How much water for a transplanted arborvitae tree?

Asked June 14, 2015, 7:53 AM EDT

We have a hedge of three arborvitae trees, planted a year ago. The center one died, and we have replaced it, carefully following all the instructions for replanting the tree. It's about 6.5 feet tall. We know the best time to transplant is the fall, but we had no choice because the original tree was not going to survive. We would like to know how to water it so that it remains healthy, particularly since it is so hot right now. We don't want to over water, but we want to make sure it takes hold and can also survive the winter. We have a soaker hose arranged around all the trees, but we would like to know how long to water each day and what process to follow all summer.

Montgomery County Maryland

1 Response

Do not water every day. Think about the natural way plants are watered.

Plants need about 1" of water a week. They like soil that is about as wet as a wrung out sponge. They do not want soggy, saturated water all the time. Too much water can, literally, drown them. (Plants need oxygen around their roots.)

So, a "deep" watering once a week--possibly two times a week when there is no rain and evaporation is high from high temperatures or wind--is the way to water your plants. Of course, if we have a drenching rain, you don't need to water.

The other part of the issue is that rain is scattered, especially when we're getting thunderstorms in summer. There is no way to know how much water your plants are getting unless you have a rain gauge. We recommend that everyone get one. Doesn't have to be fancy. A tin can can work.

You may have to stick you finger into the soil to see if it is damp. You can allow the top 1-2" of soil to dry out inbetween waterings. You cannot water on a schedule. (And we have no idea how much water your hose puts out, so we can't help you with that. If you can to calibrate it, put it in a bucket and run it for a period of time and see how much is in the bucket.)

Generally, when temperatures are cool and precipitation is more regular in fall, winter and spring, the soil stays moist and watering is not necessary. However, occasionally we have a drought in spring or fall--this spring we went 4 weeks without rain. So, you have to be aware of rainfall and be ready to supplement when necessary.

To keep your tree healthy, be sure it is not planted too deeply (no deeper than it was in the container.) Do not mound mulch on the trunk--mulch should never be more than 1-2" and never touch the trunk.)