Well, it is your hip, non-hipster gardener, back with his dry sense of humor, ready to chat it up about another timely topic, the importance of fall irrigation.
Believe it or not, despite the recent deluges, much of Indiana is facing abnormally dry conditions for this time of year, with some areas still in extreme drought conditions. This past week, Wellfield received over four inches of rain in a matter of few days, begging the question: why are still facing a drought? Doesn’t that much rain make up the difference? The answer is: maybe. It all depends on the plant, the soil and the weather forecast.
In a normal seasonal dry period, the soil profile slowly dries out to greater depths as plant roots extract moisture deeper and deeper. When rains arrive, a summer storm may only wet the top couple of inches, a fine situation if you have shallow roots such as turf grass, but even a deluge does little to relieve larger woody species like shade trees.
Trees have the adaptive advantage over their herbaceous cousins due to wood fiber’s excellent water storage ability and water loss reduction. Unfortunately, for trees in abnormal drought periods, shallow roots and evaporation make quick work of a passing cloud burst, leaving the soil moisture content in the deeper soil layers dry. It takes either frequent rains or a very long, slow, gentle rain to percolate deep into the ground. This is why watering longer and less frequently is a smarter practice, even with turf. Water less frequently and more deeply, ideally wetting the entire root zone, the top twelve inches of soil.
For the above reason, there have been times in the past two weeks where I continued to run the irrigation systems right in the middle of a shower. I knew the passing storm was wholly inadequate to make up for the extreme dry period. The soil was dry to a much greater depth, so we fired up the sprinklers.
This brings up a last point regarding the importance of making sure your garden, especially newly planted items or plants that struggled through the season, remains well watered into the fall. Roots are still actively growing and need that additional water, even as the plant crown goes dormant. Conifers and broadleaf evergreens like rhododendrons, whose crowns do not go dormant in the same way as their deciduous relatives, also benefit from a regular deep watering as they go into late fall as a precaution against winter desiccation.
If you have failed to start watering, it is not too late. They say to arid is to be human. Before your attention evaporates, I shall leave you to soak up this information.
Josh Steffen, Horticulture and Facilities Manager