Thirsty Plants Fall Prey to Winter
Only long watering will save drought-stressed plants
August and September are the months when trees, shrubs and herbaceous perennials absorb the most water in preparation for winter. July’s drought has so stressed landscape plants that unless you water heavily these next two months, they are likely to suffer serious winter injury, even if the winter is mild. Waiting to irrigate the trees and shrubs until October and November is too late.
Both research studies and experience have repeatedly demonstrated that if trees, shrubs and perennials enter winter without adequate moisture in their tissues, they will dehydrate, causing the bark to split and exposing the inner tissues to the elements. Since we are currently eight-plus inches below our average rainfall, plants are already under severe drought stress. Shallow-rooted species such as azaleas, dogwoods, hollies and boxwoods are already exhibiting signs of wilting and curling leaves. These days, it is not uncommon to find leaves with brown crispy margins. Unless such stressed plants are irrigated deeply, they will be dead by fall.
For adequate irrigation, you’ll need lawn sprinklers and soaker hoses. The worst thing you can do is water these plants by hand (unless you are willing to do so for hours). Allow sprinklers and soakers to remain in place for at least three to four hours. If you are using a sprinkler and wish to maximize your water use, turn them on around 7pm and run continuously until about 10pm. Moving the sprinkler to a new location and letting it run until morning will ensure a good deep soaking of the soil. Large shade trees, especially those growing along salt or brackish water, need heavy watering to prevent their roots from absorbing saline water. When soils are dry, water from the Bay infiltrates into surrounding soils.
Soils are dry; turn on the water.
Alas, Mimosa and Black Locust
Q I picked up an old issue of Bay Weekly [Vol. xv, No.6: Feb. 8, 2007] yesterday and read your article regarding what trees not to plant in your yard. Two of the trees in this category were the black locust and mimosa, among my favorites. Can you tell me why they are bad choices for Southern Maryland yards?
K. Oakley, via email
A Black locust is short lived, with a lifespan of 15 to 20 years. It is susceptible to breakage by wind, ice and snow and very susceptible to leaf miner and stem borer. Mimosa is another short-lived tree and is highly susceptible to mimosa wilt.
Foster Hollies Behaving Badly
Q The Foster hollies we planted at a residence in Georgetown are losing their leaves. They will be replaced, but I was wondering if you recommended a different holly or shrub that had similar characteristics or was simply a hardier holly for that location,
Jo-Elle Burgard, Clinton & Associates, PC Landscape Architects
A I find it hard to believe that Foster No. 2 is giving you trouble. I have grown that plant for many years in experimental plots and at my own home without any difficulty except where the soil is too acid, too alkaline or too wet. Were the plants planted too deep? Were they mulched too heavily? Have you had the soil tested to see what the roots have to grow in? As for a substitute with their features, I am at a loss.
Ask Dr. Gouin your questions at firstname.lastname@example.org. All questions will appear in Bay Weekly. Please include your name and address.