Plant Stress

Helping Plants During the September-October Drought

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By Pamm Cooper, UConn Home & Garden Education Center

A sloped yard showing signs of drought stress.
Drought stress on a sloped lawn. Photo by Pamm Cooper

Here at the UConn Home and Garden Center we have been getting questions about lawn and garden issues that have been particularly widespread in the state. Whether in the landscape or the garden, there is always something going on, good or bad, and keeping up with pests or cultural issues can be challenging. Because of the extended late season drought conditions this year, plants may be showing signs of stress. There are some basic things homeowners can do to help plants go into winter as healthy as possible.

Plants in temperate climates, like we have in New England, are normally manufacturing food to enable carbohydrate storage for new growth that will occur next spring. To do this, plants need both sunlight and water, and our extended drought conditions have limited most plants to enter survival mode, and carb storage is a second priority. The best way to help your plants is to water deeply any that still have green leaves. People with wells may need to determine if this is a priority for them. We can hope for a warm winter or insulating snow cover to help any plants with shallow roots survive until warm weather returns.

Drought stress on dogwood leaves
Drought stress on dogwood leaves. Photo by John Ruter

One sign of drought stress in woody broadleaf plants is leaf edges that curl upward. This is a good clue as to the beginning of water stress. Make sure to water these plants deeply, to ensure roots will be able to pick up the water. Usually the next day, leaves will start to uncurl if adequate water is applied. If drought stress continues, leaves may turn brown at the edges and early leaf drop may occur.

Evergreens, even established ones, can benefit from regular watering as long as the soil is not frozen and drought conditions remain. Evergreen foliage, whether needles or leaves, photosynthesize all year, and it is important that soil is not dry. Normally, we have snow that melts on and off, and if soils are not frozen, roots will be able to take up water and photosynthesis can still take place.

Perennials of certain species may be doing fine in this drought. Yarrows, some ox-eyed daisy cultivars, obedient plants, goldenrods, mountain mints and Agastache may be showing no signs of stress. Still, if any have green leaves at this point, consider watering them if dry and warm conditions continue.

This weekend I planted a small shrub, and I had to dig about fourteen inches down to accommodate the root mass. I have to say that I was surprised that the soil, not particularly one that dries out often, was powdery to the bottom of the hole. If you are planting anything now, make sure to water the soil thoroughly as you fill in the area around the roots, then water again when done. This is especially needed for small trees and shrubs but do the same for perennials.

Next year, woody plants that were impacted by drought this year may be more susceptible to certain diseases like verticillium wilt, Nectria canker and evergreens to Rhizosphaera needlecast. Be vigilant and scout for any signs or symptoms of these diseases.

Lawns that did not receive any rainfall or supplemental watering during the past two months may be dormant and crunchy at this time. It may not be clear if the grass will recover when temperatures cool and adequate water is applied. Some grass species may be dead, but it may not be clear until next spring when they fail to green up. There still may be time to apply supplemental irrigation, and with warm temperatures, grass may or may not green up, but at least the crowns may be kept alive to generate new leaves next spring. If any lawn areas were seeded in late summer, water new grass as needed. If it is wilting, water it for sure.

Be alert to what is happening in your own backyard, for the sooner you discover any problems the better. Contact us at the University of Connecticut Home and Garden Education Center for advice on lawns, landscapes, and other gardening subjects. Here's hoping for some needed rainfall and cooler temperatures to help our plants recover from the trying drought of 2024.

Penn State Extension has a good article on long-term effects of drought stress- https://extension.psu.edu/the-long-term-impact-of-drought-on-trees-and-shrubs

If you have questions about caring for plants during a drought, or if you have other gardening questions, feel free to contact us, toll-free, at the UConn Home & Garden Education Center at (877) 486-6271, visit our website at www.homegarden.cahnr.uconn.edu or contact your local Cooperative Extension center.

Is Early Leaf Drop an Indicator of Tree Health?

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By Nick Goltz, DPM, UConn Home & Garden Education Center, Plant Diagnostic Lab

Trees showing their autumn colors
Trees showing their fall colors. Photo by Nick Goltz

The autumnal equinox, one of two times of the year at which day and night are equal in length, just passed on Sunday the 22nd. While this point marks the astrological start of fall, many of the trees lining the roads on my drive to work (and in many of our clients’ yards) seem to want to get a head start on the season. Since late August, we’ve been getting calls from folks across Connecticut asking why the leaves on their trees are changing color and falling early. You may even be thinking, “Hey, a few of my trees are dropping their leaves early too. Is that something that can indicate how healthy they are?” In a word, maybe!

First, let me share the good news that, for most trees, premature color change and leaf drop doesn’t mean that they are in any immediate danger. Plants, much like humans and other animals, respond to stress differently depending on their environment and the kind of year they’ve been having. Just like we might see a little hair loss after a particularly stressful few months, trees may drop their leaves early as a response to stress. Identifying what is causing the stress however, is important when deciding if concern is warranted.

What type of stressors might be causing this early color change and leaf drop? For most trees, the answer is water. Connecticut and several other states in New England had a series of heavy rain events and flash flooding throughout the summer. While we’ve had hardly any rain in the land of steady habits for several weeks now, for many trees, the damage has already been done and symptoms are just appearing now. Saturated soils deprived plant roots of oxygen, damaging them and making them more susceptible to disease. Plants in especially low-lying areas, caught in floodwaters, or grown in poorly-draining clay soils likely experienced the most damage and earliest leaf drop.  Some plants may have even perished outright from the damage. Besides water, excessive heat and the increased prevalence of fungal and bacterial diseases, as well as some insect pests, may have also contributed to the stress our plants are letting us know about now.

So, how can you know if the early color change or leaf drop is an issue for your favorite tree or just its way of complaining about a stressful summer? When and where the leaf change and drop is occurring can help you determine if the damage is likely a normal stress response or due to something more sinister.

Consider when the color change and leaf drop first began. In this instance, seeing some leaves begin to change in the last week of August is less concerning than seeing them change at the end of June. Plants that have their leaves change color and drop in midsummer or earlier are most likely dealing with a disease or pest issue, rather than a stress response. I recommend you get advice for these plants by contacting the UConn Home & Garden Education Center and remove them from your garden if they are unlikely to recover.

Also, consider what part(s) of the canopy was affected. Conifers such as white pine drop their leaves (we usually call them needles) in response to stress too, but you will typically see this take place on the interior of the plant – the older needles that aren’t capturing much sun anymore. Branches on deciduous trees, such as oak, that are in shady spots tend to drop their leaves early too, and this is normal.

Branches in full sun that lose their leaves very early, while others on the tree remain fine, are a bit suspicious. Mark these branches with tape or string and monitor them carefully as the plant produces its first leaves or flowers in the spring. If these marked branches do not produce leaves or flowers with the rest of the tree, get advice (again, by contacting the folks at the UConn HGEC)! The best option is usually to cut them close to the main trunk, then disinfect your pruning tools.

If you’re concerned about the health of your tree, including as a result of a potential disease or pest issue, practice good fall habits to give your trees the best foot forward next spring! Clean as much leaf litter as possible and remove it from the base of trees that dropped their leaves early. If you suspect the plant is diseased or has pests, throw away these leaves or burn them before composting. For example, many plant pathogenic fungi can survive the winter on fallen leaves and reinfect healthy plant tissue the following spring. It’s also a good idea to minimize added stress for your plants. Try not to expose them to herbicides, deicing salts, fertilizers, or other chemicals until they’re looking strong again.

If you aren’t sure how to proceed with your fall cleanup or if you’d simply like a second opinion on your favorite tree, get free horticultural consultation from the UConn Home & Garden Education Center by emailing ladybug@uconn.edu or by calling (877) 486-6271.