A beautiful purple carpet extends across many fields in Kansas each early spring. Growing only a few inches above the ground, these purple Kansas meadows will soon be plowed. More purple patches sprout in our yards, soon to produce seeds before we start mowing grass.

Commonly known as henbit, its scientific name is Lamium amplexicaule. It is not native to North America. Henbit originated in Asia, Europe and northern Africa. It arrived long ago, spreading west into the Great Plains. Henbit is an early spring wildflower, basking in the sunlight after the winter thaw and before tall weeds or trees grow leaves to block the sun. Back in its Mediterranean homeland, henbit even flowers during the mild winters.

The purple flowers consist of four male stamens, two long and two short. The purple carpet we see from a distance is thousands of flowers, each a ring of fused petals forming a tube nearly an inch long. Being among the first flowers in early spring, henbit is an important pollen and nectar source for bees. And if there are not enough pollinating insects, the flowers can self-pollinate.

In either case, henbit has evolved to produce seeds before being overshadowed by other plants. —Or before being plowed under!

And that is the question that should puzzle us. Since many Kansas fields with this beautiful purple henbit will soon be plowed under, how does henbit keep returning year-after-year, carpeting the meadow with color?
The answer: the soil seed bank. Not to be confused with genetic seed banks where botanists store wide varieties of important crops variants, the soil seed bank consists of the varieties of seeds that are mixed in the soil and available to eventually germinate.

It was Charles Darwin who first observed seeds germinate from soil taken from a lake bottom in 1859. Once he pointed out that soils stored seeds, this idea of soil seed banks led to research that explained why some plants would rapidly appear as weeds while other plants were slow to invade.

Some plant seeds are “transient,” germinating at the first opportunity and are present in the soil seed bank for only a short time, or not at all. But “persistent” seeds endure through many opportunities to germinate; the common weed known as lambsquarters produces seeds that remain in the soil seed bank ready to germinate for up to 40 years. And tropical lotus seeds can reside in lake bottoms for over 1,000 years and germinate!

Research on the soil seed bank is important in agriculture; it helps us understand why some weeds are more common than others. And henbit is truly an evasive weed. But because it grows so early in the spring and is plowed or cultivated out so readily that it gives us little trouble in farming, we don’t mind it as a “weed.”

And it is so darn pretty this time of year.