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

More on preventing suckers on live oaks in Austin
August 01, 2010 - I just received an oak sprout answer id=6021. I have a followup question. Our sprouts are caused by the motte we live in - 12 live oaks on 1/4 acre. I understand we will have to hand dig 1000s of t...
view the full question and answer

Fruit crops to grow in Tennessee mountains
May 27, 2013 - My property has a lot of rock formations throughout it and has hundreds of cedars where it is not pasture. I am wanting to grow fruit trees and berry bushes but don't know what can grow in this e...
view the full question and answer

Problems with Cedar Elm in Austin, TX.
August 04, 2012 - Our Cedar Elm has yellowing very dry leaves and something is eating the topmost leaves leaving holes and obviously chewed off leaf segments. Could this be two different things? Aphids and bacteria or ...
view the full question and answer

Color year round, welcome to Austin Texas.
December 04, 2011 - I am new to Austin and want to plant colorful flowers for fall and winter that get a "wow" reaction. I have not seen much at the local nurseries. Any and all suggestions are greatly appreciated!
view the full question and answer

Thoughts on non-native Italian Cypress in Austin
January 01, 2014 - I would like to know your thoughts on growing Italian Cypress trees in Austin Texas? We are looking to create a privacy screen(and prepared to pay more for mature trees to cut down the wait to grow...
view the full question and answer

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