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September 2019: The Wind and the Wings- Anemochory

Maple in Duckweed

Anemochory is defined as wind-aided seed dispersal. It seems that tapping the wind as a source of energy is not new new idea. In fact, with a few modifications, many plants have found the wind provides a valuable service for both pollination and seed dispersal. Here, we are interested in how some plants rely on the wind to move their seeds. The tumbleweed, a symbol of the American west rolls along distributing its seeds as it travels. Ironically, this plant is also called the Russian thistle (Salsola sp.) which was introduced from Eurasia and is considered a an invasive species. Other seeds have special shapes or attachments that enable them to glide or whirl such as the seeds of maples and pines, where as cottonwoods, willows, milkweeds and thistles use wispy plumes of gossamer threads to float their seeds on air currents while others, such as those released by some orchids, are so small and ultra-light they are more like drifting spores than seeds.

Seeds that can take advantage of the wind are commonly found in open habitats or elevated in tree canopies. Wind-dispersed species often mature in the dry season to take advantage of windy conditions that optimize long-distance dispersal events. Traveling away from the parent tree helps seeds get to locations that may enhance germination success. Depending on the species involved and the method of riding the air, the seeds can be small, lightweight and produced in the millions so they can travel far and wide. It can be amazing to realize that that tiny smaller than pinhead-sized seed that is even difficult to find in the wispy puff that lands at the table may produce a Cottonwood tree whose trunk diameter is too big to be encircled by the joined hands of six people.  

Anemochorous species can be extremely successful at colonizing distant soils which can be vexing during plant restoration efforts when sites are literally overrun with undesirable invasive species like yellow star thistle, undesirable knapweeds, salt cedar and/or dandelion (to name a few). But this same ability also makes sure that beneficial native species find their way to remote habitats that establish populations of cottonwoods and willows in remote desert springs and streams.