Native Pollinators

Most people don't relish the thought of inviting more bees into their garden, but pollinators play an important role in our ecosystems. I've just finished reading a new book called "Attracting Native Pollinators: Protecting North America's Bees and Butterflies".

Silphium connatum
Photo courtesy of Mary Tucker

Many folks know that pollinators are more than just bees and butterflies.  Pollinators include wasps, flies, beetles, even birds and bats.  Bees, however, are the best pollinators thanks to unique physical characteristics and nutritional needs.  Recent news stories about Colony Collapse Disorder have made even more people aware of how honey bees are used around the country to pollinate food crops through the transportation of hives in large trucks (timed to arrive as crops enter their flowering phase).  Honey bees, however, are not native bees.  There are hundreds of species of native bees that do a far better job of pollinating flowers than honey bees.  We need to support them.

Non-native honey bee approaches Quince flower

This book's goal is to educate folks on how to both attract and support native bees.  The concepts provided, however, apply also to attracting and supporting non-native bees and other insect pollinators.  The book includes an overview of each type of insect pollinator, including how effective they are in pollination (and why) and what living arrangements support them.  Understanding these details is important to any efforts we make to support them.

Dandelion

Of course it is important to understand why pollination is important, not just for food crops but all plants.  While some plants are capable of self-fertilization, many more need help with pollination or they can have a greater rate of fertilization and produce more vigorous offspring when cross-pollination occurs.  Plants that are endangered or which have reduced populations are especially sensitive to pollination problems: reduced pollination rates means fewer viable seeds and that ultimately affects the size of the population.  Even for plants that can self-pollinate, reductions in cross-pollination means less genetic diversity in the population as a whole.  While wind can help distribute some lighter weight pollens, it is insects that provide most of the "outcross" pollen that plants receive.

Bees: there are three things to understand about native bees - they can be solitary or social, they can nest in the ground or in a cavity, and that they are usually generalists when it comes to the plants from which they gather nectar and pollen.  Most people think of honey bee hives when they think of bee "living arrangements", but more than 90% of the 4,000 species of bees in North America lead solitary lives; this means that each female builds and stocks her own nest without any help.  Bumble bees are the best known native bees that live in a social arrangement.  In this arrangement, each bee has a specific job to do.  Of all the insect pollinators, bees are the most important group for two reasons: bees visit flowers specifically to gather nectar and pollen as food for their young and in doing so transfer large amounts of pollen to other flowers; bees are physically capable of transporting more pollen because of their individual body hairs and other pollen transportation features (we've all seen those big pollen globs on their legs, right?).

Wasps: it was fascinating to learn more about wasps.  Wasps, unlike bees, are carnivores during the larval stage, feeding on insect prey provided by their mothers.  Adult wasps visit flowers only to sip nectar for themselves, and most do not collect pollen on purpose; any pollen collected is by accident.  Pollination is largely incidental as a result their search for nectar (they also sup on soda and other sugary sources, remember?) and far less effective than pollination by bees.

Flies: as the largest group of insects (nearly 120,000 species worldwide), flies represent a significant portion of the insects that visit flowers.  However, like wasps, flies are only visiting flowers to grab some quick energy (nectar), and pollination is usually a by-product.  There are some flies that mimic the look of bees and wasps to elude those that would eat them.  Once way to distinguish a fly from a bee is to look at the number of wings: flies have two wings and bees have four. Flies are good pollinators for some food crops like strawberries and carrots; muscid flies have been commercially raised for carrot pollination purposes.

Butterflies and Moths: I think this statement from the book perfectly describes our relationship with these pollinators: "Although butterflies are not the most important pollinators of plants, they are among the most conspicuous."  Like wasps and flies, butterflies go to flowers only to sip nectar and therefore any pollination is only accomplished if they happen to pick up some pollen on their wings and spread it to the next flower.  I found an interesting tidbit on distinguishing butterflies from moths in this book: butterflies have a small bulbous tip at the end of their antennae.  Moths do not have this bulb.

Beetles: it is estimated that beetles predate bees by 50 million years (according to fossil records); therefore, beetles have been pollinating the earliest flowers (think Magnolia-like flowers) for a long time.  And if you thought there were a lot of flies, consider that there are 340,000 species of beetles worldwide!  Not all beetles visit flowers, and like the other insects except for bees, the purpose of their visit is only to nourish the adult.  In the case of beetles, it is to eat pollen, not sip nectar.

So now that we know we have all these pollinators, how can we help them?  In some cases, the answer is to be a bit more laissez-faire - leave the leaves on the ground to nourish ground dwelling critters like adult beetles and those that consume those creatures like wasps.  Leave dead tree snags and branches for wood burrowing insects like beetles and solitary bees. Brush piles and rocks help as well.  Leave some bare ground for ground-dwelling bees and wasps, and create special mason houses for bees that prefer those.

Plum (Prunus sp.)

Stokesia laevis with Asclepias tuberosa
Photo courtesy of Mike Strickland

You can have fun too; here is the fun part:  plant appropriate plants.  Here is a report on a project partially funded by the Georgia Native Plant Society; the project was a two-year study using Stokesia laevis to attract native pollinators.  When choosing plants: in general, you want to choose regionally appropriate and native plants that are long blooming, have overlapping bloom times, and have nectar-rich flowers.  Also plant butterly-host plants (including woody trees and shrubs) to sustain the larvae of butterflies and moths.  There are plenty of resources on the web about butterfly host plants for your area.  If you want to see the top 20 list of host plants for the mid-Atlantic area (both woody and herbaceous), check out this list provided by Doug Tallamy.

Helianthus sp.

Viburnum nudum var. cassinoides

This book is very helpful in understanding the importance of pollinators and how they live in the world around us.  I learned a lot and certainly plan to implement some changes in my garden to help these guys.  This book is published by The Xerces Society and is available on Amazon.  It includes 34 pages of identification pictures for native bees.  The reference section on pollinator plants is a bit skimpy - one would need to do more research to come up with more regional choices.  In general, look for pollen and nectar-rich flowers like the Helianthus and Viburnum pictured above.

These are unopened flower buds on my blueberry bushes (Vaccinium sp.).  The bees were circling them in the bright sunshine yesterday.  There was no doubt they knew that the buds would be open soon and were anxious to be there when it happened.  How wonderful that we help each other at the same time - they get what they need and I get more blueberries!