Seed dispersal mechanisms

Leon is visiting his grandma Ellen. She needs some help with gardening, and Leon was more than happy to help! They are pulling up the weeds, when Leon accidentally touches a plant that shoots out something at him. Oh no, what was that?! The plant sprayed me with something!

Don’t worry Leon, it’s nothing dangerous. The plant you touched is an exploding cucumber. The fruit of it was ripe, so when you touched it, the fruit split open and shot the seeds out. Thanks to that, the seeds can fall to the ground and grow in new places away from the parent plant. It’s a seed dispersal mechanism, called explosive seed dispersal.

But this type of seed dispersal is not the only one, there are several others too! Look at the dandelions in the garden, Leon. The yellow petals have fallen off, and in their place are brown seeds with fluffy, hairy things growing out of them that look a bit like tiny parachutes. When the wind blows, or when you blow on the dandelion Leon, the seeds are blown away. The white “parachutes” help the seeds float away, rather than just fall to the ground immediately.

It’s impossible to tell where the seed will eventually fall to the ground. The seed might be able to grow there or it might not. That’s why dandelions produce so many seeds: so at least some of them can grow into new plants! This type of seed dispersal mechanism is a wind seed dispersal. Another way of spreading seeds in your grandma’s garden Leon, is when the seeds are carried around by animals, or even by you.

If you take a closer look at your trousers, you can see tiny bits of plants sticking out of them! Ouch! They’re spiky... They’re the seeds of the burdock plants. They’re covered in small, spiky hooks that have caught on to your trousers.

If you hadn’t noticed them now, but brushed them off somewhere else, you would have helped the plant disperse its seeds to a new place! Different animals, such as cats or dogs, often get seeds like this stuck in their fur when they move through gardens or parks. In this way, they carry the seeds to new places. There is another way in which animals disperse seeds. Seeds are often hidden inside a sweet smelling, tasty looking fruit!

Animals that eat fruit often can’t digest these seeds: so the seeds come out again in the animals’ droppings! Because animals help disperse seeds, we call this animal seed dispersal. Plants can also spread their seeds by water. One example is coconuts that are very large but can float in water. Coconut trees often grow near water, so when coconuts fall into the water, they can be carried hundreds of kilometres away to places where they may have never grown before.

This type of seed dispersal is water seed dispersal. Why do plants use these different seed dispersal mechanisms? Well, dispersing seeds prevents new plants from all growing in the same place. This way competition for resources such as light, water and minerals, is reduced and the new plants have a greater chance of growing and developing. Just look how many weeds there are all over your grandma’s garden!

They are very good at dispersing their seeds.