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

List of North American plants grown in other countries
August 17, 2008 - I am working on a childrens story and would like to let the teachers who read this book know where some of the native plants in my book grow throughout the world, or if they grow outside of the USA. p...
view the full question and answer

Yellowing leaves on weeping willow
August 03, 2008 - We have a 4 year old Weeping Willow, 12+/- ft. tall and this week the leaves are starting to become yellow. This willow is full and robust in appearance, best it's ever looked. We have 2 other Wee...
view the full question and answer

Decline in non-native crape myrtles
June 15, 2007 - I live in Round Rock and the ground is rocky about one foot beneath the surface. I have about 14 crape myrtles that have been doing very well for about 6 years now. Last year the leaves on 1 started...
view the full question and answer

Mites in soil of house plants
June 25, 2008 - Hi there! I recently noticed tiny silver mites in the soil of my plants that I only notice after watering. These plants are indoors in on a window ledge (a dwarf palm, aloe plant and Hawaiian Scheffle...
view the full question and answer

Tree with taproot for Jodhpur India
July 05, 2013 - I am a resident of India. I need information of a tree with tap roots to grow in my backyard. We have moderate to hot climate here. It needs to be as small as possible due to lack of space. It'd be g...
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