Sunday, August 30, 2009

Planting for Pollinators

The United States is experiencing a severe decline in populations of pollinators, the insects and birds that carry pollen from one plant to another enabling them to reproduce and provide us with an abundance of  foods and plants. This is an environmental issue that is seldom mentioned in newspapers or on television. The value of pollinators is incalculable. The commercial value of the products pollinated by just one pollinator, the honey bee, is said to be $14 billion per year in America, but the real value of pollinators cannot be measured in dollars, for they are essential to the great abundance and diversity of plants that we use, consume and admire, the loss of which would be an unspeakable tragedy.  The good news is, there is something we can do to increase pollinator populations that is both simple and pleasurable: namely to include in our gardens a diversity of plants that produce pollen and nectar, plants that are beautiful as well as useful.
Consider the honeybee, one of our most important pollinator. In 2006 reports appeared in the United States and Europe of large honeybee losses ranging from 50 to 90% of the worker bees in the hive, losses so large that the condition became known as “Colony Collapse Disorder”.  The symptoms were unusual: most of the adult bees had left the hive; there were no dead bees;  there were no signs of predation; brood cells remained capped.  Investigators first looked to known bee predators and pathogens as the possible cause of the disorder such as Varroa mites,Nosema apis and Israeli Acute Paralysis Virus, yet so far a single specific cause has not been found, and many believe that several factors may be involved, an important one of which is poor nutrition, that is, a dearth in the quantity and diversity of blossoms from which bees can obtain pollen and nectar. This scarcity of blossom is due to changes in land use, to the conversion of rural land to monocultures such as corn and soy beans and city land to lawns and golf courses, and to the mowing and chemical treatment of areas alongside roads and highways, making all such areas sterile deserts to honeybees.

Other pollinators are also at risk.  According to the National Academy of Science, wild pollinator populations in the United States are trending downwards.  Populations of butterflies, moths, ants, bats and hummingbirds, have been significantly reduced;   the survival of dozens of wild bee species is in peril; in Minnesota, monarch butterfly populations are down 38%.  Informed persons assert that, as in the case of the honeybee, poor nutrition is a critical factor.  
Our task, though large, is not unpleasant, requiring us as it does to include in our gardens plants that are pleasing to the eye in a variety of colors and shapes.  An article by David Sperling of the Wisconsin Natural Resources Department contains suggestions by the Xerces Society on how to plant to attract pollinators:
Plant a diversity of plants that flower all season; different species of pollinators are active in different times during the period May through October.
Use local native plants; they are four times more likely to attract bees and butterflies than exotics.
Choose several colors of flower of different heights;  native bees are particularly attracted to blue, purple, violet, white and yellow blossoms.
Include flowers of different shapes;  bees have different sizes, body shapes and tongue lengths and choose different shaped flowers.
Plant flowers in large clumps;  clusters of flowers attract more pollinators than individual blossoms.
The following plant genera are good sources of nectar and pollen, and are native to Minnesota:

Aster (Aster)                                    
Milkweed (Asclepias
Beardtongue (Penstemon) 
Beebalm (Monarda)
Blazing star (Liatris) 
Cup plant (Silphium)
Wild indigo (Baptisia)
Fireweed (Chamerion) 
Goldenrod (Solidago) 
Giant hyssop (Agastache) 
Ironweed (Vernonia)

Joe pye weed (Eupatorium) 
Leadplant (Amorpha) 
Lobelia (Lobelia)
 Lupine (Lupinus) 
 Zizia (Golden Alexander)     
          Let some of the following herbs go to flower in your garden to provide for pollinators:

Rosemary (Rosmarinus)
Borage (Borago) 
Catnip (Nepeta) 
Cosmos (Cosmos) 
Lavender (Lavandula)
Oregano (Origanum)
Russian sage (Perovskia) 
Spearmint (Mentha)Squill (Scilla) 
Basil (Ocimum)

 The Xerces Society is an international non-profit organization that advocates for invertebrates and their habitats.  One of its core programs focuses on native pollinators.  See

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