TREES & Plants

How and when to water

Here are some tips from The Morton Arboretum on watering trees and other plants.


  • Check the soil. To check the soil's moisture, either use a soil probe or place your finger in the soil. If it is dry and hard, watering is appropriate. If there is some moisture, continue to monitor the soil's moisture level.
  • Water weekly. Gardeners should continue to water plants weekly. Prioritize watering needs. Start with newly planted trees or those planted within the last 2-3 years. Large, established trees should be watered every two to three weeks in dry periods. Don't forget the trees on your parkway. They need water too.
  • Water the roots. The Arboretum recommends watering within the drip line of a tree, from the trunk out to the end of the branches, to reach the roots most effectively. The water absorbing roots are within the top 2 feet of soil. The objective is to keep roots moist but not wet.
  • How to water. Avoid frequent light watering. Let a hose run slowly at the drip line of the tree, moving it around occasionally. At medium pressure it will take 5 minutes to produce 10 gallons of water. If using a sprinkler system, place a container nearby and let it fill one to two inches.


  • Check on these species. Drought-sensitive trees and plants likely showing the effects of reduced moisture include magnolias, Japanese maples, dogwoods, beeches, larches, tulip trees, and birches. Also, hydrangeas are likely suffering because they're shallow-rooted and therefore drought-sensitive. Watering one to two inches will percolate into the soil about 6 inches reaching the fine water absorbing roots.


  • Water container plants more frequently. Container plants can dry out and wilt fairly easily; they should be watered frequently. If plants are in full sun, they likely require more water than containers in shade, which can retain water more easily.


  • Check new plants and trees frequently. Newly-planted trees, shrubs, and perennials are still establishing their root systems and should be checked more frequently. Water into the root ball area and surrounding area deeply. This will encourage new roots to grow deeper into the soil. Plants should receive up to one inch of water weekly.
  • Use "Gator Bags"–plastic, water-filled vessels that surrounds a tree trunk–provide a slow drip to the root system and are a good way to keep your younger tree well watered.




  • During drought trees should have priority over your lawn. In drought situations, your grass will go dormant but if severe drought continues you may want to apply a ½ inch of water to keep the crown of the grass alive.


  • Mulch. Remember to keep two to four inches layer of organic mulch around a tree to moderate soil temperature and retain moisture. Do not let it touch the trunk or stems.

For more information, visit The Morton Arboretum Plant Clinic or call 630-719-2424.