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?

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
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
3 ratings

Saturday - October 25, 2008

From: Austin, TX
Region: Southwest
Topic: Invasive Plants, Non-Natives
Title: Getting rid of giant ragweed in Austin
Answered by: Barbara Medford

QUESTION:

How can I get rid of a large field of giant ragweed? Part of the site is a steep slope, which is difficult to mow. I want to encourage native grasses but they are crowded out by the ragweed.

ANSWER:

The best information we could get on Ambrosia trifida var. texana (Texan great ragweed) after doing some research is to allow perennial plants to crowd out this annual. Yeah, right.

So, here's the plan. Get them before they go to seed. And really get them-either cut off the seeding part or pull out the whole things. They're blooming now (thus all the allergies all over town), and once they've bloomed, they set seed. Birds love the rich, oily seeds for winter food, so you're going to make some birds unhappy, but if you don't want a fresh field of new Giant Ragweed next year, those plants have got to go before the seeds ripen. This is not to say they won't come back, because the birds are going to pick up seeds in the field next to yours, and deposit them for you. But if you can slow it down to the point that you recognize them when they're young and yank them out then, long before they even produce the flowers and pollen and sneezes, then you're at least gaining. 

Most of the native grasses you are interested in are, indeed, perennials and will, given half a chance, begin to dominate the area, but the ragweed, although annual, is just so numerous that it can shade out the perennial grasses and seriously damage their growth. So, there you have it - you're going to have to do it the hard way, and mid-October is a real good time to start. If you wait until they die back in cold weather, they will have already deposited millions of seeds in the ground, and be all ready to go next year.


Ambrosia trifida var. texana

Ambrosia trifida var. texana

Ambrosia trifida var. texana

Ambrosia trifida var. texana

 

 

More Non-Natives Questions

Suckers on non-native crape myrtle in Bay Point CA
July 22, 2010 - How can I stop suckers on a Crepe Myrtle tree? I have bought sucker stopper in the past, but find it hard to locate now. Is there something else I can spray or paint on the base of the tree to stop ...
view the full question and answer

Sad Germanders in Johnson City Texas
September 16, 2011 - I have some grey bush germanders that never seem to do well although they did at first when I planted them four years ago. They have sun and dappled shade on the south side of the house. A friend in ...
view the full question and answer

Yellowing leaves on non-native weeping birch in Brick NJ
August 16, 2009 - I have a young weeping birch-planted in spring-we water regularly, it gets good sun-and rain has been perfect--the leaves get yellow--and now they are a lot! Whats the matter? I love my little tree.I ...
view the full question and answer

Non-native peanutbutter tree suckering in Oregon City OR
August 02, 2011 - I have a beautiful 'peanutbutter tree' in my yard. I have noted that there are plantlets coming up that appear to be attached to the main root(s) of the tree. I have been breaking them off as I don...
view the full question and answer

Non-native, invasive mimosa trees
July 15, 2006 - I have a mimosa tree. The blooms on mine are very pale while I see many other trees with bright blooms. Is there anyway to change the color of the blooms? For instance, is the color due to the PH o...
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP
© 2014 Lady Bird Johnson Wildflower Center