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Saturday - July 30, 2011

From: Evanston, IL
Region: Midwest
Topic: Trees
Title: Planting annuals around young oak in Evanston IL
Answered by: Barbara Medford

QUESTION:

is it OK to plant annuals (i.e. salvias, impatiens or dusty millers) around the base of a young oak tree (2-3 years old)?

ANSWER:

Sure, it's okay, but you need to remember that the health of your oak tree is your first consideration, as it is much more valuable than annual plants. First of all, don't do your planting too close to the trunk of the tree-a couple feet out in all directions would be about right. We assume you are planning to put in bedding plants; be careful digging them in because you don't want to destroy any tree roots. You might want to mulch the plants to help hold moisture in and, as it decomposes, it will add organic matter to the soil. Do not get the mulch up against the tree trunk, this will encourage insects and fungi.

We gave you the good news, here is the bad news. Oaks are not happy to have competition in their territory. Your annuals will probably be all right for a while, because oaks develop this dislike for competition as they get older and larger. Just about everyone knows you can't plant anything under a black walnut tree, because the tree emits juglones, which are substances that damage other plants around the tree. Oak trees don't do juglones, but they are capable of allelopathy, and the substance they emit can be in the soil, the roots, the bark or the fallen leaves. If the plants you put in refuse to prosper, we would recommend planting somewhere else. If you continue to fight the tree's animosity for competition, you will just be wasting resources, and could even damage the tree in the process.

And, of course, as the tree grows larger, you need to consider the shade. Very few blooming plants will bloom well in shade. The bigger the tree, the more shade.

 

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