Host an Event Volunteer Join Tickets

Support the plant database you love!

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
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 Invasive Plants Questions

Shade tolerant plants for privacy from Larchmont NY
April 19, 2014 - Love your site! We have a 4'x4'x50' stone wall, full sun, with a planting bed 30"H by 24"D. We're looking for privacy, so a hedge with pruning is needed. We have looked at Ilex Crenata (8'),...
view the full question and answer

Eliminating English Ivy in East Flat Rock NC
April 13, 2010 - In the woods behind our house our neighbor has an invasion of English Ivy. It creeps over and through the fence into our yard, and we want to fight back! I have read the other articles about cutting...
view the full question and answer

Ligustrums planted last summer are doing poorly in Houston, TX.
March 06, 2012 - I planted large mature ligustrums trees (~ 8 ft) last summer and the leaves are turning yellow and falling off. Can you please tell me what the cause of this might be and what we can do to prevent th...
view the full question and answer

Controlling Straggler Daisy
July 07, 2011 - Is there a barrier I can use that will keep Straggler Daisy under control so that I will not be a problem for my neighbors?
view the full question and answer

Smarty Plants on Invasive Plants
June 22, 2004 - What is an invasive plant?
view the full question and answer

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