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

Garden Diagnostics

A garden plant with symptoms of an insect infestation

I’ve had this funny feeling that something is just not right in my garden. Can’t put my finger on it, but something is amiss. OMG everything is dying! Help! Garden Death is rampant! Well, a bit of hyperbole perhaps, but over the years I have had many calls from gardeners with great concern for plants or their entire garden based on things they perceive to be going on. I have helped them by trying to diagnose their problems. Thought occurs though that most gardeners should be able to diagnose their own garden problems with guidelines and framework that informs their decision making processes. The problem with solving problems is that often gardeners don’t notice a problem until it has advanced quite far often to the point of no return. So, the trick is to “see” things early so they can still be fixed.

Looking for patterns in your garden can inform disease issues. here all the boxwood are yellow and all the redwoods are brown. See first paragraph! Yikes!

Patterns

The first step to solving garden problems involves looking for patterns in the symptoms that are presenting as the “that does not look right to me” situation. The redwoods and boxwood in the image above are all performing badly and the symptoms are uniform. Uniform symptoms that occur across a population of plant often suggest an abiotic cause. In this case the use of recycled water high in salts has impacted the landscape plantings.

Symptoms are plant responses to a pathogen or abiotic condition

Symptoms

are plant responses, changes in physiology such as chlorosis, and necrosis, spots, coloration or discoloration etc. Foliar symptoms often form when a plants ability to make or utilize chlorophyll is compromised. Symptoms also occur on stems in the form of cankers or dead spots that can ‘girdle’ the stem leading to foliar symptoms in the shoots on that stem. When diagnosing garden problems it is important to look at symptoms carefully and early. This involves understanding what is normal for the plants being grown. Plants exhibit a variety of growth patterns and changes throughout the season so some changes are normal. The trick is to see the early onset of “not normal” symptoms.

Signs are the actual pathogen that is causing the symptoms in the affected plant

Signs

…are the cause of disease. Signs often confirm a diagnosis and give way to control options once a pathogen or other disorder is identified. Finding signs is of the confirmation needed to take some action to fix the problem in the garden. Often fruiting bodies of pathogens don’t form until the host has died or shed leaves that fall on the ground. Many signs are microscopic, but some spores can be seen ‘en-masse’ when inocculum builds up to visible levels. And sometimes symptoms and signs occur together helping to solve the diagnostic problem.

Powdery mildew spores (white) are signs and the broom-like symptoms are typical of the disease that forms in coast live oak.

Canker diseases cause a variety of symptoms and signs. Most cankers only form signs after the stem has died. Early in the progress of disease plants may appear discolored but it is not until later that the signs will form usually after the plant is visibly necrotic

Early symptoms of Ficus canker in Indian Laurel Fig
advanced symptoms of Ficus canker
Signs of Ficus canker disease. The black dots forming on the end of a cankered branch are fruiting bodies that hold the spores of the fungus causing the disease.

Time

…is an important factor in disease progression. Diseases do not happen instantly but form over time. Diseases, if they result from pathogens, have a “life history” where the various stages of the pathogen are formed or survive and accompany symptom development in the host. Early symptoms may be innocuous or subtle. The problem is we notice problems at a single point in time but the problem is often well along or has been developing long before we notice it. Understating the time line of disease or pest formation is important in diagnosing the cause.

Insects

—are often confused with pathogens because they can cause some of the same symptoms as plant pathogens or abiotic disorders. Insects cause an array of symptoms that can be used to diagnose their presence. Some insects related symptoms are: foliar stippling, bronzing and bleaching, leaf spots, chewed foliage, wilting and death of branches or entire portions of a plant or tree and galls. Insects also create signs of their activity such as frass, galleries, honeydew, cast skins, and excrement. Of course the ‘gold standard’ of insect signs is the insect itself which can take the form of adult insects or larval insects, both of which may look very different and affect different parts of a plant.

Frass shown here is a sign of boring insects inside this tree.
Many insects cause their host to grow galls such as this oak apple gall caused by a small wasp
This leaf spot on Lantana camara was long thought to be a fungal disease but is actually caused by a ‘blotch miner’ insect in the genus Liriomyza.

Diagnosis of garden enemies is just the first step in finding a solution to a garden plant malady. Often determining the cause requires some expert help. Your local Cooperative Extension advisor often has experience in diagnosing the most common problems or can find assistance getting answers. With the advent of smartphones that have great cameras we can diagnose many issues remotely with images. Regional expertise is best as pests vary by state and region. The diagnostic prowess is often local–in the county where you live. Start there and widen your research until you feel you have the identification you need to research possible cures.

What a third year of La Niña means for gardens

NOAA recently announced that La Niña is favored to continue through summer and fall this year and could last through next spring. This forecast is bound to strike fear in gardeners in the western United States, since La Niña is associated with drought in the western parts of the country which sorely needs more rain. Los Angeles has announced some stringent watering restrictions due to impending water shortages, and that means gardeners will have to be especially careful there to use the water they have wisely.

Los Angeles Air Force Base uses xeriscaping to conserve water. Source: AF_SMC., Commons Wikimedia.

What is La Niña?

Many people have heard the terms La Niña and El Niño but for those who don’t, let me take a few minutes to describe them. You can also read more in my blog post from last fall when this winter’s La Niña was just getting going. El Niño and La Niña are two opposite phases of an oscillation in the atmosphere and ocean in the Eastern Pacific, with neutral conditions in between the two phases as the oscillation swings back and forth like a seesaw. When that region’s sea surface temperature is warmer than usual near the equator, rising air above the warm water creates thunderstorms which act like a rock in a river diverting the flow of air along the southern US, especially in winter when El Niño and La Niña are usually strongest.

Source: NOAA.

In El Niño winters, the Southeast is usually wetter and cooler than usual due to the presence of the subtropical jet stream overhead. It pushes storms with their associated rain and cloudy conditions through the region, recharging soil moisture for the next growing season. In La Niña winters, the jet stream is shifted to the north over the Ohio River Valley, leaving the Southeast warm, dry, and sunny. That means conditions for severe weather are more favorable in the Southeast than in other phases; we have certainly seen plenty of that this year so far. The lack of a strong jet stream also means that tropical activity in the Atlantic Ocean is more frequent and stronger than in El Niño years. In northern parts of the country La Niña winters are usually cold and snowy with a late start to spring, as we have seen this year. The Pacific Northwest is often wet, which also matches what has occurred in their coastal areas this year.

The ENSO Index shows El Niño periods as positive values (in red for warm Eastern Pacific ocean temperatures) and La Niña periods as negative values (in blue for cold ocean temperatures). Index values between +0.5 and -0.5 are considered neutral and are highlighted with gray.

How often does a third year of La Niña occur?

The atmosphere usually swings back and forth between El Niño and La Niña roughly every 3-5 years. Right now we are ending a second consecutive winter of La Niña; with its predicted continuation, that would make it three years in a row. This is not unprecedented, but it is certainly unusual, since 1950 we have only had two “triple-dip” La Niñas. Since there are so few direct comparisons it can be hard to determine exactly what to expect this growing season and on into fall and winter. Our best bet is to assume that typical La Niña conditions will occur. The 3-month composites of the expected anomalies (differences from average; MAM means March-April-May, etc.) show the seasonal variability of El Niño and La Niña for temperature and precipitation across the US. La Niña and El Niño’s effects stretch far beyond the US and affect global weather patterns.

What does this mean for the growing season across the United States?

Typically effects from a La Niña are weakest in the summer because sea surface temperature anomalies are not strong and is often switching from La Niña through neutral conditions to an El Niño the next year. However this year the La Niña is still going strong, so this seems less likely. That means the pattern of warm and dry southern states are likely to continue, which is trouble for the already drought-ridden Southwest including California (where severe water restrictions are now in place). With the high temperatures, low rainfall, and low humidity, that means water stress on gardens will be higher than normal, and drought and wildfires could dominate that part of the country for the next few months.

In the Southeast, the active spring severe weather season will likely give way to an active tropical season in summer and fall. Rainfall in the Southeast in summer is dominated by tropical systems and small-scale convective rain events that provide only hit-or-miss rain. If you are in the path of a tropical storm, you can experience several inches of rain while areas a few counties away can see none, resulting in a feast or famine of rain. In the Pacific Northwest wet conditions in coastal areas will give way to drier conditions in the summer but may return again in the fall, while inland areas may continue to see very dry conditions that will lead to increasing drought and water shortages. The Northeast could see wetter than normal conditions so a drought there this year seems unlikely. The central part of the United States could be the hardest hit by drought conditions and the drought that is already present across a large part of the central and western US is likely to get worse over the next few months with little rain expected. That will affect not only gardeners but the farmers of the main grain-growing area of the US, at a time when Ukraine, normally a big grain producer, is not likely to be able to produce a regular crop this year because of the ongoing war.

Source: Walter Siegmund. http://commons.wikimedia.org/wiki/File:Eschscholzia_californica_7717.JPG

Managing your garden in La Niña

Gardeners in the Southwestern US will have the most difficult conditions to manage this year due to the water restrictions and ongoing drought there. Proper use of irrigation and conserving soil moisture through mulch and appropriate choice of plants are good ways to keep water use lower. This may also be true of gardeners in the central US, where the drought could also be severe this summer. In the Southeast, the summer rain you get will depend on tropical activity and where the storms go so you could see either wet or dry conditions. Managing your garden for both dry periods and potentially heavy rains is a challenge that you may need to deal with this year. In the Northeast, the climate may be easier to contend with this year but even short-term dryness can be a problem for plants that need regular infusions of water. In the Pacific Northwest, predictions for a warmer and drier than usual summer mean you should pay careful attention to water-conserving measures, especially in inland areas where drought is already a problem. If you are outside the US, then make sure you understand how La Niña is likely to affect your region and manage your garden accordingly.

The plants have eyes! Another foray into B(ad) S(cience).

A week or so ago one of my “friends” sent me a link to a new journal article that claims plants can “see.” (The use of quotes here indicates that plant vision is suspect, as is the friend status of the person who sent the article.) Of course, dissecting the claims in this article became an all-consuming task for the next several hours. And rather than writing off those hours as never to be reclaimed, I decided a blog post would at least set those thoughts down to save other skeptics the time.

The article can be found here; it reports on the ability of leaves to mimic other leaves. While the concept of leaf mimicry is not new and has been seen in agricultural weeds for decades, this article goes a step further in claiming that plants can actually see the leaves they are to meant to mimic.

But let’s back up a bit to explore leaf mimicry, which is a thing. Leaf mimicry serves to protect plants against herbivory and other types of removal (like weeding). This phenomenon was reported decades ago where agricultural weeds were shown to change their morphology to more closely resemble the desired crop. The benefit is obvious: if a weed looks like a crop plant, it is unlikely to be removed through hand weeding. Likewise, if a weed resembles a poisonous plant, herbivores that are visual learners will avoid these weeds. When some plants of a species are disproportionately allowed to survive (i.e., not eaten or removed), they reproduce better. Higher reproductive capacity means more offspring: this is the process of natural selection. We can even see this in dandelions in our lawns and gardens.

One astounding leaf mimic is Boquila trifoliolata (a tropical woody vine). This vine can be found on several host trees, where it mimics the leaves of each host and thus avoids herbivory (this short article by Gianoli and Carrasco-Urra is worth reading).

Boquila trifoliolata [courtesy of Wikipedia]

The article I’m currently dissecting doesn’t report on field observations of mimicry; instead, it looks at an indoor situation where B. trifoliolata is grown in the presence of artificial leaves. The authors claim that the leaves on the living vines began to take on the shape of plastic leaves on artificial vines located on a shelf above them. Despite Gianoli and Carrasco-Urra’s earlier speculations that horizontal gene transfer or volatile chemical signals might trigger the mimetic response, these authors propose that plants can see the artificial leaves and adjust their leaf morphology accordingly. They base this hypothesis on papers written over a century ago that suggest plants have ocelli (“little eyes”) as a way of sensing light. Of course, a century ago we were decades away from discovering pigments such as phytochrome and cryptochrome, both of which inform plants about light conditions in their environment.

Figure
Image from White and Yamashita, 2022

There are a lot of problems with this paper; it would take me a separate blog post to critique the Materials and Methods section alone. But the biggest red flag for me was the following paragraph:

This reflects significant author bias: the experiment didn’t work in the winter, so they did it in the spring and summer to see if they got results they liked better. And apparently they did.

SIDEBAR: Other potential red flags that careful readers might note include
*A lead author with no apparent connection to an academic institution
*A journal (Plant Signaling and Behavior) that focuses on the questionable field of “plant neuroscience”
*An experiment performed under vague and uncontrolled conditions
*Typos, grammatical errors, and awkward writing throughout

I’d like to propose a couple of different reasons that these leaves may have changed shape in the summer and not the winter:

  1. Summer months are hotter and brighter than winter months. The experimental leaves were exposed to increasing heat and water loss compared to the shaded control leaves. Newly expanding leaf morphology changes in response to changing environmental conditions.
  2. Under increasingly hot temperatures, plastic releases volatile chemicals, many of which are toxic. Leaf morphology has been demonstrated to change in response to air pollutants.
Leaves can orient themselves vertically to reduce exposure to high light intensities. Morphology can change, too.

This is a deeply flawed article based on a poorly designed experiment and reflects significant author bias in the interpretation of the results.

And just for more cowbell, here is Christopher Walken’s take on plant ocelli.

People and Plants

This is the springtime installment of our random, look-behind-the-scenes of the plant world blog post. In this episode we’ll take a look at William Forsyth, a gud Scottish horticulturist.

William Forsyth 1737-1804

William Forsyth was born in 1737 in Old Meldrum, Aberdeenshire in northeast Scotland. In 1763 he moved to London to work at Syon Park House for the Earl of Northumberland. After that gig he transferred to the Chelsea Physic Garden and trained as a gardener under Phillip Miller. He eventually took over the head gardener position in 1771 and held that post for several years. Forsyth was quite a “plant nerd” who enjoyed exchanging plants with other botanical gardens. He greatly increased the diversity of horticultural collections throughout Britain and Europe with his avid plant trading.

  • In 1779 he was appointed superintendent of the royal gardens at Kensington and St. James’s Palace and held this position until his death.
  • He was one of the original members of the Royal Horticultural Society which held its first meeting on March 7, 1804.
  • Forsyth died on July 25, 1804.

Always a gardener willing to try new things, Forsyth created one of the first known rock gardens in gardening history in 1774 while curator of the Chelsea Physic Garden. He collected over 40 tons of assorted rock from near the Tower of London, included flint and chalk from nearby downlands (an open area of chalk hills) and threw in some pieces of Icelandic lava. Unfortunately the garden didn’t produce as hoped and was considered a failure. Such is gardening.

A pile of rocks does not a rock garden make.

Forsyth published several works on horticulture and was regarded as an expert on fruit tree management and flowering plants. One of his books, Treatise on the Culture and Management of Fruit Trees (1802), was a great success and ran into several editions. You can read it here. His other book, Observations on the Diseases, Defects, and Injuries of Fruit and Forest Trees, was also popular.

Forsyth had a bit of the salesman in his personality…

In 1798 he created a ‘plaister’ which he claimed would heal defects and wounds in trees even “where nothing remained but the bark.” This secret “Composition” as he called it, had a long list of sometimes changing ingredients which included dung, ashes, lime, soapsuds, sand, and urine. Forsyth claimed his Composition could render the timber of poor and derelict oak trees “fit for the Navy as though they had never been injured.”  The Royal Forests were in poor condition at the time and the nation needed sound timber for shipbuilding so as to continue the war with Napoleon Bonaparte.

Forsyth’s directions for making his Composition, in case you’d like to give it a try.


Naturally the Admiralty was very interested in the concoction (my word) and so the Government was persuaded to pay him a large sum of money. The British Parliament gave him a grant of £1,500 ( approximately $260,868.41 in current US dollars) to continue developing his mixture with the understanding the secret formula would eventually be shared with the government.
In the meantime word had gotten out about the Composition and Forsyth decided to take advantage of the situation. He published a best-selling treatise on his ‘plaister’ and the formula was also published in The London Gazette, all for a fee of course. It was too good to last.
A number of prominent British gardeners and botanists experimented with his treatment and quickly revealed (early Garden Professors, show us the science!) that it was quite useless. It didn’t pass the CRAP test. Plus the government took issue with his publishing the formula for the public while having yet to deliver said to the government which had paid a hefty sum for it.
Forsyth was exposed as a fraud. 
But fortunately he died soon after this and his reputation was saved via his publications and lifelong liaising with gardens and gardeners.

I’m sure by now you must have sussed out the plant, right?
If you thought Forsythia, you’re correct!

Khanh Ngo Photography/Getty Images

Forsythia, a genus of spring blooming plants in the olive family Oleaceae and mostly native to Asia and named after William Forsyth.
I can hear you asking, so how is the name Forsythia pronounced? (Yes you are, I can hear you)
In the UK the name is pronounced “For-sigh-thee-a” reflecting the correct pronunciation of Forsyth. In the USA the name is often pronounced “For-sith-ee-a”. Take your pick.


The moral of this story, dear readers, is people have been selling useless garden potions and notions for centuries. So no matter how knowledgable the advice giver seems to be or how may accolades they’ve won, always sift their “Composition” through a sieve of science to screen out the b.s.
(And remember to never apply any sort of manure, literal or figurative, unless advised to by a soil or CRAP test.)

More reading to help you with sifting:
https://www.researchgate.net/publication/315662987_Scientific_literacy_for_the_citizen_scientist_WSU_Extension_Manual_EM100E

Mycorrhizae! Myco what??

You may have heard about these fungi or perhaps not. But if you look carefully on bags of potting mix and on some fertilizers you will see that they are marketed as “essential” to your garden plants.  Claims on mycorrhizal products suggest dramatic growth increases.  These claims like many “snake oil” products can be extreme and are based on science that supposedly bolsters their efficacy.  Mycorrhize are responsible for tremendous growth increased when compared to plants denied access to the fungi.  This has been known for many decades.

Mycorrhizal plant (right) vs non-inoculated plant (left). With permission from Linderman, 2005.

The disconnect between mycorrhizal claims and garden efficacy is that there are usually mycorrhizae present in most gardens. So adding more won’t necessarily improve the growth of plants. There are also some other concerns. Mycorrhizal products are not all the same. Research on product efficacy suggests that about half the retail products available contain no viable inoculum. Spores of mycorrhizae have poor germination viability and do not last long on the shelf although some products contain hyphae as well as spores and these may last longer. So even though products are out there they might not not infect plants.

While mycorrhizal products may or may not hold value for gardeners, mycorrhizal fungi are essential for almost all plants. A few, such as brassicas, do not form mycorrhizal partnerships but all trees, other woody plants and most annuals do become infected by and benefit from these fungi. Plants and mycorrhizal fungi are symbiotic and each receive reciprocal benefits when each partner is well established.

There are two broad categories of mycorrhizal fungi the VA (formerly VAM) or vesicular-arbuscular mycorrhizae and the ectomycorrhizae, (EM). VA mycorrhizae are fungi in the class Zygomycetes related to the common bread mold fungus. They inhabit 80% of the worlds plants. They can not be seen without staining and careful microscopy. Ectomycorrhizae are the other form and they are exclusively from the Basidiomycete or mushroom forming class of fungi. Many of the mushrooms that grow in forests are actually supported by tree roots they affiliate with. Ectomycorrhizae change the shape of roots giving them a stubby appearance. This is because ectomycorrhizae form a mantle around the root of hyphae called the Hartig Net.

Ectomycorrhizae can be seen in soil threading in and around roots often covering them in white mycelium.

So why the big deal? What are the benefits that plants share with mycorrhizae and how do the fungi benefit from their plant hosts? Early studies showed that mycorrhizae make minerals, especially phosphorus, more available to their plant partners. Studies show that mycorrhizae increase the efficiency which plants use many fertilizer elements, even nitrogen. Fungi become “sinks” for plant carbohydrate or sugar. Mycorrhizal hyphae replace root hairs in most infected plants and vastly increase the surface area of roots. This gives roots the ability to withdraw water from very dry soils since mycorrhize can access water held at higher pressures on soil particles than roots can. Thus mycorrhizae infected plants especially with EM, have greater drought tolerance.

Mycorrhizae are an integral part of the carbon cycle on earth and are the reason why there is roughly 2X the amount of carbon stored in soil than in all the plants growing above the soil. This is because up to 20% of plant photosynthate is excreted into soil as a stable polymer called glomalin. Glomalin is responsible for binding soil particles and creating micro-aggregates and soil with water soluble aggregates does all kinds of good stuff. It increases soil moisture holding capacity while improving porosity and drainage. All of this helps reduce root rot hazard.

Mycorrhizae also affiliate with microbes. The hyphae of mycorrhizae cultivate bacteria which produce antibiotics that protect the host plant from pathogens. Linderman coined the term mycorrhizosphere to describe the microbial community that affiliates with these fungi. Plants are also protected by the Hartig net of EM mycorrhizae because it provides a shield or barrier so that pathogens have a difficult time invading the plant root. So, mycorrhizae greatly benefit plants by defending their roots from pathogens.

Amanita muscari is an EM fungus that grows on tree roots

How do we keep the mycorrhizae growing with our garden plants? Most gardens are well inoculated with mycorrhizae at least the AM kinds. To get more access to EM it is necessary to also provide the organic carbon that they affiliate with. While EM absorb sugar from plant roots, their hyphae also grow into woody mulches helping to solubulize the nutrients contained in mulch and bring them back to their tree hosts. The litter and woody debris that fall in forests (litterfall) are essential for these organisms. We can simulate litterfall in gardens by applying fresh arborist chips and nourish the EM fungi as well as our woody garden plants at the same time.

A chip drop of fresh arborist chippings. Coarse woody mulch supplies additional carbon (energy) to soil fungi that benefit our landscape plants. [For a free, peer-reviewed publication on using arborist wood chips, please click here]

References

Corkidi, L., Allen, E.B., Merhaut, D., Allen, M.F., Downer, J., Bohn, J. and Evans, M. 2004. Assessing the infectivity of commercial mycorrhizal inoculants in plant nursery conditions. J. Environmental Horticulture 22:149-154

Corkidi, L. Allen, E.B., Merhaut, D., Allen, M.F., Downer, J., Bohn, J and Evans, M. 2005. Effectiveness of four commercial mycorrhizal inoculants on the growth of Liquidambar styraciflua in plant nursery conditions

Linderman, R.G. 2005. Bio-based strategies for the management of soilborne pathogens. Presented at the Landscape Disease Symposium, University of California, Santa Paula.

Linderman RG. 1988. Mycorrhizal interactions with the rhizosphere microflora: The mycorrhizosphere effect. Phytopathology 78:366-371.

Measuring the weather in your garden

I started writing for The Garden Professors a little over a year ago. My very first posting was on “The weather where you are.” In that article, I described some simple ways to measure the microclimates around your yard using some simple hand instruments. But many of you are already well past that and have your own weather stations. For those of you who don’t, here are some considerations for adding a weather station to your garden and a shameless plug for CoCoRaHS (Community Collaborative Rain Hail and Snow Network), a citizen science network of rainfall (and snowfall!) observers around the United States and Canada as well as a few additional stations in Mexico and the Bahamas. I am the current state CoCoRaHS coordinator for Georgia and we are in the last week of the March Madness competition to sign up new observers that they have every year. Even though this year’s competition ends on March 31 you can sign up and contribute to the precipitation record for your state any time. They have links to purchase their required rain gauge on their website on the bottom right side. They also have a very useful guide for Master Gardeners. If you are not in the United States or neighboring countries, you may be able to find rainfall observing networks in your country that you can join as well.

CoCoRaHS rain gauge. Source: NASA.

Equipment that is used to measure the weather at a location can vary from a very simple thermometer and rain gauge that you can buy at a hardware store to a sophisticated piece of equipment holding multiple sensors that costs thousands of dollars. The research-grade Campbell Scientific stations that we use in the University of Georgia Weather Network cost about $12,000 each, which is well out of reach of most homeowners, but there are plenty of options for weather enthusiasts that are much more reasonable in price.

University of Georgia weather station in Blue Ridge, GA, at Mercier Orchards. Photo: Eddie Edenfield.

A basic weather station may just measure a few variables like temperature and pressure but most people like to add additional sensors like humidity, precipitation, and wind speed and direction. If you are even more ambitious, you might add solar radiation, soil temperature and moisture, and more specialized sensors like leaf wetness. Weather Underground has a useful list of personal weather stations with some details about what sensors each one has, although you will have to click through the links to get pricing. Weather Underground also provides information on how to hook up some of these stations to the web so that you can share your weather information with others and contribute to their own citizen science network.

The single most important factor in getting useful information from your weather station is putting it in a good location. The weather station should be sited where there is good air flow so that you get a representative temperature and humidity for the area. The temperature sensor should also be shaded so that it does not warm up due to direct sunlight. Many stations include an enclosure to shield the thermometer from the sun’s energy. The enclosures are usually white to reflect sunlight and have louvers to let air flow through the enclosure. Some use fans to increase the ventilation of the temperature sensor, especially when winds are light.

Rainfall measurements also require good siting. Precipitation gauges should be placed where they will not feel the effects of any nearby trees or buildings. Usually you need a cone of 45 degrees wide above the top of your rain gauge that does not have any blockage from trees or buildings. Even that may not be enough in all conditions. My own rain gauge is located to the west of my house because that is the only open spot in my tree-filled yard and I notice that in storm systems with wind from the east, the rainfall is lower than other nearby stations because the building is blocking the wind and keeps some of the rain from falling into the gauge. Obviously, you don’t want any moisture from trees, wires, eaves, or fenceposts dripping into the gauge, so look around before you settle on a spot. Dr. Peggy LeMone from the National Center for Atmospheric Research in Colorado described her struggles with making accurate rainfall measurements and why siting is important after a big rain event in 2013.

Rain gauges at Eskdalemuir, Scotland, at the British Geological Survey Magnetic Observatory. The gauges are in pits to cut down on wind effects on the top of the rain gauges.

Rain gauges come in a variety of types. The simplest is a can or tube with vertical walls that you can use to catch rain and measure it at regular intervals (usually once a day at the same time each day for consistency). The CoCoRaHS gauge is a 4-inch diameter plastic tube with a funnel and an inner and outer cylinder that can be easily read to 0.01 inches. It holds up to 11 inches in all, and in some big rain events, it might need to be emptied several times in a day! Many personal weather stations use a tipping bucket rain gauge that has an opening with a funnel that drips the water into a bucket that has two sides on a pivot point. The National Weather Service uses weighing rain gauges to calculate the depth of precipitation based on the weight of the water inside the gauge. The Weather Makers has a good description of how these three types of gauges work as well as illustrations about what they look like. Other newer types of rain gauges include optical gauges that use a photoelectric eye to count water droplets as they pass through a funnel past a light source and haptic gauges that use the sound of raindrops hitting a surface to estimate how much rain has fallen based on the raindrop impacts.

Wind sensors should also be placed in an open area with no blockages from trees or buildings nearby. Putting them on top of a roof might seem like a good idea, but the wind flow over the roof can divert the air and speed it up, so that is generally not a good place to put them, although they are certainly very decorative. Some wind sensors have separate instruments for measuring the speed and direction of the wind while others use a combined sensor that can do both at once.

Wind vane on the top of King’s Cross Station in London, England.

If you love the weather and want to know more about what is happening in your yard or garden, adding a weather station can provide you with entertainment as well as information that can be helpful to track the climate conditions in your garden such as when frost occurs and how much rain you got so you can water appropriately. It also provides a great place to compare conditions with the other gardeners in your area—you might be surprised at how measurements change from one neighborhood to the next!

Shopping for landscape plants – an illustrated cautionary tale

Flower shows, like this one in Philadelphia, get gardeners excited about buying new plants.

“In the Spring a gardener’s fancy lightly turns to thoughts of…plant shopping!”

If Alfred, Lord Tennyson had been an avid gardener, I am sure he would have included the above line in his poem “Locksley Hall.” I certainly look forward to visiting nurseries and plant centers in the spring to see what new goodies await. But my enthusiasm is tempered with caution – because bad things can lurk in otherwise perfect plants. I posted a four-part series way back in 2009 (the first year of our blog) on inspecting nursery plants.

I strongly recommend you review these posts before you buy – they are 13 years old but the information is still 100% valid.

Part 1: inspecting the root flare and trunk.

Part 2: inspecting the roots.

Part 3: avoiding suckers.

Part 4: avoiding poorly pruned young trees.

Today’s post will add some new nursery nightmares to avoid at all costs.

Free complementary gift!

Make sure you’re buying a cultivar and not a nutrient deficiency

It may be striking, but it’s not healthy.

There are lots of interesting cultivars out there with unusual foliage. This dogwood is not one of them. Interveinal chlororis is a symptom of foliar nutrient deficiency – either iron or manganese – most likely caused by excessive phosphate fertilizer.

Fusion

It’s two…two…two trees in one!

Fusion can be innovative in music and cuisine. Not so much in plants.

You can’t say they didn’t warn you

Back to nature

The scion of grafted plants is rarely as vigorous as the rootstock. Usually you have to wait a few years for the rootstock to take over, but there’s no waiting with these weeping silver birch specimens! But given how hideously trained these trees are, maybe it’s better that they will be slowly subsumed.

Just don’t do it. Please.

Agua Es La Vida.

No swimming? That’s the last thing we should be concerned about.

Water is a precious resource and gardeners are often careless with it. Water rationing is a real thing for many of us and, with continuing and spreading drought, may become a reality for many more. Is it possible to have a beautiful garden while minimizing water use?
It is indeed.
[Disclaimer: This blog post is about ornamental landscapes. While efficient water use is also needed for a production garden, the need to produce food is the priority.]

Lovely!

Choose Waterwise Plants
This might seem like a no-brainer but it deserves consideration. As we develop, add to, or change our landscapes we should choose plants that, once they’re established, will thrive without needing additional irrigation. And don’t fall into the “native plants are more water use efficient” trap. Growing any plant outside of its original environment, or planting it in urban or compromised soils in a micro-climate it’s not adapted to, and guess what – native plants can be water hogs too. Carefully considered non-native, regionally adapted plants can use less water once they’re established, provide a healthy environment for wildlife and give you a lovely garden.

Check plant tags for water use information.

Group Plants According To Water Needs
This is the only instance I can think of when “companion planting” is a description that works. Group plants with similar water requirements together. And by “together” I mean in a same hydro-zone. If possible, don’t mix plants with different water needs in the same planting bed. Here’s a local example I see quite often: oleander is a popular plant in my area but it needs extra water to be truly happy while Leucophyllum is also a popular plant but needs very little to no extra water once it’s established. A popular landscape combo is oleander as the backdrop with Leucophyllum in the foreground, yet they’re all in the same water zone. So to keep the oleander happy more water must be used but that overwaters the Leucophyllum. And you can imagine the reverse for yourself. In this case, opposites don’t attract.
If you use an automatic system adjust the zones to optimize each plant groups water use. Add, resize, remove emitters or feed lines to help you accomplish this. It’s not a “one size fits all” thing.

Group plants with similar water needs. This photo is an example of how not to plant. The opuntia is well watered, almost too well, yet the petunias in the foreground and the agave in the back left are water stressed.Not going to discuss the “pruning” of the sotol and agave. Nope, not going there.

Monitor Soil Moisture Depth With A Simple Soil Probe
Whether you use an automatic irrigation system, water manually, or depend on the weather, monitoring soil moisture depth should be a part of your garden maintenance routine. We’ve already talked about this in a previous GP blog post so I won’t go into it more here. Just consider this a friendly reminder to make it a part of your gardening routine.

Soil moisture probes, easy to make or purchase.

Watch The Weather
Keep an eye on the weather forecast and turn off automatic systems as needed. You can install a rain sensor or “weather eye” on the system but don’t expect it to always work correctly, or at all. You’ll still need to monitor the situation.
And don’t assume just because it rained your landscape received adequate water. Check the soil moisture depth to be sure. If you have containerized plants on your automatic water system you should check their soil moisture levels too. They may not have received enough moisture from that rain storm that watered the rest of your landscape.

We’re sprinkling in the rain, just sprinkling in the rain…


Closing Thoughts: Do you really need that automatic irrigation system?
Yes it’s convenient, but is it necessary?
Warning- Anecdotal observation!: After ~20 years of being an Extension Master Gardener and Master Naturalist, working outreach events and phone help lines I’m convinced that automatic watering systems waste more water than they save.
There, I said it.

Sprinkler overspray, there’s no excuse for this.

It’s not the fault of the system – it just does what the controller tells it to do. Incorrect installation or placement of feed line/emitters, lack of maintenance, using the wrong emitters for the situation, sloppy programming, and running the system when it’s no longer needed all result in water wastage. An automatic irrigation system is not an install, set and forget thing but it’s usually treated as one. Our goal as gardeners should be to have a landscape that is not dependent on continuous supplemental irrigation. We should lead by example.
If you must depend on an automatic system be sure it’s in good repair, the emitters are the correct type, size and properly placed for the situation and you’ve programmed the controller correctly. Adjust the system as plants grow and mature, this is especially important for trees. Move and add emitters as the canopy and trunk diameter expands.

Notice the loose bark on the right side of the trunk. There are similar patches on the other side as well. This tree is in trouble.
This tree is starting to leaf out but you can estimate the canopy spread.
And here is its one water source.
Another view and yes, that is solid sheet plastic you see there.
Poor tree.

Aqua Es La vida“…”Water Is Life.”
Let’s make every effort to use it wisely and conserve it in all aspects of our lives. Like the song says, “…Don’t it always seem to go that you don’t know what you’ve got ’til it’s gone…”
And by then it’s too late.

More info on efficient water use here:
https://aggie-horticulture.tamu.edu/earthkind/drought/efficient-use-of-water-in-the-garden-and-landscape/

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=12962

This is a great handout!
https://cals.arizona.edu/extension/ornamentalhort/waterquality/watering_trees.pdf

https://ucanr.edu/sites/UrbanHort/Water_Use_of_Turfgrass_and_Landscape_Plant_Materials/Estimating_Water_Requirements_of_Landscape_Trees/

https://www.epa.gov/watersense/watering-tips

https://www.energy.gov/sites/prod/files/2013/10/f3/est_unmetered_landscape_wtr.pdf


The ABC’s of Plants for Bees!

A yellow flower with a pollen-covered bee resting on top.

A bee collecting pollen from a Black-eyed Susan (Rudbeckia hirta).

Though it might not seem like it for some of us who are still in the throes of winter and it especially feels like a distant dream as I look outside my window here in Montana, but Spring is right around the corner. Along with this magnificent season filled with new life in our gardens and landscapes our world will soon be buzzing with pollinators as well!

Most gardeners have a basic appreciation for pollinators. We know they are responsible for many things including providing important agricultural and economic services by pollinating many of the crops that we eat and by maintaining the diversity of plant communities (which help feed and house lots of other wildlife who share our space). Although lots of animals are pollinators, including birds, flies, beetles, butterflies, bats, small rodents, and more, bees are the most important of them all! This is because they have branched hairs covering their body which make them extremely efficient at carrying pollen from plant to plant.

Honey bees often get most of the publicity when you think about pollinators, or bees in general. Although they are really important to our agricultural operations they are not native but were brought to North America by colonists in the early 1600s. Some gardeners can even name a few additional types of bees but many may not realize the impressive number of bee species that are native to North America, estimated to be around 4000!

We are also becoming more aware of the fact that many wild and domesticated bees around the world have been undergoing declines over the past few decades of observation- which brings up questions about what we can do to help. The cool thing about this is that we, as gardeners, can have a positive impact on our bees, by thinking about them intentionally as we design and plant our gardens and take care of them throughout the year.

Just like us, bees need a few basic things to survive. They need food, a place to live, and protection from practices that can harm them (such as improper/unnecessary pesticide use). Each of these needs can be an entire blog post of its own, and in fact might be in the coming months, but my goal for this specific post is to introduce you to some of the resources that have regional information for selecting plants for pollinators.

Pink flowers with a large bee collecting nectar from them.

A bumble bee sipping nectar from a ‘Pink Spire’ Summersweet (Clethra alnifolia).

Pollinator Partnership, Xerces Society, National Audubon Society and lots of other educational organizations have a vast array of plant lists available for the pollinator enthusiast (see the resources linked at the end of this post to find an appropriate list of hardy plants adapted to your region). As you select your favorites from these lists there are a few things you should keep in mind to ensure you have the best impact on bees with the plants you select:

  • Add a mixture of different colors, textures, and sizes of flowering plants to attract the largest diversity of bees. Some bees (like long-horned bees, leafcutter bees, and honey bees) are generalists, which means that they will forage on a variety of different flowers. Others (like squash bees and sunflower bees) are specialists, which means that they will usually stick to plants in certain families, genera, and even species. By incorporating a diversity of plants in your pollinator garden, you can also accommodate a larger diversity of bee species!
  • We know that native plants are an awesome addition to pollinator gardens (because they are well-adapted, and evolved with the native pollinators of the region). That being said, you don’t have to avoid non-native plants altogether. Recent studies show that native and non-native plantings can have a lot of overlap in pollinators. In addition, non-native and native plants will also attract different types of pollinators so you can mix it up!
  • Make sure there are flowers throughout the growing season by planting things that will be blooming while bees are continuing to forage. Certain bees are active during certain times of the year when they are collecting pollen and nectar for their nests. Having something flowering throughout the year means that a variety of bees can take advantage of these floral resources. Some of the most critical plants that you can select are those that bloom early and those that continue to flower into the fall as the growing season ends. These early and late season flowers are very important because there are fewer resources available for pollinators during the times that bees are getting started (in the early months of spring) and when certain bee species are getting ready to overwinter in the fall. Having these early and late season flowers means that bees will have a source of food throughout the growing season, not to mention the beautiful blooms that you’ll get to enjoy throughout the year.
  • Stay away from plants that don’t have nectar/pollen sources (like some modern hybridized flowers) or those that have complicated features (such as double petals) which make it difficult for bees to actually get to the nectar source.
  • Keep these plants safe for pollinators, don’t spray pesticides on plants that are flowering. Or you can wait until the blooms have gone.

Now, you get to enjoy the fun part of choosing plants that are going to add beauty and benefit for pollinators in your yards and gardens.

Large pink flowers, with a bee resting on the side of the petals. Cactus spines in the background.

A bee resting on a Prickly Pear Cactus flower (Opuntia spp.).

Stay tuned for future posts about pollinators and other beneficial insects in the coming months. If you have questions about specific plants, their suitability or pollinators in general, visit the resources below or contact your local Extension Offices for more information.

Resources:

Pollinator Partnership Planting Guides:
https://www.pollinator.org/guides

Xerces Society Plant Lists:
https://xerces.org/pollinator-conservation/pollinator-friendly-plant-lists

Audubon Society Plant Database:
https://www.audubon.org/native-plants

(Some) Fact Sheets about Gardening for Native Bees:

Seitz, N., vanEngelsdorp, D., & Leonhardt, S. D. (2020). Are native and non‐native pollinator friendly plants equally valuable for native wild bee communities?. Ecology and evolution10(23), 12838-12850. https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.6826