Seeds on the Move

With roots holding firm to the earth, plants are committed homebodies. But like all living things, movement is essential to their survival. This they accomplish by sending their seeds out into the world in creative and astonishing ways.

Seeds ride the wind – think dandelion parachutes and maple keys. Other seeds get swept along by water currents. Some seeds are dispersed by explosive force. When the seed pods of the aptly named touch-me-nots are ripe, they burst on contact, launching their seeds outward.

A great many seeds tap into the mobility of birds and animals to spread themselves around. Nuts are carried off and buried by squirrels, for example.

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Some seeds are contained within burrs equipped with hooks that cling tenaciously to animal fur, or human clothing. A burr that sticks fast to the haunch of wide-ranging mammal like a deer or a bear has the potential to travel several kilometres before being dislodged.

Burrs are freeloaders, offering nothing but irritation to the animals that transport them. But an equally effective way to go places is to play nice. Fruit and berries are delicious and eagerly consumed. The seeds they contain pass through the digestive tract of the birds and animals that eat them. Then, when nature calls, the seeds are deposited, along with a dollop of fertilizer to kick-start their growth.

Wildflower seeds also get mobile by offering tasty rewards. This time ants are the conveyance of choice. Fatty structures called elaiosomes attached to the seeds of bloodroot, trillium, and other wildflowers appeal to those industrious insects.

The ants carry the seeds back to their nests, where the elaiosomes are eaten. The seeds, now snuggly ensconced beneath the ground, are well placed to sprout in the spring.

During the last ice age Ontario was a barren place. We can thank the remarkable mobility of seeds for the verdant landscape we know today.