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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.

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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.

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Friday - March 23, 2012

From: Fort Worth, TX
Region: Southwest
Topic: Invasive Plants, Non-Natives, Plant Identification
Title: Identity of the mass fields of yellow flowers in North Texas
Answered by: Nan Hampton

QUESTION:

Are the mass fields of yellow flowers we are seeing in north Texas now likely to be Indian Mustard (brassica juncea) or Charlock (brassica kaber or sinapis arvensis)? We are teaching a wildflower idenification class at a community college and are ourselves confused about this identification. Thanks for the help.

ANSWER:

The mass fields of yellow flowers we are seeing around Austin are the invasive non-native Rapistrum rugosum (Bastard cabbage).  See the USDA distribution map (if you click on the map, it will give you an enlarged map with county names).

Brassica juncea (Indian or brown mustard) (see the USDA distribution map) and Sinapis arvensis [syn. Brassica kaber](charlock mustard) (see the USDA distribution map) are certainly possibilities, however, around your area near Fort Worth.

Here are photos for Brassica juncea from Stephen F. Austin University, photos of Sinapis arvensis in FlowersInIsrael.com and photos of Rapistrum rugosum from Biological Sciences, University of Texas.

Here are the descriptions for the three species in Flora of North America as seen on eFloras.org:

Brassica juncea

Rapistrum rugosum

Sinapis arvensis

You can also find descriptions of the three species in "Shinners and Mahler's Illuststrated Flora of North Central Texas" on pp. 459, 476 and 479.

If the photos and descriptions don't help you determine which of these you are seeing, you might consider contacting someone knowledgeable about the flora of your area—for instance, a member of the North Central Chapter of the Native Plant Society of Texas (NPSOT)—to see if they know the identity of these flowers.

 

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