What is seed dispersal?
Seed dispersal is the movement or transport of seeds away from the parent plant.
What are the benefits of plants dispersing their seeds?
Plants need to disperse their seeds away from the parent plant to stop overcrowding and to create new colonies or groups of that species. The seed survival is often (although not always) higher away from the parent plant. This may be due to competition for water, light and the nutrients to help them to survive. Predators often target the high concentration of seeds beneath an adult plant so if the seeds are spread away from the parent plant they have more chance to grow into healthy adult plants. Seed dispersal also allows the plants to reach habitats that are in an area that is best for the plant to survive in, and colonise new habitats nearby and even completely new areas altogether. This is very important to maintain species diversity and ensure the survival of the plant.
How do plants disperse or spread their seeds?
Plants have limited mobility. They don't have legs so rely on various other ways of spreading their seeds! This is how they do it:
Wind
Some seeds are adapted to catch the wind. These seeds have stiff wings covering the seed and these 'wings' are twisted and balanced so the seed spins around by the wind. They are light in weight and are easily blown away. The sycamore tree has these type of wings. Often called 'helicopters' these have parachutes that catch the wind. The ash also has winged seeds.
Other plants have very light, soft, fluffy seeds like the dandelion, willow herb and bulrush that are float away in the wind.
Poppies also use the wind to spread their seeds. The head of the poppy have little holes all around the top rather like a pepper pot and when the wind shakes the plant the tiny seeds are thrown out of the shaker through these holes.
Bursting
There are fruits and plants that burst open and throw their seeds in all directions away from ythe parent plant. Some plants such as peas, beans and laburnum have pods that when the pods become overfull they burst by force a bit like blowing up a balloon until it bursts. Gorse uses the sun on hot days to burst and spread its seeds and geraniums also rely on the heat of the sun. Himalayan balsam is a plant where the heads of the flowers that contain the seeds are often burst by children as they make a great popping sound!! There is also a fungi called a puffball that is round and bursts to disperse the spores.
Water
Some fruits and seeds are waterproof and can float. The most well known is the coconut but what about British plants? Himalayan balsam, mentioned above, is often seen on the banks of rivers and streams. When the flower head burst, the seeds fall into the water. This is one way that this plant successfully spreads. Water carries the seed along by its current and eventually will be forced on to the bank of the river or stream and there it can establish itself and begin to grow. Foxglove and harebell often grow next to streams and use the same method to spread their seeds.
Catching a lift
Some fruit have hooks or spines on them and these catch on to the fur of passing animals as they brush against the plant. Burdock has prickly cases and sea holly has spines that also use this method. Common cleavers is sticky and sticks to anything it comes into contact wit. Also loved by children who like to stick on to each others clothes!
Drop and Roll
These are fruit that drop of the tree and split open where they land on the ground. Horse chestnut trees spill their conkers on to the ground and also fruits like cherry that have a stone. When the fruit rots the stone is exposed and will germinate in the right conditions.
Fire
Not usually thought of in terms of seed dispersal but still important for releasing seed or breaking seed dormancy of some species that would otherwise not be able to be released or germinate without fire. The Erica species such as heather and some pine species rely on the burning of the outer part of the seed to release the important part that will germinate and grow.
Animal Food
Many fruits are very tasty to animals and birds such as blackberries, apples and gooseberries. When an animal or bird eats these fruits, the little seeds are not digested and pass through them unharmed and surrounded by a fertiliser that helps them grow. Animals that are particularly useful to aid this seed dispersal are bats, squirrels, cattle and deer.
Another way that seeds are spread are through animals such as squirrels that will collect nuts and acorns for winter, bury them and then will often forget where they are.
Insects such as ants too will collect seed for food back to their nests where it may germinate or may be dropped on route and it starts to grow.
Humans
We too have a role to play in seed dispersal. We often discard old apple cores or other fruit when we have finished eating it by throwing it away in the countryside. We also purposely buy and grow seeds in our garden. After all, our gardens or window boxes are still habitats!
Although not seeds, willow can have small branches or twigs cut off it and planted in the ground and it will grow.
Seed dispersal is the movement or transport of seeds away from the parent plant.
What are the benefits of plants dispersing their seeds?
Plants need to disperse their seeds away from the parent plant to stop overcrowding and to create new colonies or groups of that species. The seed survival is often (although not always) higher away from the parent plant. This may be due to competition for water, light and the nutrients to help them to survive. Predators often target the high concentration of seeds beneath an adult plant so if the seeds are spread away from the parent plant they have more chance to grow into healthy adult plants. Seed dispersal also allows the plants to reach habitats that are in an area that is best for the plant to survive in, and colonise new habitats nearby and even completely new areas altogether. This is very important to maintain species diversity and ensure the survival of the plant.
How do plants disperse or spread their seeds?
Plants have limited mobility. They don't have legs so rely on various other ways of spreading their seeds! This is how they do it:
Wind
Some seeds are adapted to catch the wind. These seeds have stiff wings covering the seed and these 'wings' are twisted and balanced so the seed spins around by the wind. They are light in weight and are easily blown away. The sycamore tree has these type of wings. Often called 'helicopters' these have parachutes that catch the wind. The ash also has winged seeds.
Other plants have very light, soft, fluffy seeds like the dandelion, willow herb and bulrush that are float away in the wind.
Poppies also use the wind to spread their seeds. The head of the poppy have little holes all around the top rather like a pepper pot and when the wind shakes the plant the tiny seeds are thrown out of the shaker through these holes.
Bursting
There are fruits and plants that burst open and throw their seeds in all directions away from ythe parent plant. Some plants such as peas, beans and laburnum have pods that when the pods become overfull they burst by force a bit like blowing up a balloon until it bursts. Gorse uses the sun on hot days to burst and spread its seeds and geraniums also rely on the heat of the sun. Himalayan balsam is a plant where the heads of the flowers that contain the seeds are often burst by children as they make a great popping sound!! There is also a fungi called a puffball that is round and bursts to disperse the spores.
Water
Some fruits and seeds are waterproof and can float. The most well known is the coconut but what about British plants? Himalayan balsam, mentioned above, is often seen on the banks of rivers and streams. When the flower head burst, the seeds fall into the water. This is one way that this plant successfully spreads. Water carries the seed along by its current and eventually will be forced on to the bank of the river or stream and there it can establish itself and begin to grow. Foxglove and harebell often grow next to streams and use the same method to spread their seeds.
Catching a lift
Some fruit have hooks or spines on them and these catch on to the fur of passing animals as they brush against the plant. Burdock has prickly cases and sea holly has spines that also use this method. Common cleavers is sticky and sticks to anything it comes into contact wit. Also loved by children who like to stick on to each others clothes!
Drop and Roll
These are fruit that drop of the tree and split open where they land on the ground. Horse chestnut trees spill their conkers on to the ground and also fruits like cherry that have a stone. When the fruit rots the stone is exposed and will germinate in the right conditions.
Fire
Not usually thought of in terms of seed dispersal but still important for releasing seed or breaking seed dormancy of some species that would otherwise not be able to be released or germinate without fire. The Erica species such as heather and some pine species rely on the burning of the outer part of the seed to release the important part that will germinate and grow.
Animal Food
Many fruits are very tasty to animals and birds such as blackberries, apples and gooseberries. When an animal or bird eats these fruits, the little seeds are not digested and pass through them unharmed and surrounded by a fertiliser that helps them grow. Animals that are particularly useful to aid this seed dispersal are bats, squirrels, cattle and deer.
Another way that seeds are spread are through animals such as squirrels that will collect nuts and acorns for winter, bury them and then will often forget where they are.
Insects such as ants too will collect seed for food back to their nests where it may germinate or may be dropped on route and it starts to grow.
Humans
We too have a role to play in seed dispersal. We often discard old apple cores or other fruit when we have finished eating it by throwing it away in the countryside. We also purposely buy and grow seeds in our garden. After all, our gardens or window boxes are still habitats!
Although not seeds, willow can have small branches or twigs cut off it and planted in the ground and it will grow.
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