Native Plants

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Monday - April 30, 2012

From: Austin, TX
Region: Southwest
Topic: Pruning, Herbs/Forbs
Title: Trimming of penstemon after bloooming from Austin
Answered by: Barbara Medford

QUESTION:

I planted a penstemon in my backyard last fall and it's doing great. Once the flowers have bloomed, do I cut the stalk back? It is about 2 ft tall and doesn't appear to be doing anything. I believe I have a ruellia humilis.

ANSWER:

When we searched on our Native Plant Database on the genus Penstemon, we found 120 species; we switched to penstemons native to Texas and still got 26. So, we went to the Wildflower Center Master Taxa List, which lists all the plants on the Wildflower Center grounds. We figured we're in Austin, you're in Austin, the plants must be pretty similar, at least. The only Penstemon listed as growing on the grounds is Penstemon cobaea (Wild foxglove), so you can follow the plant link and learn more about the plant.

The answer to your question is yes, you can cut back the bloom stalks after they finish blooming. It's tidier looking, and the new growth emerges from the roots in the Spring.

What we don't know is what the reference to Ruellia humilis (Fringeleaf wild petunia) is all about. That is a whole different genus. We will admit there are some similarities in the flowers. You might also follow that plant link and see if you can figure out which is which.

From the Image Gallery

Prairie penstemon
Penstemon cobaea

Prairie petunia
Ruellia humilis