100 Plants to Feed the Bees

This book is dedicated to everyone who tears up their front yard to plant big chaotic wildflower gardens, to farmers who think hedgerows and wildflower field borders are just as important as crops, to urban planners and landscapers who turn gray and lifeless concrete landscapes into corridors of biodiversity, and to members of the Xerces Society.

Contents

What's Old Is New

Plants and Pollinators: An Overview

Pollinators and Pesticides

1. Native Wildflowers

1. Anise Hyssop, Giant Hyssop

2. Aster

3. Beebalm

4. Black-Eyed Susan

5. Blanketflower

6. Blazing Star

7. Blue Curls

8. Blue Vervain

9. California Poppy

10. Clarkia

11. Coreopsis

12. Culver's Root

13. Cup Plant, Compass Plant, Rosinweed

14. Figwort

15. Fireweed

16. Globe Gilia

17. Goldenrod

18. Gumweed

19. Ironweed

20. Joe-Pye Weed, Boneset

21. Lobelia

22. Lupine

23. Meadowfoam

24. Milkweed

25. Mountainmint

26. Native Thistle

27. Penstemon

28. Phacelia

29. Prairie Clover

30. Purple Coneflower

31. Rattlesnake Master, Eryngo

32. Rocky Mountain Bee Plant

33. Salvia

34. Selfheal

35. Sneezeweed

36. Spiderwort

37. Sunflower

38. Waterleaf

39. Wild Buckwheat

40. Wild Geranium

41. Wild Indigo

42. Wingstem

43. Wood Mint

2. Native Trees and Shrubs

44. Acacia

45. Basswood

46. Blackberry, Raspberry

47. Black Locust

48. Blueberry

49. Buckwheat Tree

50. Buttonbush

51. Chamise

52. Coyotebrush

53. False Indigo, Leadplant

54. Golden Currant

55. Inkberry

56. Madrone

57. Magnolia

58. Manzanita

59. Mesquite

60. Ocean Spray

61. Oregon Grape

62. Rabbitbrush

63. Redbud

64. Rhododendron

65. Rose

66. Saw Palmetto

67. Serviceberry

68. Sourwood

69. Steeplebush, Meadowsweet

70. Toyon

71. Tulip Tree

72. Tupelo

73. Wild Lilac

74. Willow

75. Yerba Santa

3. Introduced Trees and Shrubs

76. Orange

77. Plum, Cherry, Almond, Peach

4. Introduced Herbs and Ornamentals

78. Basil

79. Borage

80. Catnip

81. Coriander

82. Cosmos

83. Hyssop

84. Lavender

85. Mint

86. Oregano

87. Rosemary

88. Russian Sage

89. Thyme

5. Native and Nonnative Bee Pasture Plants

90. Alfalfa

91. Buckwheat

92. Clover

93. Cowpea

94. Mustard

95. Partridge Pea

96. Radish

97. Sainfoin

98. Scarlet Runner Bean

99. Sweetclover

100. Vetch

Average Number of Flower and Herb Seeds per Pound

Photo Credits

Other Storey Books

Copyright

Share Your Experience!

What's Old Is New

Dr. Edith Patch was the original insect ­conservationist, one of the first critics of indiscriminate pesticide use, an author of fantastically interesting children's books, and an early pioneer for women in science. But it was in her role as the first female president of the Entomological Society of America, at the organization's annual meeting in 1936, that Edith foreshadowed this exact book and everything we do here at the Xerces Society in a lecture titled "Without Benefit of Insects."

In that talk Edith discussed the wholesale destruction of insect life that had resulted from the new insecticide products that were being brought to market, and commented on how in attempting to control pests, we were destroying bees and beneficial insects. She challenged the assembled scientists to imagine a very different world in the year 2000, when she predicted that the president of the United States would issue a proclamation declaring that land areas at regular intervals throughout the country would be maintained as "Insect Gardens," directed by government entomologists. These would be planted with milkweed and other plants that could sustain populations of butterflies and bees. She then predicted that at some time in the future, "Entomologists will be as much or more concerned with the conservation and preservation of beneficial insect life as they are now with the destruction of injurious insects."

Although the exact year she predicted turned out to be slightly early, Edith was ultimately right. In the summer of 2015, after extensive behind-the-scenes talks between the White House, Xerces, and other conservation groups, President Barack Obama did indeed release a first-of-its-kind memorandum. It called upon all federal agencies to do two things:

1. 1. To develop comprehensive conservation plans that would protect and restore habitat for bees and butterflies at federal facilities and on federal lands
2. 2. To offer financial incentives for the restoration of pollinator habitat on private lands, especially farmlands

The president also issued a challenge to the conservation community to help foster a million new pollinator gardens in residential yards and business campuses across the country — an effort Xerces is supporting through our Bring Back the Pollinators Garden Campaign (xerces.org/bringbackthepollinators).

While the accuracy of Edith's prediction is both haunting and heartening, amazingly she was not alone in pioneering the call to create habitat for pollinators. Twenty years earlier, in fact, Iowa polymath Frank Chapman Pellett established near his childhood home what may have been the first large-scale bee garden in the United States. Although formally trained as a lawyer, Frank eschewed the basic trappings of prosperity, choosing instead to live in Gandhi-like midwestern simplicity in a small, plain farmhouse. There he researched tomato gardening, devoted countless hours to bird watching, and meticulously documented and cultivated the preferred wild pollen and nectar sources of his honey bees.

His ceaseless hours of observation resulted in the 1920 book American Honey Plants, possibly still the best publication of its kind in existence. In another book, Our Backyard Neighbors, Frank wrote of himself and his pollinator garden in the third person, saying, "There were many wild flowers, such as asters and goldenrod, crownbeard and rudbeckia, which the neighbors regarded as weeds, but which the Naturalist guarded with jealous care."

Along with Edith Patch and Frank Pellett, the late Canadian scientist Dr. Eva Crane played one of the largest roles in further inspiring early thinking about pollinator gardens. Although she was formally educated as a quantum mathematician and nuclear physicist, the gift of a beehive in 1942 (as a supplement to wartime sugar rationing) led Eva to devote the next five decades of her life to publishing nearly 200 books and articles on honey plants and indigenous beekeeping.

Her writing was based on her field research in more than 60 countries, where she often lived under primitive conditions, even in her later years. Her rigorous and exacting books, such as the Directory of Important World Honey Sources, are the most comprehensive attempts of their kind to document the nutritional value of pollen and nectar from thousands of species of plants, as well as those plants' potential honey yields.

In their own ways each of these deeply inquisitive champions of pollinator habitat inspired small communities of beekeepers and conservationists to see the landscape through a different lens. Plants previously scorned as weeds and unproductive "waste" areas on farms began to have value to at least a small segment of people, even as urbanization and agriculture intensified with enthusiasm.

By 1950 even the USDA Soil Conservation Service, the agency most responsible for saving American agriculture from itself during the Dust Bowl, recognized the value of pollinators. It distributed a simple educational bulletin to Midwest farmers, featuring an illustration of bumble bees flying between a hedgerow and a clover crop with the earnest title Wild Bees Are Good Pollinators. The bulletin lists important habitat areas on the farm to protect for pollinators, including stream banks, woodlots, shelterbelts, and field borders. For good effect the bulletin even features an illustration of a bag of clover seed with a dollar sign across its front.

Surprisingly, the dawn of the environmental movement brought little attention to pollinators during the 1960s, '70s, and '80s, although countless other important conservation issues finally received some long-overdue attention. Only when large-scale honey bee losses began to make headlines in 2006 did the conservation community again focus much on the role of pollinators. By that time several bumble bee species in the United States were dwindling toward extinction, and once-common monarch butterfly populations were in free fall. Now books and articles about pollinator conservation are everywhere. For those of us at Xerces who have been working on and writing about pollinators for decades, this long-overdue attention is gratifying and energizing.

The spiritual tradition of this particular book descends from Patch, Pellett, and Crane, but also from John Muir, Aldo Leopold, Rachel Carson, and many others. These are the writers who inspired us here at Xerces in our youth and early in our careers, and who ultimately helped bring us all together as the big extended family that we are today. Our goal, like that of the conservation writers who preceded us, is not just to preach the gospel, but also to invite you into the tribe. We hope that you will join us.

The initiation is simple: just plant flowers.

Plants and Pollinators: An Overview

When we observe animals pollinating nearly 90 percent of the plant species found on earth, we are witnessing a process more than 250 million years in the making. Sexual reproduction among plants, from a botanical standpoint, is nothing more than the transfer of pollen grains from a flower's male anthers to a flower's female stigmas, enabling fertilization. Once transferred, pollen grains germinate, grow pollen tubes into the plant's ovaries, and deliver gametes to produce seed and endosperm.

In very primitive plants, this process was carried out by wind or water. Between 245 million and 200 million years ago, however, the first flowering plants arose, with the earliest fossil records containing relatives of today's magnolias and water lilies. During this prehistoric time frame, flowering plants evolved two major reproductive adaptations: exposed male stamens that bear small, nutrient-rich pollen grains; and enclosed female carpels that protect ovules. These adaptations accelerated plant reproduction (and pollinator diversity), leading to diverse and dominant communities of flowering plants that almost 100 million years ago had spread across the globe.

Plants Meet Pollinators

Beetles, flies, and wasps are thought to be the first pollinators, accidentally spreading pollen while feeding on flowers. This set the stage for more complex plant-pollinator relationships to evolve, including prehistoric flowering plants that first attracted passive pollinators by providing sugary nectar, protein-packed ­pollen, fragrant resins, and vitamin-rich fats.

Flowers then responded to particular pollinators, coevolving with them to provide diverse bloom times, colors, scents, shapes, sizes, and rewards, and improving their reproductive efficiency. For example, flattened, large, scented, off-white flowers with accessible pollen, such as magnolia, attracted beetles, while tubular, large, scented, white flowers that bloom at night attracted moths.

Meanwhile, flowers also developed a variety of strategies to avoid self-fertilization and encourage genetic diversity:

• self-incompatibility
• physical distance between (male) anthers and (female) stigmas
• male and female flower structures that are fertile at different times
• separate male and female plants

Enter the Bees

The widespread distribution of diverse flowering plants 100 million years ago coincided with the appearance of intentional pollinators: bees. Bees are believed to have coevolved with flowers from predatory wasps. In general, both bees and wasps consume sugars as adults and proteins as larvae. Herbivorous bee larvae eat pollen as their protein source, however, while wasp larvae are typically carnivorous.

Pollen is essential for the reproduction of both bees and flowers, so the two groups have coevolved for mutual success. Adult bees evolved behavioral and physiological adaptations to gather and transport pollen more efficiently, such as:

Buzz-pollination. Flight muscles can create sound vibrations that dislodge pollen from flowers.

Floral constancy. An individual pollinator may specialize in foraging one flower type.

Pollen-collecting hairs. The "pollen basket" and other specialized hairs on a bee's body carry pollen back to the colony.

Although most bees are pollen generalists, capable of foraging on many plant species, many are specialists that forage on only a small group of specific flowers.

What Makes a Good Pollinator Plant?

A flower's color, odor, shape, size, timing, and reward (nectar or pollen) can increase or decrease the number of visits by specific pollinators. Some examples of how plants "reach out" to bees and others:

Ultraviolet invitations. Bees can see ultraviolet light but not red light; thus, flowers in the ultraviolet range attract more bee visits, while red-hued flowers reduce them.

Color phases. Many flowers signal pollinators by changing color at different stages of development, attracting pollinators when they need them most, thus increasing the efficiency of the pollinators they depend upon.

Nectar Guides. Contrasting patterns of flower shades, tints, and tones further direct pollinators toward floral rewards such as nectar or pollen, much like the nighttime runway lights of an airport.

Fragrance. Minty or sweet, musky or ethereal, pungent or putrid, floral odors result from variations in chemical compounds. Fragrance can attract particular pollinators over long distances, varying in concentration and intensity according to species, flower age, and site conditions.

Flower shape, size, and timing work together with color and odor to regulate pollinator visits. Abundant and diverse shapes and sizes, symmetrical or asymmetrical forms, arrangements on stems or branches in simple or complex groups, maturing at different rates: these variations can make it easier or harder for visitors to reach nectar and pollen.

For example, shallow, clustered flowers with landing platforms (such as sunflowers) have easily accessible floral rewards and attract many short-tongued pollinators such as sweat bees, beetles, and flies. In contrast, deep or tubular flowers without landing platforms often have hidden floral rewards accessible only by long-tongued or strong pollinators. A classic example of this latter flower type is bottle or closed gentian (Gentiana spp.), whose flowers remain closed and depend for pollination on bumble bees, which pry the petals apart and climb right inside.

Finally, many plants bloom according to a distinct seasonal rhythm — their phenology — which may be closely timed with the life cycle of specific pollinators. Others, meanwhile, bloom continuously or irregularly during the growing season, attracting many different types of pollinators. These rhythms can invite or exclude different pollinators depending upon the season or even the hour.

Risks and Rewards of Flower Foraging

Of course, pollinators most often visit flowers for nutrient-rich food rewards: pollen and nectar. The availability and quality of these rewards vary depending on time of day, environmental factors, and an individual plant's life cycle. And from the perspective of a bee, butterfly, or other pollinator, several factors can make a particular flower useful, or not.

Nutrition

Floral rewards include pollen, nectar, oils, and/or resins, depending on the plant species.

Pollen, the most protein-rich of these rewards, is essential to bee reproduction. Once gathered, adult bees typically mix pollen with nectar and glandular secretions to form a nutritious "bee bread," which forms the diet of larval bees. Pollen grains vary from 10 to 100 micrometers in size, have distinctive shapes, and commonly contain protein levels ranging from 2 to 60 percent (including 10 essential amino acids, as well as varying concentrations of carbohydrates, lipids, sterols, and other micronutrients). While some bees, such as the common European honey bee, are generalist pollinators whose diets are not restricted to particular pollen types, others are specialists of pollen from particular flowers, including various mining bees, cellophane bees, and resin bees.

Nectar is composed chiefly of carbohydrates and water, with low levels of amino acids, lipids, proteins, and various vitamins and minerals. Carbohydrates, primarily the sugars sucrose, fructose, and glucose, can range in concentrations from 10 to 70 percent based on species and weather. It is this sugar-rich food source that fuels adult bees, butterflies, and a myriad of other flower visitors, such as bats and hummingbirds. Nectar secretion, even within the same species of plant, can vary depending on humidity, precipitation, time of day, temperature, wind, latitude, soil, and various other factors. In turn, the pollinators visiting those blossoms may encounter short-term booms and busts of nectar availability.

Oils and resins are secreted by some flowers to attract bees. Specialized floral glands produce calorie-rich, medicinal oils that are regularly collected by a few bees (for example, Macropis spp. and Melitta spp.) and mixed with pollen and nectar for feeding and medicating larvae. Most likely, such flower resins first evolved to protect the plants from herbivores or disease. Eventually bees came to use them as a food source, and as a resin for constructing anti-microbial and waterproof nests.

Nonfloral Rewards

Nonfloral (or "extrafloral") rewards include nectar, honeydew, fruits, and saps.

Extrafloral nectar is produced by many plants as sugary droplets from glands on leaves, stems, and other nonflowering plant parts. These nectar droplets attract beneficial predatory insects, such as ants, beetles, flies, mites, spiders, and wasps — all of which may attack plant pests. Among some plants, these extrafloral nectaries may supply even more nectar than the flowers do themselves. While less showy and aromatic than flowers, extrafloral nectaries are usually open and exposed for easy access by many types of beneficial insects (although not infrequently they are guarded by territorial ants!).

Honeydew is the sugary excrement of sap-feeding aphids, scale insects, whiteflies, and some butterfly caterpillars (mostly the blues, in the family Lycaenidae). Like extrafloral nectar, it is eagerly collected by many beneficial insects, including ants, bees, and wasps. In some locations, in fact, aphid honeydew is found in large enough quantities to produce small surplus honey crops. Honeydew is readily accessible but occasionally it, or the insects producing it, are guarded by ants. Think of ants tending aphids as though they were livestock, and you have a fairly accurate picture of this unique insect relationship.

Propolis, also known as bee glue, is a resinous sap mixture collected from plants by bees and harvested by humans. Particular plants, including conifers and poplars, exude these resins from buds or from injuries as a natural antimicrobial defense.

Honey bees collect propolis to construct and defend hives, weatherproof small cracks and holes, smooth surfaces, dampen vibrations, and protect themselves from bacteria, fungi, mites, and other intruders. Humans harvest and use honey bee propolis in ­cosmetics, soaps, medicines, and wood polishes or varnishes.

Species of solitary mason bees also collect propolis to construct, partition, and seal nests.

Other Rewards

Beyond pollen and nectar, plants sustain pollinators in several other ways, and the most familiar of these is as caterpillar food for butterflies. With only a few exceptions, the vast majority of butterfly and moth caterpillars are herbivores that feed exclusively on plant foliage. Depending on the species, those caterpillars may be generalists, which can feed on many types of plants, or specialists with a very narrow range of plants on which they can successfully feed.

The specialists often acquire defensive chemical compounds from the plants they feed upon (such as alkaloids, cardenolides, or glycosides) that make those insects unpalatable or toxic to predators. For example, milkweed butterfly caterpillars such as the monarch and queen feed exclusively on milkweed (Asclepias spp.) foliage, which contains toxic cardenolides that repel most vertebrate predators.

Other than food resources, plants also offer nesting, egg-laying, and overwintering resources for pollinators, such as hollow or pithy canes; stalks, stems, or twigs; leaves, petals, or plant fibers; and exfoliating or peeling bark. Plants with hollow or pithy branches, such as brambles (Rubus spp.), elderberry (Sambucus spp.), and sumac (Rhus spp.), are used extensively as nesting spaces for a wide range of wild solitary bees and wasps.

Nearly 30 percent of North American native bee species nest in hollow stems or abandoned beetle borer holes — including leafcutter bees (Megachile spp.), mason bees (Hoplitis spp.; Osmia spp.), small carpenter bees (Ceratina spp.), and masked bees (Hylaeus spp.).

Leafcutter bees cut round sections of leaves or petals to wrap around their developing larvae and pollen stores, similar to a carefully wrapped origami package.

Wool Carder bees (Anthidium