Assessing Winter Damage

by Stacey Haag

On a crisp morning in late February, I attended a walking lecture by Dr. Martin Stone at The Baker Arboretum in Bowling Green, KY entitled After the Cold: Assessing Winter Damage in Landscape Plants. Dr. Stone is a Professor of Horticulture at Western Kentucky University and Director of The Baker Arboretum.

We began our conversation by identifying characteristics of the three main categories of woody landscape plants: deciduous, evergreen (needle and scale), and broadleaf evergreens. We speculated as to how much damage we may find upon closer inspection of each category within the arboretum. Although it will be a few more months before the full extent of damage from the extreme weather event of Christmas 2022 is known, some damage is already visible.

Although our winters may be mild as compared to much of the country, it's not unusual for Middle Tennessee and Southern Kentucky to see near- or below-zero temperatures every few years. So, why then was this single event -- the worst in at least 40 years -- so devastating? As it turns out, it wasn't simply the 55-degree temperature drop in a short amount of time that caused widespread damage. It's imperative that we also factor in the damage caused by the sustained fast and dry winds of that polar blast.

Next, we ventured out into the arboretum for a closer look at individual specimens. Dr. Stone demonstrated how to inspect individual limbs, checking for flexibility and healthy green and yellow cambium just beneath the bark's surface. A small pocket knife or sharp thumbnail can be used to gently scrape away the bark to reveal the cambium beneath. If the cambium is dark brown or black, that branch of the plant is dead. Opposite sides and lower sections of the same plant should also be tested to determine how far-reaching the damage.

Generally speaking, we observed that deciduous species have experienced little to no long-term damage, unless they were planted outside of their hardiness zone. In needle and scale evergreen varieties, we found mild damage. Broadleaf evergreens (boxwood, aucuba, laurel, nandina, and magnolia), however, have suffered considerable damage. If you have a large, established magnolia on your property, it may not look too bad; however, young or nonnative cultivars may look considerably worse for wear. You may see a similar contrast in holly, for example. If you have hardy American holly in your landscape, it may recover well after a bit of time. However, if you have English, hybrid, or nonnative hollies, they may need to be replaced after this spring. In general, native species will prevail as the real winners following this winter, having made it through relatively unscathed.

So, why might you be seeing a stark contrast of damage within even the same species in your own yard? There are several factors that played important roles during this extreme weather event. As previously mentioned, species that were planted beyond their hardiness zone already have obstacles to overcome in a mild winter, so this event was just too much for many of those to handle. Second, placement within a landscape creates microclimates due to varying levels of exposure to elements such as wind and sun. Specimens that were partially shielded by your home, hedge, fence, or larger vegetation most likely sustained less damage than those fully exposed and will have the best chance of recovery and survival. If you inspect closely, you may even be able to tell the direction from which that extreme polar blast was blowing by comparing relative damage on different sides of the same plant.

It's helpful to understand why broadleaf evergreens were so affected. Because they retain their leaves during winter, continually performing photosynthesis, the stomata, pores that control gas exchange, of these plants were open when the polar blast descended upon us. These evergreens actually experienced drought stress from the harsh, dry wind. Although drought stress is unusual for our area in the winter, it caused arguably more damage than the subzero temperatures would have alone.

Moving forward, your best bet is PATIENCE. This year especially, it may be best to wait to prune until May. If you prune too early, you may end up having to prune a second time later in the season, which will cause additional stress. Plants are always in one of two modes: grow or protect. Growth will be delayed this year, so give your plants the extra time they may need to protect and recover. An extra dose of patience also applies to fertilizing this year. You should never fertilize damaged plants as their root systems cannot take up nutrients. Save the fertilizer for healthy and recovered plants.

Tennessee Tree Day

by Jeff Bayer

Tennessee Tree Day began in 2007 and has been responsible for the planting of over 678,000 native trees, which has successfully added approximately 3,000 acres of tree canopy and life habitat statewide. Annually, Tennessee’s communities have helped make the event become the largest such annual event in America. Year after year, thousands of Tennesseans from all backgrounds are eager to plant trees with what seems to be an endless well of enthusiasm for this event.

The Tennessee Environmental Council (TEC) organizes Tree Day, which is America’s largest community native tree planting event. With 150 local pick-up sites, Tennesseans and Master Gardeners have been organized by the TEC to distribute 100,000+ native trees to be planted across our state and neighboring states.

Tennessee Tree Day involves thousands of Tennesseans in this effort to replace trees lost to development, restore degraded streams, improve water quality, reduce air pollution by capturing carbon dioxide, maintain the health of terrestrial and aquatic habitats, increase available habitat for pollinators and wildlife and ultimately help increase Tennessee’s tree canopy.

Last year, Robertson County Master Gardeners distributed 850 native trees to our communities in our county alone. This year, we are distributing 1,076 trees!

Each year, RCMGA members volunteer to help with assembling the tree orders. This year, we began assembling orders on Friday, March 17, and then helped distribute the trees at the UT Extension office in Springfield on Saturday, March 18. 

This event not only helps the environment of our state, but also helps bring our association to the public eye, potentially creating curiosity about who we are and what we do. Our newest Master Gardeners are going through the prerequisite courses now and have already begun volunteering to help where and when needed.

Holly and I joined the RCMGA to learn more about native plants and how to grow gardens, but we also found a fun group of people who enjoy getting together to help our communities, neighbors, and county.

Our volunteers are our backbone. Their combined generosity makes us stronger, and we all hope and help to continue to make our county a greener, kinder place to live.