = 12) produces humus as a byproduct. And on garden center shelves, where heavily marketed humic acids, fulvic acids, and humates are located.

3. “The only difference in mulches, as long as you use organic materials, is the rate at which they decompose”
This needs clarification. Rapidly decomposing mulches release high levels of nutrients in a short period of time; slowly decomposing materials release low levels of nutrients over longer periods of time. Compost falls into the first category, and readily available nutrients from any source can lead to nutrient toxicity in soils and imbalances in plants.

Interveinal chlorosis is often associated with excessive soil phosphorus.

4. “In formal beds…fine- to medium-textured material”
For best oxygen and water movement, mulches should be coarse and chunky. Sawdust and compost, for example, are too finely textured to allow for gas transfer and water movement, plus weeds easily establish on top of compost.

Compost used as a mulch is a weed magnet.

5. “If a bed needs compost, spread an inch before mulching”
This statement needs clarification. The only way you know whether compost is needed is to have the results of a soil test showing an overall low level of nutrients. Then a layer of compost could be added before chips are applied.

If your nutrients are off scale, don’t use compost!

6. “Save…the chunks fresh out of the arborist’s chipper for pathways…Or at least pile them up to mellow before you use them.”
You don’t need to compost your arborist chips. They provide a burst of nutrients during the first month, when leaves are rapidly decomposed. Using older chips is fine, of course, but why waste that early nutrient boost to your soils?

There’s nothing better than fresh arborist mulch straight out of the chipper.

7. “If supplemental fertilizer isn’t applied when your piling on coarse, fresh, carbon-rich wood chips…it can cause some drawdown in soil nitrogen.”
Fertilizer should NEVER be applied unless there is a demonstrated nutrient deficiency, and wood chip mulches do not cause a drawdown in soil nitrogen. This myth has been dispelled by years of research showing no change to soil nitrogen covered with wood chips.

If wood chips cause a nitrogen deficiency, then plants apparently haven’t gotten the message.

8. “Generally, mulch is applied in ornamental beds at a depth of one to three inches”
See point #1. This is not a science-based recommendation.

9. On volcano mulching: “In addition to promoting bark decay, it causes the tree’s roots to grow up into the mulch layer, rather than down into the soil…the tree may eventually die, and even topple.”
This classic correlation-elevated-to-causation is getting tiresome. There is NO published evidence, anywhere, that proper mulches (i.e., coarse arborist chips) are going to injure bark. They do not cause bark decay. Furthermore, tree roots grow where they have water, nutrients, and oxygen. This might be in the mulch layer. Growing deep into the soil is unlikely (not enough oxygen) unless the soil is excessively sandy or otherwise well drained. Any toppling of trees can be directly correlated with poor planting techniques that prevent roots from contacting and establishing in the site soil.

10. “Keep the mulch at least several inches away from tree and shrub trunks.”
Why? Does this happen in nature? No. Per point #9, a natural woody mulch is not going to hurt trunks.

The soil of this lush landscape is completely covered with a thick layer of arborist chips.

11. “And don’t invite rot by smothering the crowns of perennials”
A good arborist chip mulch is not going to “smother” anything. Perennials are quite capable of growing through several inches of woody mulch, which also protects the crowns from freezing temperatures.

Our perennial rhubarb thrives in its deep arborist chip mulch.

If we are going to encourage gardeners to use nature as a guide (see point #1), then points 4-11 are, well, pointless.

Literature

Chalker-Scott, L. 2007. Impact of Mulches on Landscape Plants and the Environment — A review. Journal of Environmental Horticulture 25(4) 239-249.

Chalker-Scott, L., and A. J. Downer. 2020. Soil Myth Busting for Extension Educators: Reviewing the Literature on Soil Nutrition. Journal of the NACAA 13(2).

Chalker-Scott, L., and A.J. Downer. 2018. Garden myth busting for Extension educators: reviewing the literature on landscape trees. Journal of the NACAA 11(2).

Lehmann, J., Kleber, M. The contentious nature of soil organic matter. Nature 528, 60–68 (2015). https://doi.org/10.1038/nature16069

Burlap, the fashion fabric of the gardening world.

Cheap, lightweight and easy to manipulate, burlap has become a popular way to protect transported B&B trees from the nursery to their planting site. To add justification for its use it’s also touted as biodegradable. “No need to remove it!” or “Leave it in place to protect the root ball.” and other such phrases are often tossed at the unknowing homeowner but are they laudable? Let’s investigate.

Hessian soldiers ca. American Revolutionary War – what do they have to do with burlap?

Carl, J.H., “Regiement von Bosse” (1784). Prints, Drawings and Watercolors from the Anne S.K. Brown Military Collection. Brown Digital Repository. Brown University Library.

Burlap is the North American name used to refer to a fabric known as hessian in other parts of the world (except in Jamaica where it’s called crocus.) “Hessian” is attributed to the historic use of the fabric as part of the uniform of soldiers from the former Landgraviate of Hesse and its successors, including the current German state of Hesse. Soldiers from these areas were called “Hessians”. If you recall your American Revolutionary War history, the name Hessian might ring a bell.
While the word burlap might bring to mind the image of a coarse brownish material, Hessian fabric is available in different types of construction, form, size and color. Even though the two names refer to the same fabric, we’ll stick with “burlap” for our discussion.

Illustration of Corchorus olitorius, 1828, William Jackson Hooker (1785-1865)

Burlap is produced from two Corchorus species in the Malvaceae family. The main fiber source is C. olitorius but the fiber from C. capsilarius is considered superior to it having a finer texture. Both plants are called jute, which also applies to the fiber.

Jute grows best in a warm, wet climate. A long monsoon season followed with consistent temperatures over 75ºF/ 25°C and relative humidity of 70%–90% are ideal. Jute requires 65″-80″/160–200 cm of rainfall yearly plus extra during the sowing period. The plants prefer river basins, alluvial or loamy soils with a pH range between 4.8 and 5.8. Periodic flooding or marshy conditions are well tolerated. ~85% of the world’s jute is grown in the Ganges Delta.

Farmer collecting bundles of harvested jute to be taken for initial processing in West Bengal India. CC image

When ready to harvest, the jute is cut off at the soil surface and gathered into bundles for transport and processing. To extract the fiber, the jute bundles are retted. There are a variety of retting processes: mechanical (hammering), chemical (boiling & applying chemicals), steam/vapor/dew retting, and water or microbial retting. Water or microbial are the oldest forms and most often used.

Jute bundles being water retted. The bundles are kept submerged with logs. CC image

When the jute is well retted, the bundles are hit with a long wooden hammer to loosen the fibers from the core. After loosening, the fibers are washed with water and squeezed dry. The extracted fibers are further washed with water then hung up to dry. When dry they’re tied into bundles to be sold at market.

Jute fibers drying. CC image
Jute market. CC image

So what does all of this have to do with B&B trees?

Image by USU Extension

Burlap, even a tightly woven burlap, “breathes.” This gives it a strong resistance to condensation, moisture, and fungal growth. Jute is a hard fiber which makes it very durable and jute burlap is wear, tear, puncture, and stretch resistant. Breathability plus condensation, moisture, fungal growth, wear, tear, puncture and resistance to stretching are all qualities which make burlap a good choice for the transport and storage of goods and as a geotextile.

“Natural” burlap is lightly treated with an emulsion, usually a cheap plant based 3:1 water and oil mixture, as a part of the weaving process. The mixture makes the fibers easier to handle and move through the loom, and helps reduce waste. The water does most of the work; the plant-based oil just prevents the water from evaporating so quickly. Burlap made with plant-based emulsion is required for food safety, storage and transportation and aren’t as long lasting as the other type of burlap. They normally last about three years in use but can take up to a decade to decompose.
Yes, you read it correctly.
“Natural” burlap can take 10 years to fully decompose.

Burlap sacks of green coffee beans.
Image credit: Tim Pannell, Mint Images/Science Photo Library
 

The qualities that make burlap good for food stuff transport also make it useful in the construction, landscape, government/emergency services, and outdoors/sporting sectors. Fabric woven for use in these areas is treated differently; the emulsion used on it during weaving is usually petroleum based. This emulsion is designed to add more water, rot, and gnawing pest resistance to the fibers prior to weaving. It can leave the fabric feeling “sticky” or “coated” and tends to attract dust and dirt. It also has a peculiar chemical aroma to it. The finished fabric is often treated again to add even more resistance. So, the fibers are treated prior to weaving and then often again afterward. A double whammy, so to speak. “Treated” burlap is very long lasting, durable and can be stored for years in a variety of conditions without the fibers weakening. It can last for decades, above and below ground.

A hay bale ground blind covered with water and wind resistant burlap.
We didn’t know this was a thing.

Which brings us back around to B&B trees.

Image credit: Matt McClellan

Guess which burlap is used almost exclusively in the landscape industry, the “natural” or “treated” ?
If you guessed “treated,” you’re correct! Its durability, ease of use, and excellent storage qualities makes it the #1 choice for transporting nursery trees.
Unfortunately many, if not most, plant people don’t know about different burlap types and are relying on out-dated information. (This is true in more areas than just burlap, but those are other issues.)
Try asking if the burlap on that root ball is “natural” or treated and see what their response is. Feel the fabric yourself. Does it have a tacky feel, do your fingers drag on it, does it seem to attract dirt or dust? Does it have a chemical or petroleum odor to it? These are all indicators of treated burlap. Both natural and treated burlap degrade slowly. Leaving burlap on the root ball will only encourage circling roots and probably doom the tree.

Just so we’re not being misunderstood: Wrapping the root ball with burlap for transporting purposes is all well and good.

But you have to remove it at planting!

Let’s do a quick review of the qualities of burlap and how they can backfire when planting trees.
Breathability: not really a problem underground but can cause the root ball to dry out if the tree is exposed to the air for too long.
Condensation and moisture resistant: doesn’t absorb water so the fibers won’t rot.
Little to no fungal growth: isn’t consumed by fungi so fibers stay intact.
Tear and puncture resistance: roots can’t push or force their way through therefore encourages circling roots.
Doesn’t stretch: won’t expand with root growth therefore encourages circling roots. Sound familiar?
Natural” burlap: can take up to a decade to completely decompose all the while negatively impacting root growth.
“Treated” burlap: can take decades. ‘Nuf said.

Bonus round!
Soil factors can also influence burlap decompostion. The decay rate in soil pH levels below 6 is significantly slowed. Low soil temperatures result in a slower decomposition process. Dry soil slows jute fiber break down too and even desert termites don’t care for treated burlap.

A B&B tree is an investment: give it the best possible start you can. Always remove the burlap, wire basket, strings, ties, or any other constrictions you find. And don’t forget to root wash, correct any root problems, and spread the roots out horizontally away from the trunk when planting.

Image credit: George Weigel

For your enjoyment, be sure the sound is turned up so you get the full effect.
https://youtu.be/D9AUnYTol68