Powerhouse Pollinator Plants

Dr. Leonard Perry, Horticulture Professor Emeritus
University of Vermont

With declines in bee populations from various causes, reduced monarch butterfly populations, bat population declines, and an increasing awareness of the importance of these pollinators to the food we eat, many gardeners are putting in pollinator gardens or adapting existing landscape to be pollinator-friendly.  This can be as simple as planting a small grouping of a flower, shrub, or tree attractive to pollinators.

Many garden-related organizations are collaborating on this topic through the National Pollinator Garden Network.  Founded in Fall 2014, they aim “to help restore critical pollinator populations in support of the President’s Executive Strategy to Promote the Health of Honey Bees and Other Pollinators.”  Through the Million Pollinator Garden Challenge (millionpollinatorgardens.org), they are trying to register a million public and private gardens and landscapes to support pollinators.  At the Pollinator Partnership website (share.pollinator.org), you can register your garden or planting.

In addition to plants that provide nectar and pollen, you should provide a water source, sunny areas if possible with windbreaks, and minimal or no use of pesticides.  When choosing plants, you should include native plants as they are often best adapted to our native pollinators.  Make sure not to choose invasive species.  Plan for blooms throughout the growing season.  Plant a grouping of several of a particular plant, as groupings are more attractive to pollinators than just one or a few plants.

With all the interest in pollinators, there are an increasing number of research projects on pollinators, as well as resources.  One of the most extensive listings, and information, searchable by region of the country, is from the Xerces Society (www.xerces.org) under their Pollinator Conservation Resource Center web page.  You also can buy their book from Storey Publishing on Attracting Native Pollinators, which covers the pollinators, plants, and considerations for various landscapes and habitats. Another resource that I find useful, filled with facts, lists and photos, is the paperback by Heather Holm, Pollinators of Native Plants.

The Pollinator Partnership website already mentioned (pollinator.org) has extensive plant lists and 24-page leaflets (which you can download as pdf files for free) for each of 34 eco-regions of the United States and Canada.  You can find your region easily by zip code. Each of these leaflets gives information on plant traits, the pollinators you’ll find and support there and what flower features they prefer, plantings and habitats for various locations such as farms and homes, and plant lists with flower bloom times to aid in planning for continuous blooms.

For instance, my part of northern Vermont falls in the Laurentian mixed forest ecological province.  For this region, some of the trees and shrubs the Pollinator Partnership lists for May and June blooms are downy serviceberry (white flowers), chokecherry (white), and American basswood (yellow). A couple of large shrubs for later bloom are the bunchberry dogwood (white) and staghorn sumac (yellow green).  American witchhazel is a shrub with fall blooms (yellow).  Other native trees you might consider for pollinator habitat enhancement, such as serving as larval hosts, are birches, American beech, and both white and red oaks.

Some shrubs recommended for pollinators by the Xerces Society include highbush blueberry (white or pink flowers) and pussy willow (yellow or green) for early bloom.  Among those for mid-season are ninebark (white) and New Jersey tea (white).  For late season consider buttonbush both for flowers (white) and as a larval host.

Black locust is a good example of a native plant that bees love, is gorgeous in bloom, and that you may find recommended, but that also may be invasive outside of its native range.  Found growing naturally in parts of the southeastern states, it is planted and found naturalized in most other states.  Particularly in several northeastern and Midwest states, and along the west coast, it is considered by many as invasive—displacing native vegetation.  This particularly is a problem in prairies and savannas.

For perennials in this Laurentian province, the Pollinator Partnership lists a couple dozen.  Really early, when little else is out, is the marsh marigold (yellow), particularly adapted as its name indicates to wet areas.  Other early perennials are the wild sweet William phlox (pink to lavender), wild geranium (pink), and the Canada white violet (white with streaking).  For late spring and early summer, choices include red columbine (red and yellow), harebell (blue), water avens (purplish red), blue flag iris (blue purple), narrow-leaf blue-eyed grass (blue purple), red trillium (red), and golden zizia (yellow).

For summer, perennial choices for pollinators include turtlehead (white), flat-topped aster (white and yellow), Joe-pye (lavender pink) and boneset (white), swamp milkweed (pink), wild bergamot (lavender pink to violet blue), beardstongue (white), obedient plant (pale to dark pink), cardinal flower (red), and the common native black-eyed Susan (yellow, dark brown center).

For late blooms, choices include the calico aster (white and pink), New England aster (purple), and goldenrods (yellow).  In a Delaware study by author and entomologist Doug Tallamy on best bets to attract moths and butterflies (www.bringingnaturehome.net), goldenrod attracted the most species (115) with asters a close second (112).

In another study, this one at the University of Vermont, graduate student Annie White has collected data on the attractiveness of native species to pollinators, compared to cultivar selections of these species (“nativars”).  Of the 13 pairs of plants she compared, seven of the native cultivars attracted significantly fewer bee pollinators than the species. These were  ‘Strawberry Seduction’ yarrow, ‘Corbett’ columbine, ‘Twilite Prairie Blues’ baptisia, three coneflower cultivars (‘Sunrise Big Sky’, ‘Pink Double Delight’, and ‘White Swan’), ‘Moerheim Beauty’ Helen’s flower, ‘Alma Poetschke’ New England aster, and ‘Red Grape’ spiderwort.

The five pairs in which there was no difference in bee attraction included ‘Golden Jubilee’ anise hyssop, ‘Hello Yellow’ milkweed, ‘Fried Green Tomatoes’ cardinal flower, ‘Husker Red’ penstemon, and ‘Claire Grace’ bee balm.  ‘Lavender Towers’ Culver’s root attracted more bees than the species.

The message so far from Annie’s research (pollinatorgardens.org) is that bee preference for cultivar or species will vary with the plant but, in general, native species are a better bet.  If you can’t find native species, cultivars of flowers are usually better than none.  Future research may show that many of our introduced non-native flowers also are useful for pollinators.

If all these lists and research results seem a bit overwhelming, you might start with Annie’s ten top plants.  These are herbaceous perennials that are native to the Northeast, attract a diversity of pollinator species, and perform well and look good in home landscapes.  They are the blue giant hyssop, purple coneflower, trumpet honeysuckle, sundial lupine, Helen’s flower, Culver’s root, foxglove beardtongue, Joe-pye, New England aster, and wild bergamot.

(author’s note:  Any videos or ads appearing here, added by WordPress, are not in any way related to nor have been approved by the author.)

 

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