pollination

Our theme for March is Gardening for Pollinators. Over the next several weeks we will post six articles written by Extension Master Gardener Volunteer Diane Almond. Diane is also a Master Beekeeper and will be sharing a wealth of information about what gardeners can do to help pollinators. This is the first of her six articles.

It is rare for several days to go by without media coverage on the topic of pollination. While plenty of the coverage is fascinating if not informative, much of it is sensationalized or just plain inaccurate. This month, let’s investigate, and set the record straight. Where better to start than with a definition: What is pollination? In a word: sex, well actually two words: plant sex. Technically, pollination is the transfer of pollen from the male flower parts (anthers) to the female flower part (stigma) of the same plant species. Yes, flowers are the sexual organs of more than a quarter million species of angiosperms, from the giant oak tree to the tiny violet, from corn and camellias to pansies and peppers, from dogwood to daisies.

Sometimes a plant’s flowers are perfect, having both female and male parts, while some species such as cucumber, melon and squash have two different flowers, male or female on the same plant.

The Master Gardener Help Line often gets calls from home gardeners concerned that their squash plants aren’t setting fruit, and that the flowers fall off. A closer look will reveal that those first flowers on the squash plant are male flowers producing pollen; in fact if you check early in the morning you can often find squash bees sleeping in the flowers and then cavorting getting covered in bright orange pollen. Callers are encouraged to notice the flower differences, and to be patient, waiting a week or so for the plant’s female blossoms.

For some species, most notably the hollies, each plant is either male or female. Ever wonder why that large, healthy holly tree which is covered with tiny white blossoms and thousands of foraging bees in spring never makes any berries? It’s a male and all those flowers are producing gobs of protein and lipid rich pollen that bees gather in earnest, and in doing so inadvertently transfer to the flowering female trees in the neighborhood.

 

When pollen is successfully transferred, fertilization occurs and the plant sets seed and bears fruit, thus fulfilling its single purpose: producing the next generation with a slightly different genetic mix.

Animals find their mates by walking, flying, swimming, crawling etc.; flowering plants, rooted and almost immobile, need help from pollinators. Approximately 20% of the species have their pollen distributed by the wind; many of these species are the monocots or grasses which make a huge abundance of very fine, small-grained pollen since the wind is so random in its work. The other 80% generally produce nectar, scents and visual cues to attract and aid animal pollinators, mostly insects and especially bees, in transferring their heavier pollen. We’ll learn about the pollinators next, and about pollinator-friendly gardening.

Written by Diane Almond, Extension Master Gardener Volunteer