My Backyard Habitat: Plants’ Adaptations For Seed Dispersal
Successful reproduction is crucial for the survival and continuation of any species. For plants, effective seed dispersal is a critical part of that success. Because plants are unable to move, they have evolved some ingenious techniques to ensure that their seeds are dispersed far and wide. Wind and animals are the most widespread and successful means of spreading seeds; however, some plants utilize uniquely different methods.
Wind: Some seeds have wings or parachutes. These are adaptations that help seeds travel further than simply dropping to the ground. The most obvious method is exemplified by the fluffy “parachutes” of dandelions that catch air currents to carry seeds away from the parent plant. Maple tree seeds are winged, allowing them to spin and generate lift. This extended flight reduces competition for resources and enables the trees to colonize new areas.
Animals consume seeds: When animals eat fruits containing seeds, the fleshy part of the fruit is digested, but the seed is preserved due to its hard coating. The seeds pass through the animal’s digestive system and can be deposited far from the original plant. This process also scarifies the seed coating, which aids germination for many plant species. And the nutrient-rich droppings are also an excellent fertilizer. Seed-eaters include many birds, chipmunks, squirrels, and mammals. Our winged friends play a vital role in seed dispersal as they can travel further distances than most animals.
Blue jays and acorns: While other animals cache nuts for winter consumption in the same burrow or tree, blue jays practice scatter-hoarding. One bird can transport up to five acorns at a time in its throat pouch and then bury them miles away. In subsequent trips, a blue jay always brings acorns to a completely different location. A single blue jay hides thousands of acorns each season, so it is no wonder some of the acorns are forgotten. And because the birds only choose healthy and fertile acorns, new oak trees will sprout.
Utilizing ants: Many plants depend on ants to dispense their seeds. These plants have a fat-filled structure on the exterior of their seed called an elaiosome. Ants carry the entire seed to their underground nest. They consume the elaiosome and dispose of seeds in “trash piles,” perfect nurseries for the seeds to develop. Buried in nourishing soil, seeds are protected from slugs and mice. Sixty percent of understory plants in our forests got there thanks to ant activity. These include bloodroot, trillium, and spring beauty.
Explosive seeds: Not all plants wait for wind or animals to scatter their seeds. Jewelweed is famous for its explosive seed dispersal mechanism. As seed pods mature, they build up internal tension. When touched or shaken, they burst open dramatically. The force of this “explosion” flings seeds several meters from the mother plant, ensuring seeds are not crowded in one spot. Dispersal of lupine seeds is similar. As seeds dry out, they split open in a twisting manner that catapults the seeds up to six feet away.
Witch hazel also employs natural ballistics to spread its seeds. As its woody seed capsules dry and mature, they build up so much pressure that when they finally rupture, they forcefully shoot out two glossy black seeds at an amazing speed of 30 feet per second and as far away as 30 feet.
Water movement and hitchhiking: Many coastal, aquatic, and marsh plants rely on water to spread their seeds. These seeds are often buoyant or waterproof, enabling them to stay submerged for long periods of time. Button bush, alders, and willows are spread in this way. And let’s not forget the sticky seeds that cling to clothing or fur of a passerby. Tick trefoil and burdock are examples of hitchhiking seeds.
The next time you observe a plant in a spot you’ve never seen it before, think about how it might have gotten there. Seed dispersion is yet another example of plants’ interactions with their environment and the adaptations that make survival possible.
My Backyard Habitat is published monthly in cooperation with The Newtown Bee by Protect Our Pollinators. For more information or to reach the organization, visit propollinators.org.