Native Plants

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Tuesday - July 01, 2008

From: Huntsville, AL
Region: Southeast
Topic: Trees
Title: Effects of concrete patio poured around tulip poplar tree
Answered by: Barbara Medford

QUESTION:

We have a beautiful tulip poplar tree in our back yard that we wanted to be the focal point of our patio. We had seen pictures of patios with trees incorporated in patios leaving two to three feet of soil around the trunk. After a friend saw what we had done she informed us the tree might die even though we left a green space around the trunk. What can we do to prevent this from happening now that we have already poured the patio?

ANSWER:

Oops, you just joined the "leap before you look" club, which has a large membership. Preventing damage to the tree would have included not pouring the patio around it. You should never trust pictures you see in home or garden magazines as a guide for your landscaping decisions. The tree you saw may have been a very small tree, or a bush trained into a tree. The patio around it, in fact, may have been open-slatted wood. Or it may have just been a mistake.

Liriodendron tulipifera (tuliptree) is a native of North America, and if you follow the link to the webpage on this tree in our Native Plant Database, you will see a note, down near the bottom of the page, which says: "Tulip tree is insect and disease free. It is intolerant of compacted soil and should not be placed in confined beds or planters near pavement. It grows very rapidly in deep, rich well-drained soils with uniform rainfall. Dry summer weather causes physiological problems. Tulip tree drops its foliage in response to drought and is somewhat weak-wooded."

Tree roots develop and survive where there is adequate oxygen and moisture. Most active tree roots are in the top 3 feet of soil; the majority are in the top 12 inches. The more compacted or poorly drained the soil, the closer the roots are to the soil surface. Roots normally grow outward to about 3 times the branch spread. This tree can grow up to 150 ft. tall, with proportional width, so you can imagine how far how the roots are going to be going, even when the tree is still very young. So, what's going to happen? Well, the tree is not going to do well, but it has a strong will to survive. So, those roots (remember, the most active ones are in the top 12 inches of the soil), are going to keep pushing up, hunting oxygen and moisture. And the patio concrete will start to crack. You can always leave it, and let them fight it out. However, when and if you get ready to sell your house, a back garden centered by a crumbling cement slab and a drooping, perhaps dying tree, is not going to add to the sales appeal.