En EspaŅol

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
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
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

Scorched leaves on Red Maple from Lufkin TX
April 30, 2012 - I have a Red Maple that we planted in Lufkin, TX about a month ago and fertilized about 2 weeks ago. We water the tree often. The leaves have become scorched looking on the outside of about 1/3 of t...
view the full question and answer

Florida law on removing orange trees
March 24, 2007 - I live in a co-op mobile home park with a board of directors that tell me that if I have to cut down my orange tree that Florida law says that I have to replace it with another orange tree. I say that...
view the full question and answer

Tahitian gardenias (Gardenia taitensis) salt and wind resistance in Hawaii
February 03, 2006 - Are Tahitian Gardenias salt tolerant? We live on a rocky coastline in Hawaii and we get a lot of salt spray.
view the full question and answer

Are junipers tainting the soil in Loveland CO?
June 10, 2011 - Have several varieties of junipers around my yard. Each year I try to place a small garden in a corner of my yard, the plants don't do well at all. Growing up nearby, I gardened with my parents so ...
view the full question and answer

Transplant shock in Mountain Laurel in San Antonio, TX
June 03, 2011 - I planted a 2 ft. tall Texas mountain laurel a month ago. Some of the leaves have turned very yellow and some of them are falling off. The plant doesn't look real healthy in general. I did add s...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
© 2015 Lady Bird Johnson Wildflower Center