Common stork’s bill seed planting itself. Photo: p. roullard
The seeds of the common stork’s bill (Erodium cicutarium), a sticky, hairy annual weed closely related to geraniums (Geranium) and pelargoniums (Pelargonium), sow themselves.
The seeds are launched abruptly into the air by a springlike mechanism, landing up to 3 feet (1 m) from the mother plant. Since they also bear feathery parachutes, they can travel even further on a windy day. But what is really interesting is what they do when they land.
In the video, you see the awn both uncoil as it pushes the seed into the soil, then coil and uncoil several times as it adjusts the seed depth. Video: p. roullard
Each seed bears a long bristle called an awn. It is spiral-shaped and begins to curl into a tight springlike shape in response to dry air. As the air becomes moister, it does the opposite, uncoiling. As it does so, the action drills the seed into the ground, effectively sowing it. If the seed isn’t sown deep enough, the awn will twist up yet again in dry weather, then do some more drilling when the air moistens, repeating the action several times if needed.
A seed that sows itself? How neat is that!