Rent Shop Volunteer Join

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
See a list of all Smarty Plants questions

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

Need help with plant identification, visit the plant identification page.

 
rate this answer
1 rating

Wednesday - September 30, 2009

From: Houston, TX
Region: Southwest
Topic: Trees
Title: Neighbor's Arizona ash roots in Houston
Answered by: Barbara Medford

QUESTION:

There is a huge Arizona Ash tree in my neighbor's yard. Its trunk is about 27 feet away from the foundation of my house and its foliage reaches my roof. I am planning to dig a trench on my side of the fence (about 15 feet from the trunk) and install a root barrier. How deep is the trench supposed to be? What is the best material for root barrier against Arizona Ash? And, how long should the trench be? Thank you.

ANSWER:

Fraxinus velutina (velvet ash), also called Arizona ash, is native to far West Texas, but not to the Houston area. We really don't think you need to worry about those roots as much as about the branches touching your roof. 

While it is certainly true that tree roots can grow up to three times the spread of a tree, the problem in foundations is soil subsidence. The tree root does its part on this by looking for water and sucking it up, but if the soil is dry, the foundation is probably going to drop and shrink anyway, and that is much more likely to cause the foundation damage then the tree roots. There is really no way to tell a tree to grow in another direction, and the branches against your roof can definitely cause problems. Insects, not to mention squirrels and raccoons, consider tree branches against a house as an open invitation to come in, have a bite to eat, and spend the winter. Certainly a trained arborist could prune the branches away from the house, but when you prune a plant, where does the new growth appear? Right, it appears in the area you pruned. We think your first step would be to confer with your neighbor on trimming his tree branches back away from your property.

In terms of whether or not the roots will harm your foundation, you can read the recommendations from Iowa State University Extension Service for Sidewalks and Trees which bases the distance trees should be planted near pavement or other concrete structures on the mature height of the tree.  Fraxinus velutina (velvet ash) is a small to medium-sized, deciduous shade tree, usually no taller than 40 ft. in cultivation. Their recommendations are:

1. trees with a mature height of less than 30 feet, 3-4 feet from pavement,
2. trees with a mature height of 30 to 50 feet, 5-6 feet from pavement,
3. trees with a mature height of greater than 50 feet, at least 8 feet from pavement.

With a distance between your foundation and the trunk of the tree of 27 ft., and the expected height of the ash tree of 40 ft., which would only require a 5 to 6 ft. distance, it would appear your foundation is safe, even if your roof is not. If you still wish to consider installing some sort of root barrier between the tree and the foundation, here is more information about root barriers.

From our Native Plant Image Gallery:


Fraxinus velutina

 

 

More Trees Questions

Viability of Desert Willow and Hong Kong Orchid Tree in Spring Branch, TX
December 26, 2006 - We live in Spring Branch, Rt 281 north of San Antonio. We want to plant a Regal Desert Willow tree and a Hong Kong Orchid tree. Will the cold / freeze be a problem? Where locally can we purchase th...
view the full question and answer

Affect of poisonous plant roots in soils for vegetables from Rusk TX
May 11, 2013 - I have a huge old flowerbed in front of my house that I want to plant veggies in, but I'm afraid to. It has a catalpa tree there, which I sell the worms from, but the entire tree (bark, leaves, flowe...
view the full question and answer

Large, fast-growing shade tree for Val Verde County, Texas
April 03, 2016 - What is an overall good shade tree, very large & fast growing, to plant in Central South Texas, Val Verde County region? I am told that virtually nothing but Live Oaks or some other type of Oak will ...
view the full question and answer

A tree to replace a pin oak in PA
January 25, 2011 - My 120 yr old pin oak has root and butt rot, 5 of 13 roots dead by pressure testing. I am in Pittsburgh PA. I want to plant a root rot resistant tree, either evergreen, fir or deciduous. The tree is 9...
view the full question and answer

Which is best-Oklahoma Redbud or Texas Redbud in Austin?
March 25, 2010 - I live in Northwest Austin and would like to plant a small redbud tree in my front yard. My yard gets full sun. Which is better - the Texas redbud or the Oklahoma redbud?
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.