The Garden Professors™

Is it spring yet where you are? How can you tell? Here in the Southeast, we are well along the path to spring, even though the calendar says we are still in winter. I can tell by the daffodils, spring peepers, and migrating birds I see overhead. I know those of you farther north may not be seeing any signs of spring yet, with winter storms still moving through your states and lots of snow on the ground as well as frigid temperatures, but trust me, it is coming!

What is phenology?

I first heard the description of the onset of spring as the “green wave” in “The American Seasons”, a book by naturalist Edwin Way Teale. It refers to the northward movement of the appearance of the first green leaf on bushes and trees as warmer temperatures move north and the days get longer. I find it to be a very imaginative and effective way of visualizing how spring moves from south to north (in the Northern Hemisphere) over the course of the season. Phenology is the study of when specific biological and natural events occur, such as seeing the first green leaf of the year, watching your forsythia bloom, seeing your local lake freeze over, seeing sandhill cranes fly north on their annual migration, or watching your favorite tree reach peak color in fall. Many of you probably keep track of these occurrences in your own gardens and use them to compare the climate from one year to the next. But did you know that there is a whole group of dedicated observers who have done this over long time periods and recorded their data for others to see and use?

The National Phenological Network (NPN) is a group of dedicated citizen scientists and others who keep track of the yearly occurrence of when different indicators occur and report them to the NPN. Maybe some of you are part of this network!  They have an excellent database on their website with information for many different species of plants and birds as well as other interesting phenomena. You can explore it in a number of different ways, including through time series and maps. It helps to know the Latin names for the species you are interested in because different species respond differently to the weather! I even used it a couple of weeks ago to help a film director determine how long he had to shoot a Christmas movie before the trees leafed out in Georgia (response: do it soon!).

Where is the green wave now?

One section of the NPN site shows the 2022 movement of the green wave north with time and how it compares to the long-term average conditions. This week’s map is shown below, with areas later than average highlighted in blue and areas that are earlier than average in red. You can see that while southern Florida was ahead of normal, the green wave slowed up quite a bit later in January and early February as colder temperatures covered a lot of the region. That has switched more recently, with warm temperatures across the southern Plains showing the green wave reaching there about four days earlier than usual. Spring is also early coming to large parts of the West Coast, which is currently experiencing much warmer than normal conditions in most areas. If your area is not colored yet, you are still in the depths of winter, but keep watching and spring will (I hope!) be coming soon. I don’t know of a similar product in other parts of the world, but if any of you know, please share the information in the comments.

What do phenological records tell us about climate change?

While our local records in the United States are only a couple of hundred years old at most, other parts of the world have much longer records. Last year, Japanese scientists released a graph showing the change in the peak bloom date of cherry trees in Kyoto, Japan, for the year 800 to the present. While there are a lot of ups and downs over time, the trend towards an earlier peak bloom in more recent years is unmistakable. Since 1912, the average peak bloom date for the cherry trees in Washington, DC, has also shifted forward from April 5 to March 31. Other records showing the warming of the world include migration patterns of birds, pollen counts from trees, and ice-off dates on lakes in colder areas. Glacial ice and sediment cores from lakes and the ocean can provide timelines of how local biological systems have changed over time periods going back thousands of years. Many scientists are worried about the long-term consequences of these changes since not all species are migrating at the same rate and so some animals, birds, and insects may outrun their main sources of food if they move north faster than the plants that feed them.

Phenological records are important for monitoring long-term climate change because the records go back in time much farther than instrumental weather records do. Even though blooms and leaves on plants respond to temperature and sunlight in a non-linear way because they integrate all of the influences into one observed piece of data, they can still provide very useful information about how the environment is changing over time. A really interesting related use of this information was described recently in a story showing that the meteor that ended the Cretaceous period 66 million years ago probably occurred in spring due to the remains of fish that died in the devastating massive waves in the Gulf of Mexico that occurred after the meteor hit. Scientists assumed that the fish died immediately following the impact, and used their bones to determine that the fish were early in their annual growing cycle. Similar work has used buried vegetation to trace past tsunamis in coastal areas that may have been linked to other asteroid impacts or earthquakes that occurred before history was written down.

Wherever you are, I hope you enjoy watching the change in the seasons and in the world around you as much as I do. In spring, every day is a new adventure in seeing what is changing and hoping for the summer to come. I encourage you to keep a diary or other record of what changes are occurring in your garden so that you can see for yourself how the climate is changing from year to year.

Ukraine is all in the news these days as Russian troops are amassed along its borders in Belarus and neighboring Russia. I have some knowledge of Ukraine having visited the Chernobyl nuclear exclusion zone (the “Zone”) four times in 2012, -15, -16 and 2018. I had planned more visits but the global COVID-19 pandemic prevented my return to Ukraine and the Zone. The accident at Chernobyl was the worst nuclear accident in the history of mankind releasing more radio isotopes than the event at Fukashima and had long ranging impact on Ukraine and the then Soviet Union. Some say that the event precipitated the down fall of the former Soviet empire.

Today the Chernobyl Nuclear Power Plant (CNPP) remains one of the most radioactive places that you can safely visit in the world. It was also the source of most of the world’s background radioactivity. When the disaster occurred in 1986, it temporarily raised the background gamma radiation of the entire planet by two percent. This rapidly declined as the half life of the released gases is very short and their radioactivity went away a few days and months later. Some of the elements, like radio Cesium 137 and Strontium 90, have longer half lives (around 30 years) and there was enough of them released to maintain high levels or gamma radiation where the fallout was most concentrated around the power plant. Elements such as plutonium remain radioactive for thousands of years but the amount of plutonium released was much less than that of strontium or cesium. Today the background gamma radiation near the CNPP remains up to ten times greater than the normal background levels found in the Ukraine capitol of Kiev. So how has this affected the gardens of Pripyat, the workers town not less than a km from the CNPP? To get to that let’s first talk more about the worker’s town and the disaster and then move on to what happened to the horticulture years later.

When the reactor exploded in 1986 (and yes it actually exploded) the area was surrounded with an exclusion zone complete with military checkpoints at 10 and 30 km circles away from the CNPP. This was an effort to keep people away from the radiation. The town that held the CNPP workers is Pripyat. It was a modern city of about 50,000 residents. It was considered the model city of its day as Chernobyl was considered the pinnacle of energy producing technology. Pripyat had a performing arts center, sports stadium, nightclubs, libraries several schools, public pool, and an amusement park. The entire population of the town was evacuated by bus in April 1986 in a few days. Although they were told they would return, most never did. Prypiat fell into ghost town status and remains that way to the present day, and like most ghost towns it was heavily looted. Some recent reports suggest that the Ukraine military has been knocking down buildings recently. Like any well planned city, Prypiat had an urban forest plan, street trees on every avenue and boulevard and gardens with ornamental plants. All were abandoned in 1986 and left to rainfall, radiation and the animals that remain there today.

The forest returned vigorously to Pripyat and animals roam the streets. The ecosystem recovery in the Zone has been dramatic over thirty years. Remnant street tree populations remain along the avenues but many more wild and non native exotics have invaded the spaces. The once athletic stadium playing field is now a small forest.

The forest encroachment has had a devastating impact on the architecture of the remnant buildings. Trees grow everywhere and when they attack the buildings they are able to collapse the floors and walls effectively demolishing the structure.

People have great impacts on the health and structure of trees. When left alone they develop their own natural structure according to their genetic code. Over several visits we measured growth of trees in the Zone and took pictures to analyze their structure. We found that trees of similar age growing in Pripyat were smaller in size but had better branch structure due to LACK of pruning for 30 years.

It is hard to imagine what the gardens of Pripyat looked like at the time they were in cultivation because we have so few records of the city to review. There are the remnant street trees which my friend Igor Lacan studied extensively. Garden plant remnants are mostly gone except for extant rose bushes which can still be found around the city.

It is hard to know what the gardens could have become before the forest invaded the city. We can look at landscapes in Kiev that exist today and see the overall gestalt of Ukraine gardens. They are kind of wild not meticulously maintained in public spaces but they also have charm, character and beauty.

As Ukraine is on the brink of uncertainty there are a few things that are certain, the radiation in the Chernobyl nuclear exclusion zone will continue, people will likely not be allowed to travel freely there, and the trees will continue to grow. The fate of gardens and trees in the capitol city of Kiev is less certain.

References:

Lacan, I., J.R. McBride, and D. De Witt. 2015. Urban forest condition and succession in the abandoned city of Pripyat, near Chernobyl, Ukraine. Urban Forestry & Urban Greening 14.4:1068-1078.

Burlakova, E.B. and V.I. Naydich (eds). 2012. The Lessons of Chernobyl: 25 Years Later. Nova Science Publishers, N.Y.

Downer, A.J. and J.F. Karlik. 2019. “A Comparison of Two Horsechestnut Street Tree Plantings in Kiev and Pripyat, Ukraine.” Open J. Forestry 9: 255-263.

Karlik, J.F. and A.J. Downer. 2019. Comparison of Gamma Ray Dosimeters in a Field Study in the Chernobyl Exclusion Zone. J. of Air and Waste Man. 11:1361-1367

…National Pesticide Safety Month. Let’s review some key points of safe pesticide use. 

Socrates said, “ The beginning of wisdom is the definition of terms”

So let’s define a pesticide.
A simple definition is any substance used to control, deter, incapacitate, kill, or otherwise discourage organisms harmful to plants, animals or humans can be classified as a pesticide. A fuller definition can be found here. Germane to our discussion, herbicides make up 80% of all pesticide use. As gardeners we should know how to properly handle any chemicals we choose to use.

Anytime you use a pesticide, be sure to read and follow label instructions. The label will include important information for protecting yourself and it will tell you how to apply the product in the way that it will work best. Be certain the pesticide you’re using is correct for the job.

All pesticides carry labels which provide varying levels of information including the signal words “Danger”, “Warning’ or “Caution”. These signal words have specific meanings in relation to the pesticide. Products labeled “Caution” are the least toxic, “Danger” are the most. More information on signal words can be found here.

Correct and controlled application is responsible pesticide use. While some pesticides can be broadcast, e.g., pre-emergents and some lawn grub control products, most of them need to be precisely applied. Use correctly calibrated equipment recommended by the label directions and apply precisely. Avoid overspraying and watch out for drift.

And finally, wear protective clothing and use the correct application method and equipment as stated on the label. Always keep children and pets away while you’re applying any product. Observe wait times before allowing people or pets back into or onto treated areas. When you’ve finished application wash your hands, face and any skin that’s been exposed to the product. If needed, launder protective clothing separately from other clothing. 

For more information:
https://www.epa.gov/safepestcontrol
http://npic.orst.edu

If you have watched the news at all in the last two weeks, you know that there was a huge underwater volcanic eruption near Tonga in the South Pacific Ocean on January 15, 2022, that spewed ash and gases into the atmosphere. It blew with such force that the sound of the eruption was heard in Alaska thousands of miles away and the atmospheric pressure wave it set off has traveled around the earth as many as ten times according to satellite and ground-based sensors. With such a large signal, you might wonder what impact the eruption could have on our weather and climate for the next year. In this post, we will explore how volcanoes in general can affect the climate around the world and whether the Tonga eruption is likely to change our gardens’ climate this year.

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What do volcanic eruptions emit into the atmosphere?

When volcanoes erupt they put out both ash and gases. The ash is made of tiny particles of rocky material from solidified lava and sometimes pieces of the volcano destroyed by the eruption. These particles are carried downwind in a direction determined by the winds at the heights to which the ash can rise. In a long eruption, the plume of ash can blow in a different direction each day, covering the ground when it falls back to earth. Usually ash does not rise very high in the atmosphere because it is quite heavy and so most of it falls out in just a few days.

Volcanoes also emit gases as they erupt. About 99 percent of all emissions are water vapor, carbon dioxide, and sulfur dioxide, with some trace amounts of hydrogen sulfide, carbon monoxide, and other minor gases. The gases are lighter than ash and so they can get lofted much higher up into the atmosphere than ash can. Because water vapor and carbon dioxide are greenhouse gases volcanic eruptions are often blamed for the recent rise in carbon dioxide in the atmosphere instead of human causes. A careful analysis of the relative amounts of carbon dioxide from the two sources easily shows that volcanic activity only contributes in a small way to greenhouse warming compared to fossil fuel burning and land-use changes. But the gases emitted do have a short-term effect on climate that can last several years in the largest tropical eruptions.

What causes volcanic cooling?

Volcanic cooling of the climate is due mainly to the effects of sulfur dioxide and water vapor. As the gases rise, the water vapor condenses and joins with the sulfur dioxide to form tiny droplets of sulfuric acid that can rise to 50,000 feet or more, higher than most commercial jets fly. Those droplets are as shiny as the glass beads they use in stop-sign paint to make the signs reflective, and the droplets have the same effect on incoming sunlight. When they reflect sunlight back to space before it can reach the earth’s surface it reduces the energy we receive at the ground, and the earth gets cooler until those droplets fall out of the atmosphere. Because of their height and small size, that can take several years.

How does the cooling affect global climate?

We know that when you have a large volcanic eruption emitting a lot of sulfur dioxide, especially if it happens in the tropics where the sunlight is most direct, you can see cooling around the globe for the next 2-7 years depending on how much gas the eruption puts out. In the worst case, an eruption like Mount Tambora in 1815 in present-day Indonesia (along with some other eruptions around the same time) resulted in the “Year Without a Summer” in 1816. In the United States, frost was observed every month of the year in New England and eastern Canada, resulting in the loss of many crops. Even the crops that survived had low yields and poor quality that resulted in dramatic increases in food prices. Europe also saw very cold temperatures that resulted in food shortages there.

Other more recent eruptions have also had some impact on global climate, although none was as severe as the Tambora eruption. The most recent large eruption that affected global climate occurred in 1991 with the eruption of Philippine volcano Mount Pinatubo. As the volcanic emissions spread around the globe, the earth’s annual temperature dropped by almost 1 degree F in the years 1991–1993. Sunsets were also spectacular with the scattering of sunlight from the aerosols high in the atmosphere. Some scientists think painters like J. M. W. Turner were inspired by the spectacular sunsets that occurred after volcanic eruptions in the 1800’s.

Will the Tonga eruption affect the climate in our gardens in the next few years?

Since this is a blog for gardeners, you might want to know if the recent eruption will affect the climate in the same way that other eruptions like Tambora and Pinatubo did. If it is going to be much colder than average, then that could affect what you plant in your garden, especially if the plants you want to use are sensitive to frost. Or it could tell you that you might want to hold off on planting those tomato seedlings a little later than usual in spring. In this case, the amount of sulfur put out by the Tonga volcano was only about 60 kilotons compared to 20,000 for Pinatubo, so any cooling effects from the most recent eruption are so small that we will not be able to observe them. Gardeners can breathe a sign of relief this time! But when the next big eruption occurs, the climate may temporarily cool for a few years before it starts to warm again under the impacts of the “human volcano” emitting many more gases and pollutants than natural volcanoes into the atmosphere.

I love plants! I love gardens! I love nature! So why not bring it all inside the house? Who can resist those beautiful Calatheas (Prayer Plants) they sell at Home Depot? House plants afford us the opportunity to garden indoors when it’s hostile outside and they beautify a room like nothing else. There is an incredible selection of tropical, subtropical and succulent plants that we can cultivate indoors. Unfortunately house plants fade…waaa (sad). They lose leaves, they endure pests, they wilt, eventually they die. I am sure this is not the intended outcome when we purchased the beautiful plant in its six inch pot. However, since there are more to be had we can dispose of the tired ones and just buy more fresh ones. For lots of people, house plants are like cut flowers. Throw them away when they fade, especially true for orchids. This does not need to be the case if you understand the basic needs of container culture.

Wise Choices Make Good House Plants

Not every plant you see in the nursery or box store is right for your location. Many tropical plants are grown in greenhouses under high humidity and carefully filtered water. For some plants like the previously mentioned prayer plants, this is a mimic of their natural growing conditions, moist, warm and humid. Many homes may have the warm part but not the humid. Heating systems often dry the air and increase the amount of water drawn from indoor plants. This can be damaging. Unfortunately, placing your plants on a tray of gravel filled with water will not cut it. Adding a humidifier in your plant room may be a solution if you are growing humidity loving plants, e.g., ferns, many orchids, Pipers, Philodendrons, Peperomias, Begonias etc. Another way around this is to cultivate humidity loving plants in terrariums (see blog on terrariums). If enough tolerant plants are grown in a room they will also increase the humidity in the room through transpiration. So add more plants! Always a good idea right?

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Do some research on the house plant you want to purchase before you bring it home to find out where it grows in nature. This will give you hints on its needs. Also know when not to buy a plant, some are just too touchy without controlled environments. If you are new to house plants start off with the easy ones (Pothos, Syngonium, African violets and some Begonias). As you gain confidence move to more difficult or interesting types.

Realize How Plants Are Produced

When you purchase a new plant it is already an old plant, production wise. The grower had a target size or bloom requirement and once the plant has achieved that it is sent out to the retail market. Often a plant has consumed its nutrient charge in the medium it may have filled that medium with roots and the medium may have begun the process of breaking down.

It is good to get plants as fresh from the grower as possible because once they enter the box store or even nursery or plant shoppe, they begin to be affected by the stress of being outside their cultivated environment. Retailers may skip irrigating or keep plants too wet, the air may be dry and the light levels not adequate to sustain growth. The longer plants are in poor growing conditions, the less able you will be to keep them going. Even when your plants look good they may be suffering already and need several things from you such as a soaking irrigation with pure water, fertilization, light, and new media.

First Things First: Repot

Remove your new toy from its container and inspect the roots. They should look white and healthy and should be throughout the medium. If they do not look this way take the plant back. Do not introduced diseased plants to your plant collection. Assuming everything looks good find a suitable container that has drain holes (very important: never use containers w/o drainage holes) larger than the one your plant came home in. Add container medium that you know grows plants well for you or make your own medium from known ingredients. Make sure your medium has a nutrient charge like a slow release coated fertilizer or add small amounts whenever you water your plants.

Next: Irrigate

Growers cultivate amazing house plants because they carefully control the purity of the water they irrigate with by using reverse osmosis filtration. Then they add back the nutrients the plants will need. Harmful salts like sodium, chloride, fluoride, and others are excluded or kept very low in concentration. After your plant is repotted saturate the soil with either distilled water or reverse osmosis purified water. Take careful note of how heavy the container is after irrigation and after all excess water has left the container. This is the weight of a just watered plant. As the plant dries out it will get lighter, simply pick up the plant to tell how dry it is. This is an art that works with smaller containers as well. You don’t have to get your fingers dirty to assess growing medium moisture. On large containers you can tip them to tell how heavy they are. You can also use moisture meters but they are often very inaccurate and will give variable results depending on the level of fertilizer salts in the medium. A last resort is to stick your finger in the pot. Very picky plants like the prayer plant are sensitive to salts in water and excess fertilizer, they will do best with distilled water with a very small amount of soluble fertilizer added back (1/8 of the recommended amount). In some areas tap water is very low salinity and grows good plants, in others it needs reverse osmosis filtration or buy it from the store.

Finally: Location

Now that your new plant is settled in its container, its time to place it in a location where it will get adequate light. Some plants are from dark areas of the forest floor (ferns, begonia etc) and do best with north window light. Others require strong window light (Ficus, many bromeliads, and some succulents). It is also possible to grow plants under lights such as LED’s with great success. This is where your research into plant origins will be helpful. Try to irrigate with high quality water and dilute fertilizer when the plant’s media begins to lighten.

A Note About Pests

As your collection grows there is no doubt that pests may become a problem. They come in on new acquisitions or seem to appear on their own without explanation. Many times new plants are quarantined before joining others. In any case it is best to watch for the common culprits of scale, mealy bugs, and occasionally aphids. If pests are detected there are many remedies available at nurseries. Make sure you identify your pest (Cooperative Extension offices can help) and that the pest is on the label of any product you chose to control it with. Take your plant outside to treat it and let the spray dry before bringing it back in. Quarantine treated plants away from others until you are sure the pest is controlled. Always follow pesticide label instructions precisely. Monitoring for pests can catch an infestation before it gets bad.

Simply paying attention to your plants, occasionally slipping off the container to look at the roots, re-potting when needed and keeping the fertility levels up will ensure good growth and performance. At some point you can move on to propagation of your favorites.

Reference

Faber, B., J. Downer and L.Yates. 1993. Inexpensive, hand-held moisture meters. HortTechnology 3:195-196

In this People and Plants blog post we’re taking a look at the German botanist Adam Lonicer.

Adam Lonicer, also known as Lonitzer, Lonicerum, Lonicerus, or Loniceri, was born on October 10, 1528 in Marburg, Germany. He studied in Marburg and Mainz before becoming professor of mathematics at the Lutheran University of Marburg. In 1554 he received his medical degree and he later pursued a medical career as the city physician of Frankfurt. His true interest though was herbs and the study of botany. In 1554 he married Magdalena Egenolph and worked as a proofreader for his father-in-law, a German printer who specialized in producing herbals.

Lonicer soon decided to produce an herbal of his own, the Kreuterbuch, published in 1546. As the original full title makes clear, Naturalis historiae opus novum : in quo tractatur de natura et viribus arborum, fruticum, herbarum, Animantiumque terrestrium, uolatilium & aquatilium …  (Frankfurt, 1551), the herbal did not solely focus on plants but also included some descriptions of animals, birds, fish and metals. The emphasis throughout the book is on how one uses animal, vegetable, and mineral substances in the production of medicinal, gastronomical, and household preparations.

Although much of the work was not original to Lonicer it proved to be the greatest printing success of the Egenolph firm. It was one of the most enduring publications of its kind and was still being produced in Germany in 1783. The text covers much of the known natural world at the time and had a wide audience that included physicians, apothecaries, and both rural and urban householders. Lonicer provides us with one of the early descriptions of local flora and he is one of the first to distinguish deciduous trees from conifers. That seems obvious to us but at the time it was unconventional.

The most striking features of this book are its hundreds of hand-colored woodcuts. As you can imagine coloring in each image is an intensive task and would have greatly increased the cost of the book. Colored herbals were relatively rare since they were very costly to produce therefore many early printed herbals were unpainted. There’s the story of the coloring of a Flemish edition of L’Obel’s herbal for the Duke of Prussia, it took three months to color. By the time it was finished it was too expensive for hard-working botanists to buy. 

Lonicer took over the publishing firm after his father-in-law died in 1555. He went on to publish no fewer than four editions of his Kräuterbuch between 1557 and 1577. This Renaissance botanist died at Frankfurt-am-Main on May 29, 1586.

So, what plant genus is Lonicer’s name associated with?
A few hints:
It’s in the Caprifoliaceae family and native to North America and Eurasia.
There are about 180 species identified in North America and Eurasia.
It’s a widely cultivated ornamental garden plant.

If you guessed Lonicera, you’re correct!
Members of the genus are commonly known as honeysuckle, named for their sweet nectar. Lonicera are prized for their fragrant flowers with some bearing edible fruit. Many creatures, both day and night feeding, use them as a nectar source. While honeysuckle is a favorite landscaping plant many species can be invasive or grow so heavy they overpower their supports or trellis. Choose varieties wisely and monitor their growth.

This week is the end of 2021 and the start of the new year. What a year 2021 has been! Without even talking about politics, COVID-19, sports, or the economy, it was certainly one to remember from the standpoint of weather and climate. No matter where you live, you probably saw some extreme weather during the past 12 months.

Exploding flower bed fireworks, Eric Kilby via Commons Wikimedia.

Extreme weather in 2021

In the United States, the map below shows just the 2021 billion-dollar disasters through October 8. That does not include the tornadoes that ravaged the Midwest, including Mayfield KY, in early December or the fires that burned through the suburbs between Boulder and Denver CO, earlier this week, since those losses have not yet been tabulated. This also does not include the terrible disasters that happened in other parts of the world, such as the devastating spring frost in France’s wine country or the awful flooding in parts of Germany and Belgium last summer. While there is no doubt that a warming climate is partially to blame for many of these disasters, we are also putting ourselves in harm’s way by building in areas that are prone to flooding, wildfires, and other natural hazards that can lead to human disasters. Even if the climate were not changing, we are making matters worse by putting ourselves at higher risk in the way we build and develop land.

Looking back over last year’s climate

Climatologists are generally very busy this time of year, since everyone (especially the media) wants to know how the year that just ended compared to previous years. While it usually takes a few days for the preliminary data to be complete, and a few months before the final quality-controlled data are available, we can take a quick look at the past year using online tools like the High Plains Regional Climate Center’s ACIS Maps that compile climate information into simple displays. The map below shows the percentage of normal rainfall for 2021 across the contiguous United States. As usual, there are areas with very wet conditions and areas that received less than a quarter of their expected precipitation. Sometimes those areas are not very far apart—just compare southern California with Arizona right across the border. Does the map agree with what you experienced?

If we look at the temperature map below, it shows that very few areas in the United States were colder than normal temperature. What makes this particularly concerning is that our normals were just updated this year, as I discussed in an earlier blog post. Because the temperature trend across the United States is upward, not flat, we can expect to see more years above than below normal in the future. This is leading to concerns about increased water and heat stress on gardens and gardeners who are working outside as well as damage to natural ecosystems not adapted to the warmer temperatures.

Reviewing your garden in 2021

New Year’s is a great time to evaluate the past year and plan for the next twelve months in your garden, too. If you have the chance, take a walk through your garden and see how it looks (of course, that assumes it is not covered by snow). How did your plants, shrubs, and trees do this year? Are new plantings well established, or do they need to be moved or replaced? Are your new trees correctly planted and growing well? Are you maintaining soil health and moisture with appropriate surface cover? If not, there is plenty of advice on how to correct problems in this blog—just do a search to find information that is based on current science, not hype. It’s also a great time to think about what you will be doing with your garden in the coming year. Perhaps the warmer temperatures will allow you to try new plants that you have not been able to grow before. I know many of you are already looking at the new seed and garden catalogs for next year, so dream away!

Don’t forget to prepare for bad weather, too

In addition to your planning for next year’s garden, don’t forget to prepare for extreme weather, too. Have a plan for where to go when severe weather threatens, and how to contact each other if you are away from home when it strikes. Keep an eye on weather forecasts so you know when conditions are likely to threaten. Have multiple ways to get severe weather warnings, including a NOAA weather radio and a cell phone that is charged and ON with the volume turned up and an appropriate warning app or two loaded. Don’t count on an outdoor siren to wake you up—they are not designed to warn people indoors. Get helmets to protect your heads from falling or flying debris if you can. Make an inventory of your household goods and store it somewhere safe (a good idea for any disaster, not just a weather event).

See you in 2022!

I’ve enjoyed sharing some of my weather and climate knowledge with you over the past few months and look forward to continuing this in 2022. I’ve also learned a tremendous amount from my co-authors and know that you have, too. Enjoy the rest of your winter holidays! I hope that your 2022 is beautiful, safe, and productive for all of you and your gardens too.

Auntie Mame was on to something when she told her orphaned nephew Patrick to “Haul out the Holly, Put up the Tree Before My Spirit Falls Again” (I just sang this in a concert with my community chorus.  I’ve been hauling out the holly since August, so I’m done.) 

Plants play a big part in our holiday traditions this time of year.  When it comes to decorating for the holidays, needless to say I prefer a simpler, natural approach. The best inspiration — and materials — come from nature and sometimes from your very own landscape. It is no secret that the celebration of Christmas was timed by early church leaders to coincide with other ancient winter festivals that predate Christianity.  It made it easy to get everyone to join in the celebrations. 

Saturnalia was a Roman festival that celebrated Saturn, the deity of agriculture, and the harvest. Yule was a 12-day midwinter festival celebrated by Germanic pagans into which Pope Julius I inserted Christmas in AD 336 (there was no celebration of Christmas until then), giving rise to the 12-day Christmastide festival (or Yuletide, depending on where you are). The celebration of the winter solstice is also of pagan origin, a celebration of the darkest, or shortest, day of the year (in the Northern Hemisphere) and the rebirth of the sun.

Many of these festivals included the bringing of evergreens and natural elements indoors to celebrate the connection between humans and nature. They were a sign that life would return after the cold, harsh winter. And also a way to bring a little cheer indoors to brighten up the home during the cold, dreary winter. 

If you look at many of the more traditional elements of Christmas, you’ll notice their connection with nature, and specifically plants — evergreens, holly, amaryllis, poinsettias and more. Of course, the star of the show is the Christmas tree. Christmas trees as we know them didn’t debut until the 16th century in Germany.

A prickly holiday tradition

I’ve written about several holiday plant traditions over the years, each a different way to look at a plant that or plants that bring tradition and cheer into the home.  Perhaps the most popular of these articles is about one of the most recent additions to the holiday plant family – cacti.  The interest in this holiday plant is surging thanks to the interest in houseplants at the moment.  This is making an issue I pointed out several years ago in the article A Cactus by Any Other Name: A Case of Mistaken Holiday Cactus Identity about the mis-naming of cacti even more important.  There’s a Christmas cactus, but there’s also a Thanksgiving cactus (and an Easter one, too). 

Thanks to years of marketing and selling Thanksgiving cacti as Christmas cacti (since they bloom early enough for the Christmas shopping season and actual Christmas cactus bloom closer to Christmas), many people confuse the two.  This isn’t a big issue for the casual holiday plant shopper, but for those that “collect” the plants it can be an issue trying to sort out which is which.  For example, someone recently posted in a local plant group that they were looking for a Christmas cactus.  Half the responses were telling them where they could buy a Thanksgiving (more commonly called Zygo cactus after the zygomorphous shape of the flower) cactus and the other half were asking if they meant that they wanted a true Christmas cactus or a Thanksgiving cactus. 

As romantic as poop on a stick

As holiday plant traditions go, the hanging of mistletoe has to be both the most interesting and weirdest.  As tradition goes, if two people meet beneath the mistletoe they’re supposed to kiss.  How did kissing become associated with a toxic plant that parasitizes trees and whose name translated from the Anglo-Saxon means “poop on a stick” from the fact that the seeds are spread by bird droppings? 

As I shared in The Myth, the Legend, the Parasite: Romance, Lore, and Science beneath the Mistletoe, Norse legend has it that the goddess Frigga (Frig, or Fricka) made everything on earth promise to not hurt her beloved son Baldr, but she forgot to ask mistletoe since it was so small and innocent looking.  Baldur’s brother, the trickster Loki (you know, the one in all the movies these days) made a spear of mistletoe and that ended up killing Baldr. The white berries of mistletoe represent Frigga’s tears, and she decreed that the plant should represent love and that no harm should befall anyone standing below it.  And there you have it.

The flower that’s really just a bunch of overachieving leaves

Most recently, I shared a bit of history and lore around poinsettias, that common but prissy holiday plant that most people can’t keep alive more than a few weeks.  I mean, the original Aztec name for the plant, cuetlaxochitl (ket-la-sho-she), can be translated as meaning “flower that withers” or “mortal flower that perishes like all that is pure”, so the reputation fits. The actual flowers of the plant are the ugly little greenish-yellow bits in the center, which are highlighted by leaves, called bracts, that change colors to bright red (and more colors now) as the flowers develop.

The flower and the bright red represented a gift from the gods for the sacrifices that the Aztecs would make to them. You can read a bit about the history, and how to save them and get them to rebloom from year to year (if you dare) in my festive little ditty Poinsettias: from ditch weed to holiday super star (history, lore, and how to get those d@!% things to rebloom next year).  Of course, there’s been recent discussion on how the story of the poinsettia is similar to the pagan traditions associated with Christmas – a plant tradition of the Aztecs was changed as a way to fit with the Christmas story and work as a conversion tool. It is good to know a bit about the original tradition of the plant to understand its importance throughout history. 

Haul out the holly….and the magnolia….and the rhododendron…..

Holiday plant traditions don’t stop at those finicky plants we grow in greenhouses- the original traditions of Solstice and Yule consisted of bringing in all different types of plants for the season. Sometimes you have to look no farther than your yard to find natural elements fit for a holiday celebration. If you have evergreen trees or shrubs in your landscape, they can easily be incorporated into holiday arrangements indoors or out.

While you can readily purchase live Christmas greenery at many retailers and markets (except for this year, with all the supply issues going on), what you can harvest from your own yard or nearby woods (where permissible) will be much fresher and last much longer. Remember that harvesting branches from your own trees and shrubs is actually pruning them, so you can kill two birds with one stone.

Both white and Virginia pine make excellent decorating choices as they are long-lived and retain their needles well. Junipers, cedars and firs all have interesting foliage and wonderful evergreen scents. Junipers can sometimes be found with berries and cedars sometimes have tiny cones. Spruce is a great choice for wreaths, as it is bristly and holds its shape.

Decorating doesn’t have to be left to the needled evergreens, though. Holly is a classic choice, but mountain laurel, rhododendron, boxwood and magnolia and many others can provide beauty and elegance in holiday displays.

You don’t even need to stick with green things in your decorating, either. Attractive bare branches, plumes from ornamental grasses and other “brown” things can add contrast. Other natural items, such as fruits, nuts and pinecones can also be incorporated for color and interest.  Just take a look around your yard or neighborhood to find those natural elements to bring indoors.

To keep your greenery fresh, there are some basic tips that you can follow:

• Use sharp pruners to make cuts, and keep the ends of branches in water until ready for use.
• Soak evergreens in water overnight to absorb moisture and extend shelf life.
• Keep arrangements in a cool location until use.
• Keep evergreens out of sunlight to reduce moisture loss.
• Use an anti-transpirant spray to keep in moisture.
• Don’t decorate too early — live plants have a limited lifespan.
• If purchasing plant materials, select healthy, green plants and flexible needles/leaves.

Very large and old trees don’t often attain size and splendor free of defect and disease. A mature tree may have accumulated some damage, injury or disease along its path to grandeur. It can contain hazardous branch attachments that have not failed yet, large sections of dead wood or it may bear the burden of an assemblage of cables and other devices installed over the years to sustain it. Very old mature trees have endured perhaps multiple human lifetimes of exposure to storms, droughts, pests and, perhaps worst, early pruning practices. Trees gain age and majesty when they don’t fall down or fail multiple large branches. To do this trees defend their wood biochemically from invading fungi. Trees also cover over decayed wood with new wood that is fairly impervious to the old infection. High vigor trees with adequate resources (water, soil, sunlight) should be able to contain decay that would shorten their lives otherwise.

Dr. Alex Shigo (2003) devised a chart showing the amount of pruning over a tree’s life time. Young trees have all living cells and most of the wood is sapwood, therefore the trimmings in young trees are of living tissues. As trees grow older and shade themselves heartwood develops in the canopy. It’s not living, doesn’t conduct water and minerals but does provide support to branches and strength to the canopy. Heartwood is also more resistant to decay than sapwood. The pruning of a mature tree removes a combination of living and dead cells. An over mature or ancient tree has much more dead cell tissue and only deadwood should be removed with an attempt made to preserve all stems with leaves.

Large trees have large branches and the temptation is to remove large branches to achieve pruning objectives. This would get more done and we would then have to prune less, right? But this is a flawed strategy and the results are the opposite of what the tree owners are trying to achieve. As trees get large, pruning cuts should be smaller and occur frequently. Guidance can be given to branch growth by many small cuts rather than large ones. This approach directs growth without causing rampant regrowth of dormant or latent buds. Latent buds have a purpose, they rescue trees from death should there be a catastrophe. They are preformed along large branches and will sprout when exposed to sunlight or when the terminal buds are removed. Large topping or heading cuts typically activate latent buds and the tree subsequently grows back too many branches in one place. These require selection and careful removal over time and can involve quite a bit of repair pruning to fix the tangle cause by massive heading cuts. Aging trees develop an extensive heartwood that is easily exposed to decay from large pruning wounds so large cuts should be avoided.

Larger trees develop more sapwood which needs energy for respiration relative to the amount of leaves in the canopy. The first duty of the leaves is to provide energy to keep all the cells in the young phloem and sapwood metabolically active. A typical tree only utilizes a few growth rings of sapwood for water transport and energy storage. As these rings age they narrow and there is less tissue from which to store and retrieve energy. Despite the subtle balance between canopy and energy utilization trees continue to grow throughout their lives at more or less the same rate. As trees age the amount of non-functional wood increases, this may be heartwood or deadwood in the canopy. At the end of their lives trees have nearly no living sapwood and the energy of the tree is mostly depleted. Over pruning causes further energy depletion. Removing leaves and buds that give rise to leaves from old trees reduces the amount of energy stored. This forces the tree to utilize sapwood reserves to recover from the pruning losses of the photosynthetic part of the tree. Severe pruning in old trees ultimately depletes them of stored sugars and leaves them without energy to make defensive compounds. This can exacerbate conditions by allowing disease or decay organisms to enter the sapwood.

What if your large tree was never structurally pruned and has branch faults or you have concerns for failure? You should always consult a certified arborist with training in Tree Risk Assessment. The health of the tree is important but the safety of those living around it is more important. Sometimes targeted pruning can be used to shift the balance of growth in a tree and strengthen branch attachments. This can take years of careful pruning with small or modest cuts. When large branches must be removed they should be left as long as feasible and the cut should be circular not an oval shape to decrease exposed surface area. Large pruning wounds should be limited to the fewest number required to achieve the pruning goal. Pruning paints and wound dressings are not recommended.

Large trees accumulate deadwood during natural senescence of inner branches or due to injury, disease or insect attack. Common practice has suggested removing deadwood from old trees but as arborists become more sensitive to urban ecology issues we realize that deadwood is prime habitat for cavity nesting birds and other life. Deadwood serves a purpose and, if it does not pose a threat to those living under or around the tree, it should be retained especially if evidence of utilization is present.

Caring for large trees is tedious because there is a lot at stake. Old trees are valuable and provide many benefits to their owners. Always seek expert opinions and be willing to pay for them, preferably from the arborist who does not do the pruning. Then act on those opinions with care and consideration and always closely supervise any pruning being done to your trees.
Use the following pointers from Gillman for mature tree pruning strategies:
-Evaluate your tree for health, strong branch structure and evidence of decay
-Remove dead branches as needed but retain some for wildlife if needed
-Perform structural pruning when feasible
-Shorten or remove branches with cracks swellings or deformities
-Remove parasites such as mistletoe or canker infested branches
-Retain as much live tissue as possible while achieving pruning objectives
-Keep cuts small (2inches) or moderate (4″) if the tree is a good decay compartmentalizer

References:
Gillman, E.F. 2012. An Illustrated Guide to Pruning 3rd ed.
Delman Cengage Learning, Clifton Park, NY.
Manion, P.D. 1991. Tree Disease Concepts. 2nd ed. Prentice-Hall, Englewoood Cliffs, N.J.
Shigo, A.L. 2003. Modern Arboriculture A systems approach to the care of trees and their associates. Shigo and Trees Associates Durham, NH. 3rd ed.