We just put in a large new garden with a mix of trees, shrubs and perennials. A sprinkler system is being installed next week, and I would like some advice on how best to set up
the system.
— Jeff Levine, Skokie
Congratulations on your new garden and on recognizing the importance of proper watering while it’s being established. The sprinkler system will make the job of watering easier and less time-consuming for you, but it doesn’t eliminate the need for you to monitor your new plants and spot-water as needed. Watch for plants that are wilting, turning an off-green color, or losing leaves; these are signs that something is wrong, and you’ll need to do a little investigating. Wilting leaves are usually the first indication that the plant is too dry, and they’re pretty easy to spot. In general, these symptoms indicate a plant is too dry, but the tricky thing is that too much water can have a similar effect. Check the root balls of the plants to determine if they really are too dry.
An automatic sprinkler system using misting nozzles may not deliver enough water to balled and burlapped plants and running a system long enough to soak the root balls regularly can overwater other plants. Watering the base of the trees and shrubs with a hose every couple of weeks in tandem with a sprinkler system should be enough. It’s hard to give specific guidelines, of course, since different gardens will have different growing conditions, and the plants will also have different needs. The key thing is to monitor the new plantings and spot-water when they need it. As the weather cools down in the fall and plants start going into winter dormancy, they will require less water. Newly planted evergreens do need supplemental water in November, though, if the weather is warm or dry. Evergreens that go into the winter season under drought stress are more likely to suffer winter damage.
You’ll want to make sure that the sprinkler system covers all the plants in the beds. A few gardeners I know told me that a lack of water couldn’t be the reason their new plants died, because they were watering three times a week with their sprinkler system. But then we watched the coverage when the system was running, and the “dead” plants were barely getting any water from the system — definitely not enough to establish a new plant. Also, several gardening friends underwatered new hydrangeas grown in containers that they planted while in full flower; I’ve learned that container-grown hydrangeas planted in full flower need more frequent watering to get them established — two to three times per week.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.