January seems like a good time to look back over the growing season of 2019. It was freakish, right? Excessive heat, extreme storms, and unusually long-lasting drought — all the way into October! After the over-the-top rains of 2018, who would have predicted it? Certainly not me, but I’ve learned a few things over the past two summers, and one of them is to expect the unexpected. Unpredictable weather is nothing new, but even more of it is in the offing because we’re now experiencing climate change, In case you missed it, you may want to read last month’s feature article on climate change in central Virginia. piedmontmastergardeners.org/Climate Change Is Happening in Central Virginia.
In early November, with the blistering heat behind us, I surveyed my yard for plants that had survived, or even thrived. You probably did, too.
Here were some of the thrivers in my yard:
cranberry cotoneaster (Cotoneaster apiculatus), N.C.State
rose campion (Lychnis coronaria), Mo.BotanicalGarden
wild bergamot (Monarda fistulosa), Mo.BotanicalGarden
little blue stem (Schizachyrium scoparium), Wildflower.org (pictured above, courtesy of PlantFinder, Mo.Botanical Garden)
Photo courtesy of Purdue Horticulture
Photo: Valerie75, Wikimedia Commons
It’s probably no surprise that my crape myrtles and winter jasmine persevered, shrugging off all that mother nature dished out. They’re not natives, but they sure are tough. Read more at Mo.BotanicalGarden/Plant Finder and at The Garden Shed/Crape Myrtles.
And now I’m asking YOU to help me build a list of the tough plants that are managing the difficult conditions our summers are throwing at them in our new era of climate change. We gardeners tend to be keen observers, and if we collaborate, we can help each other and maybe even build a knowledge base. So please, add to the list by commenting at the bottom of this article or by emailing me at garden-shed@piedmontmastergardeners.org.
We can’t be alone in wondering which plants are tolerating these new conditions, right? So I did some looking about, and discovered that scientists are indeed hard at work on identifying how and why some plants are managing better than others in handling extreme heat, drought and unprecedented precipitation. But I was looking for a “Climate Change Plant List,” and I’m sorry to report that I didn’t run across such a thing.
But the work is definitely going on. One of the best sources I found is called State of the World’s Plants, a yearly project begun in 2016 by The Kew Science department of the Royal Botanic Gardens at Kew, England. I had always thought of Kew as strictly a botanical garden, but it’s more than that; a number of plant scientists work at Kew Science. They are surveying published research and databases and producing annual reports which collect the current state of knowledge about plants and the threats they face, including climate change. A video explaining this project is linked here: youtube/State of the World’s Plants 2017.
The first of these reports noted that a plant has three options in coping with climate change: move, adapt or go extinct. It concluded that “there is compelling evidence for all three processes starting to occur across the globe. Large-scale patterns of changing plant distributions, flowering times and novel community assemblages in response to rising temperature and changing rainfall patterns, are now apparent in many vegetation biomes.” So far, research indicates that the following characteristics enable plants to tolerate the weather stresses of climate change:
- thicker leaves
- efficient water-use strategies
- deeper roots
- higher wood density
I don’t know about you, but I’m not in the habit of assessing a prospective plant for these traits. How exactly do you determine if a plant has higher wood density than others?
There’s another trait that is helpful in surviving drought. Some UCLA biologists recently discovered what makes certain plants more drought resistant than others: the saltiness of their cell sap. Plants have the ability to accumulate salt in their cells, which attracts water molecules, and they adjust these salt levels in response to drought. As researcher Christine Scoffoni explains it: “The salt concentrated in cells holds on to water more tightly and directly allows plants to maintain turgor during drought.” A plant with saltier sap and higher turgor pressure is less likely to wilt and die during drought. Okay, that sounds pretty straightforward, but it’s not.
Plants face a difficult dilemma during a drought: they must “choose between closing their stomata and risking starvation, and continuing to photosynthesize and risking cell damage from wilting,” UCLA Newsroom. Scoffoni and the rest of her team of biologists collected data from numerous species on the “turgor loss point” — the level of dehydration that causes leaves to wilt. Plants that have a lower turgor loss point can lose more water before wilting, and can keep open their pores (stomata) to take up carbon dioxide for photosynthesis in drier soils. Oh, the drama that was silently occurring in our garden beds last summer!
Meanwhile, my list of questions is growing. How do we identify plants with a lower turgor loss point? Is there a list of these species somewhere? How do we choose plants when it’s unclear whether they’ll be adapted to the future climate of central Virginia?
As a starting point, we can look at the plants that are native to the American Midwest and are already adapted to both drought and excess rain. The Chicago Botanic Garden recommends Midwestern natives and has a special shout-out for blue false indigo (Baptisia australis), which has fleshy roots that can go down 25 feet! www.chicagobotanic.org/Weather-Tolerant Gardens. They remind gardeners that a soil rich in organic matter is better-equipped to nourish plants through both drought and floods. Also, they encourage us to focus carefully on HOW we irrigate:
“When rainfall is scarce, irrigating deeply but infrequently encourages plants to develop extensive root system capable of finding every available drop of moisture. But extensive roots also help plants to take full advantage of drenching storms. One inch of water delivered at one time penetrates the top 4 to 5 inches of clay soil, and up to 12 inches in sand. In between deep waterings — natural or supplemental — as soils become dry, roots resume growing in search of life-sustaining moisture. Constantly sprinkled plants become spoiled, and develop shallow root systems that leave them less able or even unable to sustain themselves during drought.“
Plants are definitely adapting — already — to changes in climate. You can read all about it in “Many Plants Can Adapt when Climate Goes against the Grain: Seasonal plants, including possibly the world’s important grains, can adapt relatively quickly to climate change,” Scientific American, Scientific American (D. Biello, 2007). This is good news indeed. Annuals and other short-lived plants can adapt more quickly than long-lived plants like trees.
For now, let’s start developing our own list of “Plants that Withstand Climate Change in Central Virginia.” We can do it; we’re gardeners after all. Please add your survivors and thrivers in the comment section below or email me at garden-shed@piedmontmastergardeners.org.
Sources
Kew.org/State of the World’s Plants & Fungi
“Plant developmental responses to climate change,” www.sciencedirect.com/Dev.BiologyVol 419, No. 1, Developmental Biology, 2016
“How a Few Species Are Hacking Climate Change,” National Geographic, www.nationalgeographic.com/news/2014
“Understanding how plants withstand harsh conditions remains major research challenge,” Phys.org/news/2016