by Scott Meister, Natural Resources
Cooler nights and shorter days signal a change for many plants. Although colorful blooms are long gone for many species, plants are still using stored energy for one last hoorah to ensure their species’ presence next season: seed production.
In the science world, plants reproduce using what’s called an “r-strategy.” Without the ability to provide parental care, r-strategists produce many offspring in the hopes that a few will grow and survive. (Insects are another example of r-strategists.) For instance, one oak tree can produce 10,000 acorns in a good year, but the majority won’t survive to become trees. Acorns and other seeds are often eaten by wildlife or accidentally destroyed. Some simply do not find a suitable location to grow and thrive.
Plants have different tactics to disperse their seeds in hopes of finding good growing conditions. Milkweed seeds are attached to cottonlike puffs that can sail in the wind long distances. Cattails use water to float their seeds downstream to find homes. When seedpods of wild geranium dry and crack open they launch their seeds like a catapult.
Another common dispersal strategy relies on animals to move a plant’s seeds. (Anyone who has walked off-trail this time of year is familiar with this sly tactic.) Technically, seed dispersal via fur or feather is called “epizoochory.” Epizoochorus seeds, or “sticky seeds” as I call them, are equipped with hooks, barbs or spines that cling to any passing bird, furry mammal (deer, coyote, cottontail, etc.) or pant leg.
Once a seed is attached, the unsuspecting host can transport it long distances. The hitchhiking seed is released when the animal grooms or scratches itself or rubs against an object (or when a person picks the seed off clothes). If lucky, the dropped seed will land in a hospitable location where it can grow the following year.
In DuPage County, dozens of plants rely on wildlife (and humans) to disburse their seeds. The following are a handful of common ones forest preserve visitors might find attached to pants, shirts and pet fur when visiting in fall.
Stickseed is a native plant that grows in woodlands and along wooded trails. It’s inconspicuous eighth-inch-wide summer flowers produce small seeded fruits covered in hooked, Velcro-like prickles, which should leave no question as to how the plant received its common name. The fruits latch to any passing animal or human. Because the plant can be 2 to 4 feet tall, its seeds are likely to stick to shirttails and dogs.
Native common beggar’s tick blooms in late summer in sunny, wet habitats. If you brush against vegetation near a body of water, expect to encounter beggar’s ticks. Each seed ends with two pointed barbs that resemble Batman’s cowl and easily attach to passers-by. In addition to dispersing with the help of wildlife, the seeds are light enough to be carried by the wind, allowing them to grow in many areas. The plants are 1 to 3 feet tall, so the seeds often stick to pant legs and shoelaces.