Photo by John Nelson Dr. John Nelson

This plant truly loves the morning.

You can see this species anywhere in the eastern US, from PA to FL, over to TX and into the Midwestern states and Latin America. It is frequently seen on field margins, roadsides, and in ditches. It seems to like sandy places.

This is a native American species and a member of the largely tropical spiderwort family, a family which has given us plenty of showy ornamental plants…and weeds.

Our mystery plant has about 100 or so close relatives in the same genus. This one is a perennial, and it comes up from a cluster of thick roots. The stems are a bit fleshy and jointed, somewhat erect. The plants will form patches. The leaves are elongated and sharp– pointed, each one forming a thin, tight sheath around the stem.

Photo by John Nelson Up to a dozen or so flowers are produced inside a protective, boat–shaped bract, but within this bract only one flower will open at a time. Each open flower has two large, flamboyant petals that are sky–blue. A small, white, inconspicuous third petal is found below and between the blue ones. Six stamens are present, and in these flowers the three upper ones are sterile, not producing pollen, but probably useful in attracting pollinators, often bees.

The plants in sufficient numbers are spectacular when in bloom. Truly, each flower has its moment only in the morning sun, for by the hot afternoon, the flowers have shriveled up to nothing to be replaced the next morning by new, fresh ones.

The arrangement and appearance of the three petals has attracted plenty of attention from botanists. Indeed, Carl Linnaeus, the father of plant taxonomy, was quite taken by these flowers. He likened the two upper petals, as conspicuous as they are, to two prominent Dutch botanists of the 17th century, who worked in Amsterdam. These two botanists, Johannes and Caspar Commelijn, were commemorated by Linnaeus when the plant’s genus’ name was created. And the pale, unassuming, white petal? Tradition has it that there was a third member of the Commelijn family, but that evidently, Linnaeus didn't think he was much of a botanist.

Answer to last week’s mystery plant

Sargasso weed, Sea holly, Sargassum natans

Dr. John Nelson is the curator of the USC Herbarium.

To learn more about the Herbarium, call him at

777-8196. His department also offers free plant identification.

www.herbarium.org