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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 is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Tuesday - August 22, 2006

From: Leander, TX
Region: Southwest
Topic: Trees
Title: Determining gender of Texas Hill Country native trees
Answered by: Nan Hampton

QUESTION:

How can I identify which (Tx Hill Country) native trees are separate male & female? Specifically Tx Pistache and American Smoke Tree. Do I have to wait until they flower and inspect the flower for certain characteristics? Most helpful would be guidance to a book or article that explains the botanical characteristics, so that I can apply to other species.

ANSWER:

Plants with both male and female flowers on the same plant are said to be monoecious (in the same house). The botanical term for plants that have the female flowers and male flowers on separate plants is dioecious (in two houses). To be even more technical, the plants with only male flowers are said to be androecious and the ones with only female flowers are gynoecious—probably a lot more than you wanted to know!

Both of the trees you asked about, American smoketree (Cotinus obovatus) and Texas pistache (Pistacia mexicana) are dioecious, with their male and female flowers on separate plants. You can discover this by selecting "Characters" from the menu at the top of each plant's page. Unfortunately, not all of our records in the Native Plants Database carry that information. However, there are several print sources that do identify which plants are dioecious. Two of these are Trees, Shrubs, and Vines of the Texas Hill Country by Jan Wrede (Texas A&M University Press, 2005) and Trees of Central Texas by Robert A. Vines (University of Texas Press, 1984). Of the two, the Vines book describes the structure of the male and female flowers in great detail so that you could determine which gender your tree is.

 

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