Question

wind pollinated flowers usually grow in clusters. why?

Answer 1

because wind carry a lots of pollen grain along it.

Answer 2

Wind pollinated flowers grow in clusters to increase the chances of pollination.  We know that they are not dependent on pollinators; wind takes the pollen grains along and land at different places. The reason of growing in groups increases the chances of pollination. The process of wind pollination is also called Anemophily.