Seed Dispersal: How Plants Get Around

Plants are so widespread in natural places that it’s easy to overlook them. Almost everywhere you go at certain times of year, the plants form a wall of green. But how do plants find their habitats in the first place? After all, they can’t move around on their own like animals. In this Deep Stuff blog post, let’s explore seed dispersal: how plants get their seeds to places where they can grow.

Why do plants need seed dispersal?

Although it might be obvious to botanists and other plant experts, it can be hard to imagine why plants need to “move around”. Just like with animals, there are a whole bunch of reasons:

Finding new habitats where resources like light, water, or nutrients are more abundant
Avoiding predators, parasites, or competitors in crowded areas
Keeping up with changing conditions like warmer climates, floods, or wildfires
To ensure that their offspring can thrive

Habitats for plants can quickly get crowded. Competing for water, space, soil nutrients, or sunlight for photosynthesis can make it hard for young plants to get a good start. Seed dispersal helps young plants colonize newly available habitats.

Like all other living things, plants need to find and stay inside of their habitat. In other words, they need to make sure that they are hanging out in places where they can survive. Specifically, this means places where they can feed themselves, grow, and reproduce. Furthermore, those places need to have conditions that the species can tolerate.

Finding the right habitat

For example, most tropical orchids can’t survive in a dry desert. On the other hand, desert-adapted cacti would quickly die off in a waterlogged marsh. As conditions change in the landscape around them, or as good habitat become crowded, populations of plants need to move into new areas. This ensures that individuals thrive and that populations don’t go extinct.

Different types of plants need very different types of habitats. For example, cattails (*Typha sp.*, left) grow in moist wetland environments. If the wetlands dry up, they may die or be outcompeted by other species. The same goes for ocotillo (*Fouquieria splendens*, right) which thrive in deserts but get outcompeted in wetter habitats. The ability to move seeds around helps plant populations keep up with changes in the landscape and keep a leg up on the competition.

Why seeds?

So if plants need to move around just like animals do, why should seeds do the moving? Well, for starters, adult plants are rooted into the ground. While some, including many invasive species can “move” by spreading suckers or horizontal roots or stalks along the ground, many cannot.

Seeds are small, portable, and don’t have roots. They’re much easier to move than entire plants. Many seeds get moved by animals. When they are moved by ants (above), the process is known as *myrmecochory*.

However, seeds don’t have roots. These baby plants are more or less portable, and almost always much smaller than an adult plant. Seeds are also protected; they often have coatings or shells to keep them safe from predators. That’s the perfect recipe for travel!

When a plant produces seeds, those seeds are its offspring. In other words, you can think of them like a wolf’s pups or a robin‘s eggs. Just like any other parent, plants want to look out for their “babies”. If all of their babies stayed close to home, their habitat would quickly become too crowded. So, seed dispersal helps plan seeds strike out on their own to find good habitat.

How do plants disperse their seeds?

Burdock (*Arctium sp*.) is a common plant that sticks its seeds to animals (and people!) to get them moved around. These seeds use hooks to grab onto fur and fabric and hitch a ride. It was these seeds that inspired the design for velcro!

I’m sure you can see one big problem here: seeds still can’t move on their own! And that’s absolutely true. The key part of that phrase is “on their own”. While plant seeds can’t really move themselves, they are certainly great at getting other things to do the moving for them.

Cattail (*Typha sp.*) seeds are dispersed by wind. To do this, they have fluffy parts that catch the air (known as the *pappus*) and are very small and light.

Here are just a few examples of the many ways seeds get around:

Floating on ocean currents (Coconuts)
Attaching to animal fur or skin (Cockleburrs, Beggar’s ticks, Goosegrass or Bedstraw)
Getting eaten by an animal, then pooped out somewhere else (Berries, like mistletoe)
Flying on the wind (Maple trees, Dandelions)
Exploding under pressure (Witchhazel, Bittercress, )
Burying and hoarding by animals (Oak acorns, some pines)

Seed “dances”

Scientists and naturalists often use technical words to describe these ingenious methods of seed dispersal. For example, moving via animals (by sticking to them or passing through their gut) is endozoochory. Meanwhile, anemochory describes movement aided by wind currents.

Pepole can be great dispersers too! Burdock seeds all over a pair of hiking boots.

The many different kinds of seed dances fall into two categories:

Biotic, which involve living things (mostly animals)
Abiotic, which involve wind, water, or other non-living aspects of the environment

All of these words contain “-chory”, which shares a linguistic root with the word “choreography”. While the ancient Greek word khoreo can mean “to move” or “to spread”, you can think of these methods as seed-dances. Some seeds dance with animals, some seeds dance using gravity. Other seeds dance with the ocean, or the winds. These beautiful dances get them where they need to go.

Coconut palms (Cocos *nucifera*) disperse their gigantic seeds by making them buoyant. They float along ocean currents, able to survive in salt water for long periods of time. Eventually, they may find new beaches to sprout and grow!

Here are some more great names for modes of seed dispersal:

Ballistic – Explosive seed dispersal
Myrmecochory – Dispersal via ants carrying and moving seeds
Dyszoochory – When scatter-hoarding animals like squirrels hide seeds and forget some of them
Hydrochory – Movement via water currents
Chiropterochory – Transport by bats
Barochory – Falling because of gravity
Herpochory – Seed “crawling” by means of little hairs that change position with changes in humidity

Berries are dispersed via *endozoochory*. In other words, they get moved around by animals that eat them, move somewhere else, and poop them out! The fleshy fruit is often digested, but the seeds likely remain intact.

Further listening

If you’d like to learn more about seed dispersal, check out the Nature Guys episode “Seeds on the Move” to hear plant guru Greg Torres‘ take on the subject.

Thanks for reading about seed dispersal!

Do you have a favorite plant-dance? Are you curious about how other plants move their seeds? Let us know in the comments! If you’ve got other topics that you think deserve a deep-dive, shoot me a message using the Contact page. Until next time!