Take an old plastic mineral bottle and cut 3 slots to make a flap.

Do this another 3 times around the bottle.

Bend the flaps outwards equal distances.

Place the bottle on a garden cane so that it spins freely.

Place the cane in the ground above your plants.

When the wind blows the bottle will spin round.

 

For a better effect, paint the bottle in brightly coloured stripes.