Susan Kierstead offers the following thoughts (in italics) on our current drought and how to best mitigate the damage in your gardens:
This drought has been making me crazy. That is the understatement of the year. We have 2 wells, but even then we can only water for less than 1.5 hours in AM and PM using 3 sprinklers. If we did all the gardens, it would take 7 or 8 days. Thus I am going into defensive mode. Remote gardens are on their own. Vegetable garden takes precedence. Gardens I see from my coffee nook take precedence. And it’s still not enough. I am sending you my drought letter, which I know I have sent many times before. One thing I have added is cut half of each leaf in big leaved plants. I am starting that now.
New Hampshire has experienced several periods of drought over the last several summers. During these dry periods, plants experience physiological strain due to water deficit. At least one inch of water a week is essential for maximum growth. This applies to herbaceous perennials, trees and shrubs. Seedlings are most susceptible to drought because they have shallow root systems which dry out quickly.
Plants are constantly transpiring (giving off water through the leaves) and absorbing water from the soil. Warm windy days increase transpiration. When plants give off more water than they take in, a stressful situation occurs. At night, water absorption exceeds transpiration and the plant will regain water from mist or dew only to be depleted the next day. If the leaves are wilted first thing in the morning, then that plant could be in trouble.
If water is not replaced in the plant cells quickly, the cells degenerate and die causing different effects in different types of plants. The weakened plant is now a target for insects and disease which may be the final cause of plant loss.
Prevention is the best defense for drought stress. Soak the root ball if it appears dry before you plant. For trees and shrubs, fill the hole with water first. Always water seedlings and transplants. For perennials, water well the whole first season, even if it is a drought tolerant species. For trees and shrubs, plan on a 5 year period for them to become established with extra watering. When dry periods occur, start watering about 2 weeks after the last heavy rainfall. It is best to give thorough waterings less often, than to just wet the surface layer. As I’ve said before, check that you’ve watered deep enough. Stick your fingers in the soil. We use a lot of natural mulches and not only do they feed the soil, they prevent water loss due to evaporation and will regulate soil temperatures.
If you can’t water, then your best defense is to do nothing. Do not cut plants back or fertilize them to give them a boost. Both helpful acts have a negative effect on stressed plants. Fertilizing burns the stressed out root hairs. Cutting back seems more logical, but once cut, a plants’ natural growth pattern is to replace the cut off limb with two branches where one was previously. Symptoms of stress such as browning, or curling of leaves, or even yellowing are part of a plants’ natural defense system, and in the long run are the only defense if extra watering is not feasible. And I admit, it is extremely difficult to constrain oneself and not cut back. It really hurts to see brown leaves, but it is part of a built in mechanism that plants have perfected over the years. Of course, if the plant has to suffer drought repeatedly, it will not be able to cope. I watched a particularly favorite aster dry up, top to bottom. It was hard not to do something. When it rained in late August, leaves sprouted up all along the stem. No it didn’t bloom, and yes it survived the winter of 2015,’16. Now an exception to the ‘do nothing’ rule is plants with large leaves. Here I go around and cut off half of each leaf. This way the plant does not feel the need to make more leaves, but there is less leaf area to lose water. It’s unsightly, but it works. This is a regular occurance with a hellebore that is in too much sun. The leaves were flat on the ground for days before I bit the bullet and trimmed. It stood straight for the rest of the summer, and gave it’s best bloom ever the next year. Wonder what will happen if I have to repeat this yearly?
Woody plants stressed by drought may also not be as winter hardy as they need to be to survive a particularly harsh winter. If it has been a dry summer, make sure the plant has been given a good watering before the ground freezes, and maybe even a pine needle mulch to help get through the winter.
Also, thanks to Jeanne Nevard for providing this beautiful photo she took in Pepperell, MA (which she also submitted to the Channel 5 News).
The Amherst NH Garden Club 