“Proven Functionals”: Herbaceous Plants That Attract Pollinators

When Marjorie and I visit a local garden center in early spring, we’re usually searching for a short list of annuals and herbaceous perennials, the perennials for the island bed and borders in Marjorie’s Garden, the annuals for both garden beds and containers. The one characteristic common to each plant on the list is that it will attract pollinators and other beneficial insects.

On these visits we see the words “Proven Winners” on many plant labels, but the plants that carry those labels are rarely on our list. “Proven Winners” is a brand name that represents one company’s products, plants selected, according to the brand’s website, for ease of growing, prolific and colorful flowers, all-season flowering, and disease resistance. There is no emphasis on how these plants function in the garden, i.e. does a “Proven Winner” attract pollinators and other beneficial insects to the garden? In other words, in this gardener’s opinion, the company is devoted to marketing eye candy, not garden-worthy plants.

So, dear reader, I offer my own epithet for herbaceous plants, both annual and perennial, that attract bumble bees, native solitary bees, hoverflies, and other beneficial insects: “Proven Functionals”. They are all easy to grow, many from seed, and the annuals can be grown in containers scattered about the garden. They all have colorful flowers and continue to bloom all season if deadheaded regularly. They belong in the garden that is truly in tune with nature.

The following list is based on our experience with the plants, in some cases for many years. I present six of my “Proven Functionals” below, four annuals and two perennials, with more to come in future columns. All of these plants can be easily grown by the gardener from seed or purchased as transplants from a local garden center.

Cosmos (Cosmos bipinnatus)

Cosmos FlowersCosmos is both the common name and the genus name for an extensive variety of flowering annuals. Our favorite group for planting in garden beds are the Sensation series, a group of tall (4-5 feet) plants with large 3-4 inch daisy-like blossoms with yellow centers. We grow the Sensation Mix from seed, ending up with plants that bloom in various shades of red, pink, and white. These are among the tallest of cosmos, their lacy foliage the perfect foil for the bright white blossoms of flowering tobacco (Nicotiana alata ‘Only the Lonely’).

Flowers of the Sea Shells series have fluted petals.

Flowers of the Sea Shells series have fluted petals.

This summer we also grew Sea Shells Mix, an unusual flower form with large fluted petals in a wide range of solid colors and bicolors. It grows to 4 feet tall. In large pots we like to grow the Bright Lights series, multi-branched plants that grow 3-4 feet tall with semi-double flowers in shades of scarlet-orange, golden-orange, gold, and yellow.

Throughout July and August, bumble bees, native solitary bees, and the occasional butterfly were the primary pollinators visiting our cosmos plantings.

Bachelor’s Buttons
(Centaurea cyanus)

Batchelor's buttons at the garden gate.  The strong pink flowers in the background are perennial sweet peas.

Batchelor’s buttons at the garden gate. The strong pink flowers in the background are perennial sweet peas.

Of all the annuals in Marjorie’s Garden this season, the annual bachelor’s buttons (also called cornflower) was the most frequently visited by pollinators, including bumble bees, native solitary bees, honeybees, hoverflies, and butterflies. We grew our plants from seeds started in early May and transplanted the seedlings to pots and garden beds in mid-June. The first purple-blue, pink, and white flowers appeared in early July and the frequently deadheaded plants are still flowering on 2- to 3-foot tall stems.

Plants that are not deadheaded provide seeds that are loved by goldfinches and other birds. We plan to stop deadheading soon so that the last crop of flowers can feed our garden’s birds.

(I realize that this species is listed as either a noxious weed or as invasive in Maine and several other states. In fact, it has escaped cultivation and is now naturalized in human-disturbed areas including fields, waste grounds, along roadsides and roadsides. I have found no report of it entering relatively undisturbed habitats and outcompeting native plant species for resources and thus I do not consider it to be truly invasive.)

Calendula (Calendula officinalis)

Cosmos plants along the vegetable garden paths are self-sown each year.

Cosmos plants along the vegetable garden paths are self-sown each year.

Calendulas, or pot marigolds, are a must annual for anyone interested in attracting pollinators to the garden. Once you grow calendulas in your garden, you will always have them. Plants in pots or in the ground will scatter seeds over a wide area and the following spring their bright green strap-like seedlings will pop up everywhere. We leave them to grow along the bed edges of the vegetable garden and transplant those that are in the beds to pots, or to empty spots along the beds edges. Wherever they are grown, the daisy-like bright yellow to deep orange blossoms which brighten the garden from mid-summer into fall are a favorite of the small native solitary bees.

Calendula petals are edible, often added fresh or dried to salads, soups, and rice dishes to add both color and flavor. Flavors range from spicy to bitter, tangy to peppery, and in my experience a little goes a long way.

Calendulas are easy to grow from seed started 6-8 weeks before last frost or sown directly in the garden in early spring. Transplants should be set out after the last frost.

Wild Bergamot (Monarda fistulosa)

Wild bergamot flowers are a soft mauve-pink color.

Wild bergamot flowers are a soft mauve-pink color.

Wild bergamot is a native perennial across most of the United States, including all of New England. Similar in habit and flower to the more familiar bee balm, Monarda didyma, wild bergamot is distinguished by its pink to lavender, two-lipped, tubular flowers borne in terminal heads on square stems from 2 to 3 feet tall.

At present we have but one clump of wild bergamot looking rather lonely in an island bed surrounded by other well-established perennials. Aware of its tendency to spread, both by seed and vegetatively, we are planning to relocate it to the fence line that surrounds the vegetable garden where it can spread with abandon in the summer sun.

Like bee balm, wild bergamot can be bothered by powdery mildew, particularly when grown under crowded gardens with poor air circulation. Compared to bee balm, however, wild bergamot has the better milder resistance.

The list of pollinators and beneficial insects drawn to the flowers of wild bergamot includes bumble bees, solitary bees, hummingbird clearwing moths, Eastern tiger swallowtail butterflies, silver-spotted skippers, hoverflies, and flower beetles.

Milkweeds (Asclepias incarnata and A. curassavica)

This summer, for the first time in its 15 year history, Marjorie’s Garden is host to monarch butterflies. We briefly spotted only two adult monarchs winging over the garden in mid-June, never alighting on either of the two milkweed species we have growing, but the busy gardener does not always notice the pivotal events that change the character of both garden and gardener for the rest of the season. For on July 24 we came across the first monarch caterpillar, less than an inch long, feeding on the leaves of an annual milkweed plant, a species called tropical milkweed (Asclepias carassavica) that we had grown from seed.

A monarch caterpillar munches on flower buds of the tropical milkweed, an annual that is easily grown from seed.

A monarch caterpillar munches on flower buds of the tropical milkweed, an annual that is easily grown from seed.

As they quickly became larger, they were more visible. By July 27, we counted a total of 19 caterpillars, all on tropical milkweed plants. By August 1, we could find 25 and, on August 4, they began to pupate, constructing chrysalises throughout the garden. The day before, August 3, noticing that the largest of the group were moving sluggishly, I transferred nine larvae to hatching cages with plans of tagging the adults before releasing them for their migration south. Our best guess is that the adults will emerge from these chrysalises between August 23 and 26.

Swamp milkweed is the best form of perennial milkweed to grow in the garden.

Swamp milkweed is the best form of perennial milkweed to grow in the garden.

We have also been growing a perennial species of milkweed, the swamp milkweed (A. incarnata), since the year before, but it is a late starter and was barely out of the ground when the monarchs arrived. Unlike the common milkweed (A. syriaca) which forms extensive colonies from underground stems, swamp milkweed is a tall clump-forming plant that stays put and thus is far more manageable in the garden. Its August display of mauve-pink flowers is a magnet for pollinators of all kinds.

A monarch chrysalis attached to a sweet pea vine.

A monarch chrysalis attached to a sweet pea vine.

Plant it and they will come! Next year we hope to have monarch caterpillars feeding on both the annual and perennial milkweed species. From now on there will always be milkweeds growing in Marjorie’s Garden.

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About Reeser Manley

I was born in Laramie Wyoming but moved to the southeast at an early age. I was educated through my B.S. in Biology in the Columbus, Georgia area, then crossed the Chattahoochee River to earn my M.S. in Botany at Auburn University. For the next ten years, I worked as Horticultural Manager for the George W. Park Seed Co. in Greenwood, S.C. At 40 years of age, I decided to return to graduate school and in 1994, I earned a Ph.D. in Horticultural Science from Washington State University, Pullman, Washington. Fast forward through 10 years at university (7 at UMaine, Orono) and you find me teaching high school science in Eastport, Maine, the edge of the world, and writing a weekly garden column for the Bangor Daily News. My new book, The New England Gardener's Year, a Month-by-Month Guide for Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, and Upstate New York”, will be published later this year by Cadent Publishing. You can learn more about the book by visiting its Facebook page: http://www.facebook.com/pages/The-New-England-Gardeners-Year/187285218055676.)