When to water

Question

I have a new ninebark and new autumn blaze maple both of which are planted in different soils. The ninebark has black spots on its leaves and some leaves have died. Soil is sand/dirt. Maple is in clay/dirt/some sand. Here in Wisconsin soils seem to be mixed.
I don’t want to lose these trees!
Watering is a problem – don’t want to over nor under water.
Thanks. Cheryl Breeden

Answer 1

Most of a tree’s feeder roots, the tiny roots that absorb water and nutrients, are in the top 8 inches of soil. That isn’t an exact number as roots vary by species and soil conditions. Feeder roots will eventually extend beyond the drip line. For a newly planted tree or shrub, conventional wisdom is to give one inch of water weekly. For sandy soils, you may need to up that to twice weekly. And when temps are over 85 F. another inch weekly is advised. If you wish, use a trowel to dig down 2 inches. If the soil is dry at that point, it is time to water. How much is an inch? A 5 foot by 5 foot area takes 16 gallons to reach one inch. Use a sprinkler or wrap a soaker hose around the tree several times to cover the entire area under the drip line. Sink a pet food or tuna can in the ground and time how long the water runs before hitting the one inch mark. As temperatures cool, trees lose less water. Continue to water as needed all the way through fall. A tree or shrub that is dehydrated going into winter is susceptible to winter kill. Most water is lost through leaves but dry winter winds take moisture out of branches, too. As you watch your new plantings, you will see just how the leaves look and behave and you will learn to catch early signs of water stress. Visible wilting is a late sign and should be avoided. https://www.gardeningknowhow.com/ornamental/trees/tgen/watering-newly-planted-tree.htm