Fall 2021 Conservationist

Sticky Seeds

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.

Many native species of ticktrefoil grow in DuPage County, but all of them produce seedpods covered in fine, hooked hairs. A member of the legume (or bean) family, ticktrefoil seeds are recognizable as flat bean pods 1 to 3 inches long with two to five segments. Showy ticktrefoil is the most common in DuPage and grows in sunny locations, including along trails. Fortunately, the fine hairs easily detach from clothing.

The scientific name of enchanter’s nightshade, Circaea lutetiana, comes from Circe, an enchantress and goddess in Greek mythology. But the plant can be more maddening than mesmerizing to those who find its seeds attached to clothing. Growing in woodlands and shady areas, one flower stalk can produce a dozen or more tiny flowers, each producing a seedpod with hooked hairs that stiffen in fall, making them stronger and more likely to latch upon someone walking by. Growing 1 to 2 feet tall, the entire flower stem with its multiple seedpods can break from the plant and attach to clothing at knee level or below.

Common burdock is not native to DuPage, but this invasive plant is widely distributed with an ability to grow almost anywhere, including unkept backyards. Its large heart-shaped leaves measure up to 2 feet long. Flower stalks form in summer and can reach 6 feet tall. As a flower withers, a bur with small stiff hooks forms and remains on the plant through winter. (Examining burdock seeds under a microscope in the 1940s inspired a Swiss man to invent Velcro.) The hooks are so numerous that removing them from clothing or pets can be difficult; they’re so strong they can trap light-weight hummingbirds.

Epizoochorus seeds are one of nature’s smart designs, but because some of these “sticky seeds” can become invasive, visitors should always check for unwanted hitchhikers before leaving a forest preserve, inspecting clothes, pets, and shoes — especially shoelaces — and removing seeds before leaving the area. It might add an extra step, but it’s just part of enjoying the forest preserves in fall!