Flying Seeds

 

Goat's Beard (Tragopogon dubius) head with many fruits. 

These flying fruits disperse seeds over long distances.  

Rowan County, North Carolina. 

 

Plants disperse their seeds in many ways. Seed dispersal is vital for plants to colonize new areas and so new plants are not in direct competition with their parent.  In flowering plants, the seed is part of the fruit, and the main function of the fruit is dispersal of seeds. Some seeds are wrapped in a tasty fruit and are carried away by animals and deposited in new locations.  Other fruits are hitchhikers that cling to the fur of animals or the bootlaces of unsuspecting hikers.  Still others have buoyant fruits and float away on ocean currents.  And some fruits fly.  

Fruits of Box Elder (Acer negundo). Like all
maples, Box Elder makes winged fruits called samaras. 
Rowan County, North Carolina. 

A single samara of Box Elder.  The seed is at 
the bottom and the wing is at the top of the picture.
Rowan County, North Carolina. 

Slow-motion video of Red Maple (Acer rubrum) flying samaras.

Rowan County, North Carolina. 

Flying seeds have two main strategies for dispersal, wings or parachutes.  Maples (Acer sp.) make a fruit called a samara with the seed at the end of a single, asymmetrical wing. When the fruit falls from a maple tree it helicopters down and on a breezy day it can travel long distances.  The wings of maple samaras are airfoils like those of airplanes.  The wing shape produces lift and allows the seed to remain aloft for a long time.

Winged seed of Loblolly Pine (Pinus taeda).
Rowan County, North Carolina. 

Pines (Pinus sp.) do not make fruits since they are Gymnosperms.  Gymnosperms have naked seeds borne on cones and are not part of fruits.  Pine seeds are very similar in appearance to maple fruits and fly in a similar manner.  Ash trees (Fraxinus sp.) also make samaras.  Ash fruits have a seed and an airfoil wing and they too are good flyers.  Long distance dispersal means these trees are often the first to colonize new open areas.  

Samaras of American Ash (Fraxinus americana).
Rowan County, North Carolina. 

Close-up of an American Ash samara.
Rowan County, North Carolina. 

Parachute fruits are made by some members of the sunflower family, the Asteraceae.  The best known of these is the Common Dandelion (Taraxicum officinale).  Everyone has picked a fruiting head of Dandelion and blown the fruits into the wind.  Dandelions are natives of Eurasia and have spread themselves across North America by means of these flying seeds.  Another member of the sunflower family that makes these flying fruits is Goat’s Beard (Tragopogon dubius).  This introduction from Europe is much taller than the Common Dandelion and makes large fruiting heads with abundant flying seeds.  The fruits of both these plants are called achenes.  They have the seed at the bottom, a stalk called the beak and fine cellulose fibers at the top, the pappus.  The pappus acts as the parachute and allows the fruit to travel long distances. 

Fruiting head of Common Dandelion (Taraxicum officinale).  Each achene
is made up of a seed, beak and pappus.
Rowan County, North Carolina.

 

Close up of a Common Dandelion achene.  The seed is at the bottom,
the pappus is at the top and they are connected by the beak.  
Rowan County, North Carolina. 

Bull Thistle (Cirsium vulgare) is yet another Asteraceae with parachuting fruits.  Bull Thistle grows to several feet in height, has spiky leaves and makes purple flowers.  Unlike Common Dandelion, Bull Thistle fruits lack a beak but fly just as well. 

Bull Thistle (Cirsium vulgare) leaves.
Rowan County, North Carolina.

Bull Thistle flower.
Rowan County, North Carolina.

Bull Thistle achene being released from a fruiting head.
Rowan County, North Carolina. 

Video of Bull Thistle achenes flying from a mature flower.

Rowan County, North Carolina.

On windy spring days the air can be filled with flying maple samaras or a summer walk through a meadow can bring clouds of parachute borne seeds of Dandelions.  All these seeds are trying for the same thing.  A fresh start for the plant in a new place.