Dispersal

Seeds that grow too near to their parent plants, have to compete with the parent plants for food, light and space. Seeds therefore need to be spread away from the parent plant if they are to avoid this competition, and grow into well developed and healthy new plants. 

The spreading around of plant seeds is commonly referred to as dispersal.

Modes of Seed Dispersal:

There are a number of modes or ways by which seeds may be dispersed, these include:

  1. Wind dispersal
  2. Water dispersal
  3. Animal dispersal 
  4. Mechanical dispersal

Scroll through the entire page to view discussions and links on various modes of dispersal, or follow the bookmarks above to get directly to each topic (use the "Back" button to return to the top of the page).

Wind Dispersal:

Plants using the wind to disperse their seeds may exhibit the following characteristics:

  •  Very light seeds which the wind can easily carry, as in many grasses like "Fowl foot" grass.

Fowl foot grass (Eleusine indica) has numerous small light seeds

  •  Seeds covered in feathery materials, that act like parachutes when caught in the wind, as in the Oleander.

Oleander seed with 'parachutes'

  • Seeds that look and act like helicopter rotors, which may spin and fly in the wind, the  Mohogany being a local example.       

 

 

Closed mohogany pod in tree.

 

Mohogany pods open on the tree to release seeds.

Parts of a mohogany pod.

 

 

Mahogany (Swietenia mahagoni) seeds below spiral through the air like helicopter rotors.

 

  • Seeds that flutter or spin in the wind.

Foliage, flower, fruit and seed of the Jacaranda

 

Water Dispersal:

Plants using water to disperse their seeds may exhibit the following characteristics:

Coconut trees (Cocos nucifera) growing near the sea

  • A tendency to grow near the sea or rivers

A young manchineel tree (Hippomane mancinella) growing on the beach

Coconuts have hollow centers and have been known to float hundreds of miles across the sea before rooting successfully

 

  • Seeds or fruit that can float, allowing them to be carried away from the mother plant by water

Manchineel fruit rot to leave buoyant, woody, star shaped pits that float in water

 

Animal Dispersal:

Plants using animals to disperse their fruit may exhibit the following characteristics: 

  • Fleshy edible fruit, where the flesh is consumed and the seed passed out or discarded at another location

Jackfruit fruit in tree

Mammee apples have edible orange flesh and large seed

A cluster of grapefruits

  • Sticky or clinging fruit or seeds which attached themselves to passing animals, to be dislodged at another location

 

"Burr grass" (Cenchrus sp.

 

 

Burr grass fruit may cling to clothing or animal fur. The fruit may then fall off or be removed at another location. Seeds from these fruit may then germinate at the new location, thereby spreading the plant around..  

 

 

 

Burr grass fruit clinging to clothing.

 

 

Mechanical Dispersal:

Mechanical dispersal is sometimes also referred to as self-dispersal.

Plants that use mechanical means to disperse their seeds may exhibit the following characteristics:

  • Fruit that split or shatter suddenly, throwing their seeds away from the mother plant

Sandbox seed capsule

The Sandbox tree disperses its fruit mechanically

Seed capsule ruptures suddenly and releases flat round seeds

River tamarind (Leucaena leucocephela) seedpods

 

Mechanical dispersal is common in many legumes (like peas and beans)

Dry legume seedpods split suddenly along their seams to scatter their seeds

Immature (green), mature (brown), and split river tamarind fruit on tree.