March 23, 2026
Davis Mountain Mock Vervain (Glandularia wrightii)
This is a photo of the two flowers I sketched for my final painting.
The specimen on the left shows the upper part of the flower, the “limb” where 5 petals flair out from the throat ringed by fine hairs. The throat leads to the lower part of the flower – the floral tube (5 fused pale green petals). . Both upper and lower petals make up the flower’s corolla. Below the floral tube are 5 red tipped green sepals (collectively called a calyx) all fused into a cup shape. The specimen on the right is a dissected flower; 2 upper petals are removed, and the floral tube has been opened to reveal the reproductive parts. On the left side are 2 of the female parts of the pistil (pale green style supporting the 2-lobed stigma of the pistil; the ovary was not exposed). Two of the four stamens (male) lie in the mid- to upper right side of the opened floral tube; look for the bright yellow anthers, each sitting atop their own filament
Here’s Another Curiosity to Ponder: I wondered why this plant has 5 petals and 5 sepals but doesn’t also have 5 stamens, which is usually the norm in so many other 5-merous plant species??? Here’s what I learned:
Davis Mountain Mock Vervain (Glandularia wrightii) exhibits a common evolutionary trait in the Vervain (Verbenaceae) family where the flower displays a 5-lobed calyx of fused sepals, and 5 5-lobed petals which fuse into a tube (the corolla). This trait, commonly described as 5-merous, curiously has a reduced the number of functional stamens to four.
This reduction is due to an evolutionary transition from a 5-stamen ancestor. According to literature, the four fertile stamens I observed in my specimens are properly arranged in two pairs (didynamous), both neatly hidden in the floral tube beneath a ring of fine hairs. Also properly so, the filaments (the stalks that support the anthers) of the stamens are fused to the inside of the tube, and not easily teased free.
So apparently, many, many, many, many, Many hundreds of years ago, plants in the Vervain family “decided” having a 5th stamen was unnecessary. “We can do just fine without it, thank you.” Thru the process of evolution, that expendable #5 was ever so slowly reduced to a tiny non-functional structure (referred to as a staminode in modern botanical lingo), or was completely and totally lost, becoming only a memory.
Believe me, this species is an energetic producer of leaves, flowers and seeds. In my experience, Davis Mountain Mock Vervain seems to explode in masses of pink and purple flowers throughout spring, summer and fall, and can last thru winters that don’t freeze. It’s easy to understand why the species has no need of a 5th fertile stamen. Once the plant becomes established, it keeps growing and flowering and spreading, often to the detriment of other desirable plants. If it wasn’t so gorgeous at the height of bloom, it might be considered a weed!
But I’m reminded of the definition of a “Weed ….. a plant out of place.” So yes, you’ll find me actively weeding actively growing Davis Mountain Mock Vervain so my other native plants have a chance at life too!!
Thanks for stopping by!
a curious nature 