En Español

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?


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 - March 25, 2009

From: Austin, TX
Region: Southwest
Topic: Trees
Title: Are hackberries harmful to other trees?
Answered by: Joe Marcus


A neighbor warned me that a hackberry tree that naturally sprouted up recently will harm the roots of other trees nearby and that it is such a bad tree we should take it down before it gets too big. It is surrounded by mostly cedars and an oak. Do you thinks hackberries can do harm and are worthy of removing for that reason?


Every plant that puts down roots in the earth compete in some way with its neighbors; some compete more aggressively than others.  The rhizosphere, that is, the soil where roots grow, can be thought of quite accurately (if not a bit simplistically) as a war zone.  Plants, animals, fungi and microorganisms living within the rhizosphere continually struggle with one another for their share of the resources available there.

Many trees and other plants interfere with their competition through one of a multitude of processes known collectively as allelopathy.  Allelopathy typically involves living or dead and decaying plant parts exuding, volatilizing or leaching chemical compounds that are inhibitory or harmful to nearby plants.

Hackberry trees, Celtis spp. are known to inhibit the growth of competing plants through allelopathic processes.  The mechanism used by hackberries involves the release of a witch's brew of chemicals known as phenolic phytotoxins leaching from fallen, decaying leaves.  The leachates from rotting hackberry leaves have been shown to inhibit the germination of seeds and the development of seedlings.  So yes, hackberry can do harm to nearby plants, though it is unclear if it has any effect at all on established plants such as trees, shrubs or even mature perennials. 

Ashe juniper, which is probably the cedar your mentioned in your question, and oaks are also known to be allelopathic.  Few plant species will thrive beneath the canopy of Ashe juniper.  If there are any sycamores, pecans or walnuts in your garden, they're also waging chemical warfare on one another.  Lest you come to think of these trees as "bad plants," you should know that as time goes on we will certainly come to learn that many, if not all, plants employ chemical defenses (and offenses) in one form or another.

As landscape plants, hackberries are not without other problems.  They're messier than most other trees, tend to be short-lived, are prone to breaking in storms and don't often make particularly handsome specimens.  On the other hand, hackberries are extremely important sources of food for wildlife.  Many birds, mammals and some butterflies depend on hackberries for their survival.

On balance. hackberries definitely play an important role and have a place in nature and maybe even in peripheral areas of your landscape.  They are probably best left out of more prominent parts of your garden, though.



More Trees Questions

Tree that successfully treats psoriasis
January 31, 2009 - Dear Mr. Smarty plants,I have a rather unusual question. Do you know of a tree/plant that you can grow in a container, looks like a conifer/evergreen, is green, has wispy looking branches, but when t...
view the full question and answer

Season to plant Pacific Wax Myrtle from Fallbrook CA
July 25, 2013 - Would like to know which season would be the best to plant Pacific Wax Myrtle in Fallbrook, CA area? I presently have invading bamboo, which I want to get rid of. Thank you!
view the full question and answer

Looking for a plant to use as a windbreak for a small orchard in Pineville LA.
February 28, 2011 - We are looking for a good plant to use as a wind break for our small fruit orchard.
view the full question and answer

Will Texas Mountain Laurel roots damage pipes in Tucson AZ?
May 20, 2010 - We have a Texas Laurel tree in our back yard,and it is doing fine, and we are are planning to put another one in the front yard close to the house will the root system attack our pipes ? no septic sys...
view the full question and answer

Distance from wall to plant Eastern red cedar
September 26, 2008 - I want to plant a row of Eastern red cedar on the high side of a 2 to 2 1/2 ft large Pavestone block retaining wall, preferably as close to the wall as possible. We have put maybe 4-5" of gravel beh...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
© 2016 Lady Bird Johnson Wildflower Center