Filaree
Also known as redstem filaree, common stork's-bill or pinweed
Scientific name:
Erodium cicutarium
Filaree is a native to the Mediterranean.
It was introduced to North America in the eighteenth century.
Since then it has become invasive over much of the United States.
The way the seeds propagate is quite unique.
Seed launch is accomplished using a spring mechanism. The spring power comes from the
shape changes as the fruits dry. The spiral shape of the awn changes
during daily changes in humidity. This act like a coiled spring
(the awn is a slender, bristlelike appendage on the seeds ).
These changes in the awn due to humidity changes allows the seeds to self-burial once they are on the ground.
The two tasks (springy launch and self-burial) are accomplished with the
same tissue (the awn), which is hygroscopically
active, that is, it warps upon wetting. (from Wikipedia)