Growing Green: pollinators
Pollination is the transfer of pollen from the anthers of a flower to the stigma of the same flower or another flower. The result is the production of fertile seeds.
When the pollen transfer happens within the same flower, it is called self-pollination. When it occurs between different flowers, it is cross-pollination.
Cross-pollination is preferable to self-pollination because it produces more genetic diversity in plant populations. Genetic diversity plays an important role in the adaptability and survivability of a species.
Some plants have very lightweight, smooth pollen that is easily blown by the wind from one plant to another. Many other plants, however, have heavy, sticky pollen that must be physically picked up from one plant and moved to a different plant. Who does the work of moving pollen? Various animals can do this task, but insects do most of the work of moving pollen. Bees are the most important movers of pollen, assisted by flies, beetles, wasps, butterflies, and moths.
Plants work hard to attract their pollinators and offer them rewards. They offer pollen, an important source of protein, and nectar, a concentrated sugar solution, to lure insect pollinators. The different flower shapes, color patterns, and scents are all part of the plant’s efforts to attract pollinators. Pollinators are also responsible for many of the fruits, vegetables, and nuts that provide vital nutrition for our families. Without pollinators we wouldn’t have abundant blueberries, apples, tomatoes, and squash, to name just a few. Even coffee and chocolate would be less plentiful without pollinators.
Pollinators are in trouble. Beekeepers have been losing an average of 40 percent of their managed European honeybee colonies every year, compared to a 10 percent historic loss.
Declines in other insect pollinator species, such as native bees, flies, butterflies, and beetles, have not been as closely tracked, but recent surveys have shown disturbing population declines and even local extinctions of select pollinator species across Europe and the United States. The cause of pollinator decline is complicated because of the interaction of many different stressors.
Pollinators face many challenges. The conversion of natural habitats to cropland or suburban development fragments pollinator habitat and diminishes the availability of floral resources. Nesting sites are often limited in our urban, suburban, and agricultural landscapes.
Non-native invasive plants that have escaped from our yards further degrade natural habitat by reducing plant diversity. Diseases, parasites, and a changing climate all contribute to pollinator decline.
Exposure to pesticides is also part of the equation. Certain pesticides can kill pollinators outright. Other pesticides can have sublethal effects, impairing a bee’s memory and ability to return to their hive or suppressing the bee’s immune system so they are more susceptible to diseases and pesticides. Pesticides in this category include some neonicotinoids used in systemic pesticides. Because these are poured on the root system and taken up by the plant, homeowners may feel they are safe for pollinators without realizing that the pesticide moves through all parts of the plants, including into the pollen and nectar.
Pollinators are hungry. Our lawns, landscapes, and agricultural crops that replace forests and fields often have little to offer a hungry pollinator. Just like people, pollinators need a diverse diet to thrive. Without good nutrition, all the other stressors are even more devastating. That’s good news to home gardeners who want to help our pollinator friends. Plant more and better flowers. Our yards and gardens can be a major part of the pollinator solution if we plant a diversity of trees, shrubs, and perennials with different shapes, colors, and bloom times.
“Growing Green” is contributed by Lehigh County Extension Office Staff and Master Gardeners. Lehigh County Extension Office, 610-391-9840; Northampton County Extension Office, 610-813-6613.