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?

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
Not Yet Rated

Tuesday - September 27, 2011

From: Rockville, MD
Region: Mid-Atlantic
Topic: Invasive Plants, Propagation, Seeds and Seeding, Trees
Title: Eliminating black locust volunteers in Rockville MD
Answered by: Barbara Medford

QUESTION:

I am a landscape designer whose client has a very large, mature black locust in her front yard. Not surprisingly, she also has multitudes of black locust volunteers popping up all over her yard. The large tree will stay, but how can we safely remove the volunteers and discourage any more of them from coming up? For what it's worth, the tree is native to our area. Thanks for your help!

ANSWER:

From our webpage (which see) on Robinia pseudoacacia (Black locust):

"Because this species is well-adapted to establishment in very poor soil, it has been widely used for land reclamation projects. The eagerness of Robinia pseudoacacia to establish just about anywhere has a dark side; Black locust is often considered an invasive species and a garden thug because it spreads very rapidly by root sprouts and by the copious seeds it produces."

This tree is a member of the Fabaceae, or pea, family with the characteristic long seed pods. The sprouts seen are probably a combination of seedlings and root sprouts. You are correct, it is native to Maryland, as well as the other 48 states and large portions of Canada, as seen in this USDA Plant Profile map on the locations of the plant. Another excerpt from our webpage:

"Its wood, renowned for its toughness, belies its habit of shedding branches in high winds. Finally, its thorns are vicious to anyone attempting to work in or around the tree. This species and its various cultivars and hybrids should be rejected for most landscape uses because of the trees many bad habits."

Your client probably inherited the tree from a previous owner, or it was accidentally planted by birds or other animals, so we won't lecture too much on investigating any plant for its nativity or invasiveness before planting. Our first suggestion, which may not be too practical, is to get the tree out of there, make sure all the leaves and seedpods are raked up and removed from the property, and the roots ground out.

As for preventing further sprouts, here's the plan: Patience and Persistence.

Step 1. Careful policing of the area around the tree and immediate removal of the seed pods comes first.

Step 2. Clipping the root sprouts as far down in the soil as possible.

Step 3. Repeat Steps 1 and 2.

Herbicides, as we are sure you know, are going to be ineffective on root sprouts; the sprouts themselves may brown, but the roots from which they spring are unaffected because they are sheltered by the earth. Sprays would easily float on the wind, killing things you did not intend to die, contaminating the soil and doing virtually nothing to the offending tree.

We have been inundated, during the terrible drought in Texas, with questions about live oak sprouts. This is not quite the same thing because live oaks are excellent landscape and shade trees, and widely cultivated in Central Texas. However, they seem to be much worse in setting root sprouts this year because of the stresses the weather has put on the trees. The sprouts coming out of the roots (and those roots go waaay out, beyond the dripline of the tree) constitute mini branches with leaves on them. This is the tree's survival plan, providing itself with more leaves to produce nutrition for the tree. That's the reason we recommend stump grinding when an invasive tree has been removed, because as long as those roots are in the ground and can put up sprouts, that tree is still alive, not what you had in mind.

One last plug-Mr. Smarty Plants says the best way to control invasive plants is to never plant them, and investigate any tree thoroughly before planting.

Pictures of thorns on locusts

 

From the Image Gallery


Black locust
Robinia pseudoacacia

Black locust
Robinia pseudoacacia

More Invasive Plants Questions

Removing St. Augustine from flower beds
January 25, 2009 - We just had new landscaping put in at our house. We had planting beds prepped and mulched and had Zoysia sod installed outside the beds. The yard before had small areas of St. Augustine growing and no...
view the full question and answer

Cleaning up neglected yard after construction in Austin
October 07, 2009 - We have just finished an extreme makeover on the inside of our house, but all the heavy equipment in the yard left us needing a complete makeover of the outside. The property was previously neglected...
view the full question and answer

How to get rid of devils club (Oplopanax horridus)
November 22, 2007 - please tell me how to get rid of devils club!!!
view the full question and answer

Inadvisability of importing plants from one region to another
March 03, 2006 - I wonder if you could help me. I want to send my friends some conifer trees from England to Florida USA. I went on the Department of Agriculture site and they recommended your site for questions. Than...
view the full question and answer

Native plants threatened by invasives in Oklahoma?
September 28, 2010 - What are some native plants in Oklahoma that are being threatened by invasive species?
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | JOBS | SITEMAP | STAFF INTRANET
© 2016 Lady Bird Johnson Wildflower Center