Rent Shop Volunteer Join

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

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

QUESTION:

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.

ANSWER:

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

Tree with blue berries in Los Angeles, CA
March 22, 2016 - There's a tree outside my house with somewhat thin and short spiky leaves with blue berries. The berries Some of the berries have a frost look and some are dark blue.
view the full question and answer

Plant identification of shrub with thorns and purple flowers
July 05, 2011 - I have a small tree or shrub, it has very small or thin thorns on the branches. It blooms in April / May. The flowers are purple. My mother-in-law said that it has been around for over 100 years, b...
view the full question and answer

Invasive spreading weed in Michigan that looks like a small pine tree
July 29, 2013 - I have an invasive spreading weed in my gardens. It has black root system, comes up looking like a small pine tree. The green breaks off when you try to pull it.
view the full question and answer

Identification of flower that looks like Callirhoe in NC
June 12, 2012 - Have a flower similar to callirhoe, but the blossum is fuchia, not purple and the foliage is light sage in color and fuzzy. It is very invasive. What is it? If you have an email address, I can send...
view the full question and answer

Carolina allspice (Calycanthus floridus) in Jasper TX
October 27, 2011 - Carolina allspice (calycanthus floridus) grows in my yard in East Texas. It is native to the eastern U.S., but I notice there is a variety whose distribution extends through Louisiana. Since I live in...
view the full question and answer

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