The Incredible Lightness of Gaura

Lindheimer’s Beeblossom (Gaura lindheimeri) ~ Galveston State Park

One of the prettiest plants still blooming on the late October prairie was the Texas and Louisiana native known as Lindheimer’s Gaura, or Lindheimer’s Beeblossom. Often achieving a height of four or five feet, its loose sprays of flowers give the plant an especially airy appearance; the tendency of the flowers to sway and hover in the breeze have led to yet other names, like butterfly Gaura or whirling butterflies.

Its flowers, which open a few at a time from pinkish buds, are visited by long-tongued bees and bumblebees, as well as by butterflies.The genus name Gaura, derived from the Greek word gauros, or ‘superb,’ refers to the flowers. The specific epithet honors Ferdinand Jacob Lindheimer (1801-1879), an extraordinary early Texan now known as the father of Texas botany.

The plant’s narrow, lance-shaped leaves can be tinged with red throughout the year, but autumn increases their color, making the leaves as appealing as the flowers.

In the early 2000s, taxonomic research led to Lindheimer’s Beeblossom and other Gaura species being moved into the genus Oenothera. Today, the plant is known formally as Oenothera lindheimeri, although that name has not been adopted in the horticultural industry. Both the Royal Botanic Gardens at Kew and the Missouri Botanic Gardens still list Gaura lindheimeri as a valid name. 

Frustrating as such changes can be, one indication that the change was warranted is visible even to those without access to an electron microscope or knowledge of DNA analysis.

When Lindheimer’s Gaura is compared to other Oenothera species such as the Pink Evening Primrose, the Beach Evening Primrose, and Sundrops, one obvious similarity is the flower’s stigma.

Beach evening primrose ~ Oenothera drummondii

Oenothera stigmas are divided into four branches which form the shape of an ‘X’ — easily seen in the shadow on the Beach Evening Primrose above. Whichever scientific name is used for Lindheimer’s Gaura, one thing is certain: ‘X’ marks the genus.

The X-shaped stigma of Lindheimer’s Gaura

 

Comments always are welcome.

 

When Nature Comes With Strings Attached

Pollen strands of a pink evening primrose ~ Oenothera speciosa
Bayou Bend State Park

The Oenothera genus contains about 125 species of flowering plants; pink evening primrose, beach evening primrose, and sundrops are especially common in Texas. Their flowers open primarily in the evening, and are pollinated by a variety of bees and moths.

Because the pollen grains of these flowers are loosely linked by threads of a substance called viscin, only bees with specialized pollen-transporting hairs can gather their pollen effectively. Viscin, a clear, tasteless, sticky substance not only holds the pollen grains together, it also helps attach the pollen to visiting insects.

Some botanists theorize the plants evolved in this way to allow the pollen to stick onto insects that aren’t necessarily designed to carry pollen—especially nearly hairless creatures such as beetles. Other plants in the Onagraceae also have viscin threads, although some—like those found in Fireweed (Epilobium angustifolium) — can only be seen with  magnification.

Pollen strands of a beach evening primrose ~ Oenothera drummondii
Galveston Island dunes

Beyond the viscous pollen strings Oenothera species have developed to aid their pollination, at least one of their kind has evolved another trick for tempting insects to stop by. Scientists have found that Oenothera drummondii, the pretty beach evening primrose, can increase the sugar content of its nectar within three minutes of its flowers being vibrated by visiting bees.

How the scientists figured that out I can’t say, but its very improbability makes me smile. It seems some flowers actively invite bees to drop by for a sip of nectar, as well as a little packet of pollen to go.

Comments always are welcome.