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Saturday - June 07, 2014

From: Fort Worth, TX
Region: Southwest
Topic: Planting, Problem Plants, Shrubs, Trees
Title: Need for smaller tree with less invasive roots from Ft. Worth TX
Answered by: Barbara Medford

QUESTION:

The sycamore in the front yard has developed roots larger than the branches. They have decided that the water and sewer lines are perfect to acquire their water from. For this reason it will be coming down in fall. Is there a smaller ornamental tree that will not encroach on the buried lines or the house foundation?

ANSWER:

This is an ongoing problem for gardeners. In hot Texas, everyone longs for shade and big-leaved, relatively fast-growing sycamores sound like a blessing UNTIL the roots start messing up underground equipment. You have made a wise decision to take down your Platanus occidentalis (American sycamore), which, by the way, according to this USDA Plant Profile Map, is native to the Tarrrant County area.

Our general advice on roots is that the roots of a tree will extend out at least 2 to 3 times farther than the dripline or shade line of the tree. Our experience is that roots can be very invasive, often above the soil surface, and interfering with hardscape such as sidewalks, patios and, yes, house foundations, not to mention water and sewer lines. If you follow the plant link Platanus occidentalis (American sycamore) to our webpage on the tree, you will find these statements:

"The American sycamore is a wide-canopied, deciduous tree, 75-100 ft. tall, with a massive trunk and open crown of huge, crooked branches."

"A shade tree, Sycamore grows to a larger trunk diameter than any other native hardwood. The present champions trunk is about 11 feet (3.4 m) in diameter; an earlier giant was nearly 15 feet (4.6 m)."

So, imagine 2 to 3 times that much root material below the ground and your underground lines don't stand a chance. In a large field or open landscape, it would be lovely. In a small city lawn it is a nightmare. Many of our visitors trying to avoid this sort of problem ask us for "taproot" trees, operating under the impressions that a taproot goes only straight down and does not interfere with other hardscape. Here is a previous Mr. Smarty Plants answer with respect for selections of taprooted trees. That answer is from Denison TX, in Grayson County not far from Tarrant County, so the suggestions made should still apply. However, please note this paragraph from that answer:

"Once the tree is planted and begins to mature, the distinctions between the root types become less pronounced. Then, the depth and lateralness of the roots is greatly dependent on the soil condition. Highly compacted soils, soils with low oxygen content and soils where the water table is near the surface are not likely to produce a strong tap root. Their roots are more likely to be lateral and located very near the surface with the majority of the roots located in the top 12 inches of soil. Also, it is important to realize that the spread of the roots can be at least 2 to 4 times greater than the drip line of the branches.

So, bottom line, you may need to not only modify the size of replacement plant for your sycamore, but perhaps the type. There are shrubs that will have less intrusive roots and provide greenery and bloom in your garden, but not shade. It's a hard choice, but what's it going to be? Sewer lines or shade? Here are some shrubs from our Recommended Species for North Central Texas list:

Anisacanthus quadrifidus var. wrightii (Flame acanthus)

Callicarpa americana (American beautyberry)

Ilex vomitoria (Yaupon)

Mahonia swaseyi (Texas barberry)

Salvia greggii (Autumn sage)