This column has frequently addressed the need to water new plantings, transplanted trees, shrubs and evergreens added to the landscape. Little has been written regarding water management on what we would all call our “well-established” landscape plants in the yard.
Most of us give little thought to the idea that those big oaks, maples, pines and spruce could use our help.
The last time the hot, dry weather got our attention was the summer of 2012. There were issues with lawns certainly, yet calls to the volunteer Master Gardeners on taking care of established trees were few and far between.
While large established plants may appear to be OK, a lot of them really are not. I was able to examine a cross section of an oak that had been taken down mid-summer. You could readily see the growth rings from the spring of 2017 and back. Prior to 2012, the rings were wide and evenly spaced indicating good growth rates. From 2012 forward, the rings were very tight together, indicating slowed growth. Until the tree died, the leaves appeared normal according to the homeowner, who had no idea the big, beautiful oak was in trouble.
Short of being able to evaluate the tree rings, you can go out and examine branches to see how much annual growth they are putting on. This mirrors the rings in the trunks. You will need to examine quite a few branches to get a good idea on the average growth overall.
So how do you water such big trees in the home landscape? This will take several hours per tree. An open-ended hose placed in the general drip line of the tree with a strong rate of flow in several areas in the total dripline is needed. It may be easier to think about mentally dividing the area up into quarters, letting the hose run for an extended period to get the whole area done.
The majority of the trees roots that absorb water and food from the soil live in the top 12-18 inches of soil. When it does rain, those roots can take advantage of all the moisture the canopy can provide.
While the canopy of most of our evergreen trees in not nearly as extensive, watering them is very similar, just in a smaller diameter. Watering those established evergreens now is going to help; watering them late in the season just before you hang up the hose for the winter also is very important. Evergreen needles lose moisture all winter, so supplying them with as much water as possible, as late as possible, really helps.
You should not forget your established shrub borders, either. Watering a bed is not as exacting. Move the hose around in the bed until you feel there is water everywhere. Oftentimes, placing the hose between the shrubs works the best.
It might be tempting to put a sprinkler out there instead, but sprinklers cannot provide the same volume of water to your valued plants in the same timeframe an open hose can. Using the open hose also allows you work in other beds doing fall cleanup while your tree, shrub and evergreen watering goes on.
• Richard Hentschel is a horticulture educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. Get more garden and yard updates with “This Week in the Garden” on Facebook at facebook.com/extensiondkk/videos. The 2017 Kendall County Master Gardener Help Desk currently is open from 9 a.m. to 12:30 p.m.Monday, Wednesday and Friday at 630-553-5823 or at firstname.lastname@example.org.