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Friday - November 12, 2010

From: Houston, TX
Region: Southwest
Topic: Compost and Mulch, Planting, Herbs/Forbs, Trees
Title: Trees for cutout in driveway in Houston
Answered by: Barbara Medford


I live in central Houston. I have a new driveway with a cutout of 4' x 8'. I would like to plant a shade tree that will not break up the concrete. What do you recommend?


This is not the first time a similar question has been asked. Here is an excerpt from previous answer on planting trees for shade in or near a driveway:

Our advice is, don't do it. To have hope of being successful planting a tree, it would have to be quite small and still could have transplant shock. The site you describe, bounded by a driveway all around, is also risky. Any tree's roots are going to extend as much as 3 times the drip or shade line of the tree. Either the driveway, curbing and the street beyond it is going to hurt the roots, or the roots are going to push up and crack the concrete. They just don't co-exist well. You might have to wait 10 years for a tree to get up tall enough to create significant shade, by which time your driveway will probably be crumbling. But, to us, the most compelling argument against deliberately planting trees over a parking area is the mess. It doesn't much matter which tree it is, or what time of year, something is always dropping. Surely you have seen the cars with what looks like green fur on them driving around Houston? And where have they been? Why, parking under an oak which has been dropping its lovely allergenic green blossoms. And how about aphids getting in the trees? Then you have that charming aphid by-product, honeydew, making a sticky mess on your car. If you plant a fast-growing tree that doesn't take the time to develop a very strong structure, a windstorm or snow (which we now know can happen in Houston) could drop a branch on a car parked there. Leaves, seeds, acorns, bugs, twigs and branches-we love trees, too, but they make lousy carports.

Since you have already poured the concrete, and we assume it has already dried, let us suggest that you forget about shade, and make an attractive perennial and shrub bed there. Smaller shrubs will not have the large root structure that a tree would, and some are evergreen and/or have nice blooms or berries. You will need to build up the bed with compost and possibly some topsoil, as the soil where the driveway is probably is not prime. The compost will also help with drainage; very few plants will tolerate their roots standing in water for an extended time. In Houston, where it rains more than it does here in Austin, you are going to have the problem of an impermeable surface (the concrete driveway) that will funnel the water into the nearest hole, that is, your mini-garden. A raised bed will both permit drainage to be more normal, while the composted soil will absorb and use the water more efficiently. Another concern is going to be the heat. On a concrete driveway in an August sun, there is going to be lots of heat being reflected onto those plants.

You need to select sun-loving native plants that are well adapted to Texas heat. Furthermore, you will need to be able to irrigate the area when the rain does not fall. We are going to go to our Recommended Species section, click on East Texas on the map, and search for herbaceous blooming plants and shrubs in the database that meet the criteria above. We are going to specify full sun, which we consider to be 6 or more hours of sun a day, but not the soil moisture. You can use the same technique to make your own plant selections. Follow each plant link to our webpage on that plant for information about projected size, sun and water needs, color, time of bloom, etc.

Herbaceous blooming plants for mid-driveway garden in Houston:

Achillea millefolium (Common yarrow)

Asclepias tuberosa (Butterflyweed)

Coreopsis lanceolata (Lanceleaf coreopsis)

Echinacea purpurea (Eastern purple coneflower)

Ipomopsis rubra (Standing cypress)

Lobelia cardinalis (Cardinal flower)

Salvia coccinea (Scarlet sage)

Salvia farinacea (Mealy blue sage)

Shrubs for mid-driveway garden in Houston:

Callicarpa americana (American beautyberry)

Hydrangea quercifolia (Oakleaf hydrangea)

Ilex vomitoria (Yaupon)

Morella cerifera (Wax myrtle)

From our Native Plant Image Gallery:

Achillea millefolium

Asclepias tuberosa

Coreopsis lanceolata

Echinacea purpurea

Ipomopsis rubra

Lobelia cardinalis

Salvia coccinea

Salvia farinacea

Callicarpa americana

Hydrangea quercifolia

Ilex vomitoria

Morella cerifera




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