The flowers are of two types; One, in short terminal branches, produces only pollen.

Some produce little useful pollen of their own, even though they set well if fertilised by another tree.

So a cold, snowless winter will produce low pollen, he explains.

Grasses usually produce pollen during the late spring and summer.

When the flower's job of producing pollen is done, the blossom begins to cool.

These produce pollen every year, and lots of it.

Female shrubs never produce pollen and are the ones you want to look for.

No individual plant of the population produces both pollen and ovules.

The fragrant flowers do not have nectar, but produce pollen.

So the pine tree has to produce pollen in gigantic quantities.