As quirky weather patterns would have it, our part of Pennsylvania went from super-soggy wet in early summer, to cracked-soil dry in late summer.
Yesterday, I saw a man unrolling a soaker hose beneath a row of Burning Bush hedges, to give them a good Sunday drink. We’ll call it “shrub tailgating” ahead of the football game, played later in the afternoon.
So on this first day of Autumn (aka “Where did summer go?”) you might be wondering at what point you should water established trees and shrubs that are under water stress. I use the word “established” because watering instructions for newly planted landscapes is still “once a week if measurable rainfall has been less than 1-inch or 2.54 centimeters.”
Established plants don’t need the same level of baby-sitting, since they have root systems that reach further. Plus there is always the concern that watering too much in late summer, may create new growth, which doesn’t properly harden-off for winter cold. (The same reason you should quit fertilizing woody ornamentals after July 4th)
So what is the proper balance with watering in late summer on drought-stressed plants?
HOW MUCH WATER?
First of all, anytime you water landscape plants, it should be a thorough, deep watering, which can be difficult when the ground is “cracked-soil dry” since dry soil and wood mulches repel water.
That’s why a soaker hose is a good idea, since it applies water very slowly, provided it is left running long enough. It might even need to be moved to a second and third location to adequately water more of the root zone.
Keep in mind, that on average, most of a tree’s feeder roots are on both sides of the “drip zone” -- the tips of the branches. Focusing the water in that area, slowly, and for a long enough period of time, will do the job.
WATER HOW OFTEN?
Finally, the big question of how often you need to water established plants during a late summer drought. There are many variables, such as what type of soil, high temperatures, wind speed, and where that particular plant is growing, but in our clay western Pennsylvania soils I would say once every 3 weeks, on average.
Any trees and shrubs planted within the past 3 years should probably be watered thoroughly every 2 weeks, on average. Your plants will show their appreciation next spring, as they begin a new growing season with robust flowers and foliage!