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
Not Yet Rated

Wednesday - January 30, 2008

From: Carrollton, TX
Region: Southwest
Topic: Plant Identification
Title: Identification of plant, possibly giant ragweed (Ambrosia trifida)
Answered by: Nan Hampton and Joe Marcus


I am trying to identify a weed that was prevalant where I grew up in North Central Texas. It grows in low spots and along creeks. It has woody stalks with short spines, grows 3'- 6' tall, the leaves are braod and spiny also, and when you break the stalk, it bleeds red sap. It grows in huge clumps and will take over a creek bank.


The plant that best fits your description is Ambrosia trifida (great ragweed) or, more precisely, Ambrosia trifida var. texana (Texan great ragweed). It grows in waste places and, although native, it is considered invasive in some areas. One of its common names is blood ragweed and the description in Shinners & Mahler's Illustrated Flora of North Central Texas, p. 310, for Ambrosia trifida L. var. texana reads:

"...sap blood red.. . The sap stains the hands red if the tissues are damaged."

Here are additional photos of Ambrosia trifida (giant ragweed) from the University of Texas "Image Archive of Central Texas Plants" and still more photos from the Freckmann Herbarium, Universtiy of Wisconsin.

Ambrosia trifida var. texana

Ambrosia trifida var. texana

Ambrosia trifida var. texana



More Plant Identification Questions

Plant identification
March 15, 2012 - There's a wildflower I can't identify. I have a picture of it and have searched many sites and can't seem to find it. Is there a way I can submit the pic to you to identify?
view the full question and answer

Plant ID from Chicago
August 18, 2010 - This plant is VERY common along highways across the entire midwest, and often other parts of the country. It has a long stem with a cluster of white flowers usually only on the top of the stem. The le...
view the full question and answer

Difference between invasive Chinese and Japanese wisterias and native wisteria
September 12, 2014 - Dear Mr or Ms Smarty Plants, Is there any way I can tell for sure if my wisteria is native? I bought it at a place when it was in bloom that sold a lot of native plants. I Would like to know for sure...
view the full question and answer

Books for plant identification of native California species
March 14, 2008 - When I was going to college, many years ago, there was a field book for plant identification for California native species. I am trying to find that book again or at least a good pocket book on plant...
view the full question and answer

Identity of white flowers, 6 petals and 5 yellow stamens
June 16, 2012 - Have white flower with 6 petals and 5 yellow stamen in middle . Looks like yellow stamen star cluster. Could be Gladious or Star of bethleham but Star has 6 yellow stamen in middle right? Can you id...
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.
© 2015 Lady Bird Johnson Wildflower Center