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POLLINATION

Ernie Muhly

"... flowers are not there for us; their beauty is not for our
pleasure. What we see has a much more serious biological
function. The kaleidoscope of flower shapes, the rainbow of
brilliant colors, the bouquet of scents - all these evolved
because it was advantageous to give some guidelines to insects
searching for nectar and pollen."
(Barth, 1991)

Nectar existed before the evolution of flowering plants, and
the secretion of nectar in the broadest sense is by no means
always associated with flowers and the process of pollination.
Nectar is a food source for many animals and consists of sugars
(sucrose, glucose, fructose), which can range in concentrations
from about 8% (crown imperial (Fritillaria imperialis), to 76%
(marjoram (Oreganum vulgar )). Nectar also contains amino acids,
proteins, organic acids, phosphates, vitamins, and enzymes.
Pollen, which is a science in itself, is also a food source which
contains 16 - 30% protein, 1 - 10% fat, 1 - 7% starch, many
vitamins, but little sugar.

While nectar and pollen provide benefits to the animal world
associated with flowering plants, the significance of pollen to
plants is that it provides for the transfer of genetic
information upon which species' survival and adaptive evolution
depends. The epoch of the angiosperms (Greek: angeion (container)
+ sperma (seed)), which has been going on now for about 135
million years, shows quite clearly that balances of mutual
advantage and mutual dependence do occur and that it is most
apparent in cases of coevolution. "The typical adaptations of
angiosperms, are adaptations of the reproductive organs to the
pollination by insects. And, (the)...highest degree of
specialization for flower visiting is found in the insects that
have evolved entirely or mainly in the epoch of the angiosperms."
(Barth, 1991)

The angiosperms, or flowering plants, contain approximately
250,000 known living species. All parts of a flower are
modifications of the leaf, and they are often linked to one
another by transitional forms. "Plant species... are either
self-fertile and set fruit or seed with their own pollen
(self-pollination), or are self-infertile and need to receive
pollen from other plants of the same species (cross-pollination).
Some self-fertile species are automatically pollinated with
pollen from their own flowers, but often the flowers are so
constructed that either wind or insects are needed to transfer
pollen from their anthers to their stigmas. Wind is the principal
pollinating agent of grasses and a few other species, whereas
most (berries, fruit, herb, legume, nut, vegetable, native and
"naturalized" plants, etc.) that have conspicuous, colored and
scented flowers, are adapted for insect pollination"(Free, 1970).

The purpose of the flower is for reproduction of the
species. Some flowers are called hermaphrodite or 'perfect type',
since they contain both stamens and pistil, while the flowers of
other species have only stamens or pistils. There also exist the
dioecious species in which some plants are male, while other
plants are female. Pollination is usually most successful when
the pollen comes from the flowers of another individual of the
same species, and not from the flower that contains the same
stigma or even from another flower on the same plant.

The advantages of cross-pollination are genetic in nature.
The stigma both receives the pollen and stimulates the male
gametes the pollen contains. It also sorts out and rejects
undesirable pollen and promotes cross-pollination, to the genetic
advantage of the plants. Cross-pollination introduces variability
among individuals which increases the range of variation in the
population. Thus, cross-pollination increases the probability
that unfavorable traits will be recessive.

Flowers exhibit a kaleidoscope of forms, colors and scents.
This imaginative diversity in the shape, color and scent of
flowers is the method by which the individual species keep
themselves distinct from one another. Each combination is unique
and causes the food-seeking insects (or other pollinators such as
some birds and bats) to remain true to that particular species as
long as possible, carrying the right pollen to the right stigma
in an energy-conserving and reliable way. Herein lies the great
difference from the random nature of wind pollination.

Plant species that share a habitat also compete for
pollinators. Another co-evolutionary adaptive trait of different
plant species that share a given habitat has been the development
of characteristic sequences of blooming times - with differences
not only in the time of day at which the flowers open and offer
food, but also in the time of the year when the plant is in
bloom. As a guide to the pollinators, many flowers bear visual
guide marks that show the way to the food after the pollinator
has landed. Occasionally the nectar and pollen guides for this
short-range orientation are very conspicuous to our eyes. In
other cases, we cannot see them, although bees can, but we can
make the ultraviolet patterns of the flower visible by using
special techniques.

The primary means of pollination are by moving air (wind),
flowing water (rain) and motile animals. In temperate latitudes,
insects are by far the most important vehicle for pollination.
While the plant's purpose in this coevolved adaptation is
pollination, the insects are all looking for food, and not
working to pollinate the flowers on purely altruistic grounds.
Insects have existed for approximately 350 million years, and
there are approximately 800,000 known species. The main groups
that visit flowers include:

Beetles which have existed for about 280 million years and
contain approximately 345,000 species (fossil and living);

Hymenoptera (ants, bees and wasps) which have existed for
about 200 million years, and contain approximately 105,000
species;

Lepidoptera (butterflies and moths), which have existed for
about 65 to 70 million years, and contain approximately 165,000
species; and,

Diptera (flies and mosquitoes) which contain approximately
90,000 species.

The most important pollinating insects are the solitary
bees, bumblebees and honeybees which are approximately 100 to 120
million years old. Zoologists have identified about 20,000
species of bees in the present day world, and they are all
members of the superfamily Apoidea which have departed from the
original wasp habit of feeding on other insects and spiders, and
have changed over to nectar and pollen. Most of these species
are solitary, which means that there is no queen bee as such.
With solitary bees, the female of the species does all the nest
building, gathering of nectar and pollen, and egg laying. The
nests of solitary bees may be clustered together in an area.

Unlike bees which forage throughout the pollen and nectar
seasons to obtain sufficient food for their young, most other
insects forage to satisfy their own immediate needs only, and
feed on a variety of food other than flowers. Many of the most
important supplementary pollinators are various Diptera (flies),
including those belonging to the genera: Bibio, Bombylius,
Calliphora, Dilophus, Eristalis, Lucilia, Platycheirus, Rhingia,
Sarcophaga, and Syrphus. The adults of Bee flies (Bombyliidae),
and Hover flies (Syrphidae), live entirely on nectar and pollen.
Butterflies and moths feed mostly on nectar, and are not
significant pollinators except by accident. The beetles feed
mostly on aphids, grubs and larvae, although some, such as the
checkered beetle, the longhorn beetle and the solder beetle are
credited with being minor pollinators.

Bumblebees, honeybees and solitary bees account for about
fifty percent of the pollination performed by insects in the
temperate latitudes, and are the most studied, both as species
and for their role in pollination. Some solitary bees (often
referred to as pollen bees), are only active during a short
season, and are known for their specialization. These include
the alfalfa leafcutter bee (Megachile rotundata); the alkali bees
(Nomia melanderi); the different species of Osmia bees including:
the orchard mason bee (Osmia lignaria propinqua Cresson), the
hornfaced bee from Japan (Osmia cornifrons), and the blueberry
bee (Osmia ribifloris); the Oxaeid bee (Ptilogossa arizonensis);
the Polyester bees (Colletes species); the shaggy fuzzyfoot bee
from Japan (Anthophora pilipes villosula); and, the Giant
carpenter bee (family Xylocopidae).

There are about 3500 species of pollen bees in North
America. Unlike the seven species of honeybees (Apis), and their
close relatives the tropical stingless bees (Melipona), pollen
bees do not make excess honey and wax that people can harvest.
Some kinds of pollen bees even live like cuckoos, laying their
eggs in the nests of other species of pollen bees. Social pollen
bees, such as bumblebees (Bombus) and some sweat bees (family
Halictidae), have small colonies with a queen and a few workers,
and are not limited to one brood generation or brief foraging
period.

The bumblebee is regarded as one of the most efficient
pollinators, and it is especially valuable in pollinating those
flowers in which its large size facilitates pollen transfer while
it is visiting the nectaries. It is also good at pollinating
flowers with deep narrow corolla tubes from which only insects
with long tongues can obtain nectar. Bumblebees (Bombus spp.)
are social insects whose colonies are at a stage of organization
which is in many ways more primitive than that of honeybees, but
more advanced than that of solitary bees.

The size of a bumblebee colony at the peak of its
development varies with the different species and there may be
considerable variation within species. A large colony whose comb
is about 15 to 23cm in diameter may have 150 to 200 bees at the
height of the season, while a small colony may be only 8cm in
diameter and have only 30 to 40 bees. The colonies are annual,
with males and queens being produced at the climax of colony
development. Only fertilized queens produced within the season
survive the winter in hibernation. Bumblebees have a unique
temperature-control mechanism which allows them to live a very
wide range of climates. Some varieties have been found as far
north as 880km from the north pole.

Coevolution is co-adaptation, that is, it is a process that
is mutually beneficial to all the partners in the process. All
nectar flowers are decorated with a corolla, and many emit a
scent that is always pleasant to the insect for which the nectar
is intended. From the plant's point of view, the reason to
attract pollinators is for pollination, and from the insect's
point of view, the scent of flowers basically falls into the
category of food acquisition - both needs are satisfied quite
conveniently. There also exist pollen flowers, such as the corn
poppy which has 2.6 million pollen grains per flower - more than
enough for both pollination and to provide as food.

If the pollinator moved unselectively back and forth among
flowers of different species it would be of little value to the
plants. It is an important prerequisite for cross-pollination
that the insects carry pollen from one flower to the stigma of
another flower of the same species. Bees in general, and the
honeybee in particular, clearly excel in flower consistency. In
addition, the ability of a successful honeybee forager that has
found a good source of forage to communicate its location to
other members of its colony, undoubtedly contributes towards the
efficiency of honeybees in exploiting the surrounding flora.

Honeybees are unique in the complexity of their language in
the insect world. The value of the honeybee as a pollinator is
several times greater than it is as a producer of honey and wax.
Honeybees not only communicate the location of a strong nectar or
pollen source to their fellow colony mates, they also bring back
to the hive the odor and taste of what they have found, so that
it can be more easily recognized by recruited foragers.

Honeybees use both sight and smell to locate a nectar or
pollen source when foraging. While humans see colors in the
range of violet to red, bees see colors in the range of
ultraviolet to orange. Bees see the variegated world of flowers
in color, but not in the colors we see. The major color groups
for bees are in the blue range (blue, indigo, violet and purple),
and in the yellow range (yellow, red-yellow, green-yellow and
yellow green). The bees suffer from "hue-confusion," a general
inability to distinguish red from black, and are generally most
sensitive to hue-discrimination in the blue-green (and violet) to
green spectral region.

Hue confusion is not a significant problem for bees though,
because, while bees' long-range action is mostly visual, their
short-range orientation is chemical (odor), and once they get
close to the forage, the flowers provide UV-guide marks for
visual short-range orientation. Ultraviolet, which for the bee
is primarily the color of the sky, is important for navigation by
sky light, and so the way to the nectar is commonly indicated by
UV-free guide marks on the flowers. Some flowers also have
furrows and bumps on their petals to guide insects by use of the
insects tactile sense.

Scent marks are even more common than visual marks on
plants. It is not only the nectar marks visual to us that are
specially scented; the UV-patterns also have an odor distinct
from that of their surroundings. And even flowers with no visual
nectar guides usually have the approach to the food source marked
by odor. The bee, having coevolved with the angiosperms, has
about forty thousand sensors (pores) on its antenna. Locating
the source of a scent is something bees are very good at.

Bees take both nectar and pollen back to their colony or
nests as food to raise brood with, and in the case of the
honeybees, as winter stores. Evolution has provided bees with
both the means to chew and digest pollen, as-well-as the ability
to sip nectar. Honeybees are not the most adapted nectar
sippers, though. The cuticle (the mouth parts), are constructed
of an admirably adaptable and variable material that has made a
great contribution to the remarkable success of insects. Their
manifold modifications range from hard toothed pincers to the
elegant proboscis with which the butterflies draw nectar from the
deepest flowers. Such modifications have enabled insects to
exploit almost all conceivable food sources.

"The length of a sucking proboscis plays a large role in view
of the diversity of flower structures and the often hidden
position of the nectar. It is a critical determinant of the
kinds of flowers an insect can profitably visit - apart from
flowers that offer their nectar openly." (Barth, 1991) Charles
Darwin was the first naturalist to postulate that insects could
be found that were capable of exploiting any nectar source,
thereby showing that proboscis length was in fact a product of
coevolution. An indication of some of the rank ordering of
sucking proboscises given by Barth, who referenced the work of
W.O. James and A.R. Chapman The Biology of Flowers, Clarendon
Press, Oxford, 1935) are as follows:

Hymenoptera
Honeybees (Apis mellifera) 6.5mm
Bumblebees (Bombus terrestris) 8-9mm;
(Bombus hortorum) 14-16mm
Other bees: Anthophora pilpes19-21mm;
Orchid bees (Euglossinae) 25-30mm

Lepidoptera
Cabbage White (Pieris brassicae) 16mm
Hummingbird hawkmoth (Macroglossum stellatarum) 25-28mm
other hawkmoths (Lanhopan morgani (Madagascar)) 30cm

Diptera
Hoverfly (Syrphus) 2-4mm
Bee fly (Bombylius discolor) 10-12mm

Nature is also a playful deceiver. Orchids (Orchidaceae)
produce no nectar or food pollen for insects. Instead, orchids
produce attractant substances that either correspond exactly to
the female sexual attractant, or have the same effect. Orchid
bees (Euglossine: 200+ spp.) are primarily solitary, although a
few species are semi-social, with the characteristic behavior of
the males to gather this odor substance (terpenes).

However, it is not only by the scent that the flower
impersonates a female insect. It is the size of flower, the fact
that elongated flowers are more effective female impersonators,
the color and color-patterns including the UV components that
increase the effectiveness of the mechanically stable, convex
labellum into fooling the immature male bees into thinking that
this is in fact a female bee. Are they fooled? While the
tactile sensation on the labellum are important in eliciting
pre-copulating movements, the bee does not fertilize the flower.
The male bees pollinate the orchids though, and for their efforts
collect the odor substances which is what they were after in the
first place - and nature has coevolved a solution that satisfied
both the needs of the orchid and the bees.

Much of what has evolved over the past 130 million years is
being destroyed by mankind in the span of less than a century.
The intensive clear cutting and cultivation of the land has
destroyed many natural food sources and nesting sites of the wild
pollinating insects. Chemical agriculture has poisoned the
plants and soils, and the planting of large areas of a single
crop tends to only provide forage for a limited period of the
season, and there may be little or no forage available to
pollinating insects at other times. Plant species are now grown
for food, or other uses, in parts of the world far from where
they originated, and sometimes in the absence of their natural
pollinators. Little, if any, of the plant breeding done today is
done with any thought about pollinating insects.

Agriculture and culture need to coexist in a manner that
respects the need for all participants - man, plants and all the
other animals that make life possible. The feral bees and even
the managed bees are dying at an alarming rate due to unnecessary
pesticide use, non-sustainable land use, and the importation of
mites and disease from other areas. Since approximately
sixty-percent of the food mankind ultimately consumes requires
pollination by insects, it would seem prudent to revise our
practices to ensure that in fact there will be pollinators
available to do the work required.

Protect both wild and managed pollinators from chemical
pesticides. Biologically based, integrated pest management and
practices that are good for wildlife will also encourage
pollinators. Since most pollinators have a flight range of less
than 100 yards, it is essential to disperse fallow areas among
cultivated crop land. The pollinators need nesting habitats such
as permanently fallow areas with dry, bare sunny soil and bushy,
weedy areas, and bee trees. And like mankind, the pollinators do
best in a chemically clean environment.

Notable American Rural and Urban Nectar and Pollen Plants

Alder (Alnus spp.)
Alfalfa (Medicago sativa)
Allium spp.
Almond (Prunus amygdalus)
Alsike Clover (Trifolium hybridum)
Angelica Tree (Aralia spinosa)
Antelope Brush (Purshia tridentata)
Apple (Malus spp.)
Apricot (Prunus armeniaca)
Arbutus (Epigaea repens)
Arrowhead (Sagittaria)
Arrow-Wood (Berthelotia sericea)
Ash (Fraxinus)
Asperula Bedstraw (Asperula galioides)
Aspen (Populus)
Aster
Avocado (Persea)

Barberry (Berberis spp.)
Basil or Mountain Mint (Pycnanthemum virginianum)
Basswood (Tilia americana)
Bean (Phaseolus spp.)
Bee Balm (Melissa officinalis)
Beech (Fagus grandifolia)
Bee Sage (Hyptis emoryi)
Bellflower (Campanula spp.)
Birdsfoot Trefoil (Lotus corniculatus)
Bittersweet (Celastrus scandens)
Bitterweed (Helenium tenuifolium)
Blackberry (Rubus fruticosus)
Black Haw (Viburnum prunifolium)
Black Mangrove (Avicennia nitida)
Black Medic (Medicago lupulina)
Blazing Star (Chamaelirium Luteum, Liatris, Mentzelia
laevicaulis)
Bloodroot (Sanguinaria canadensis)
Blueberry (Vaccinium spp.)
Blue Curls (Trichostema lanceolatum)
Blue Thistle (Eeyngium articulatum)
Bluevine (Gonolobus laevis)
Boneset (Eupatorium, E. coelestenum, E. perfoliatum, Symphytum
officinale)
Borage (Borago officinalis)
Boston Ivy (Ampelopsis tricuspidata)
Box Elder (Acer negundo)
Bramble (Rubus spp.)
Broccoli (Brassica oleracea Italica)
Broom (Cytisus, Genista)
Broomweed (Gutierrezia texana)
Buckeye (Aesculus spp.)
Buckthorn (Rhamnus spp.)
Buckwheat (Fagopyrum esculentum)
Buffalo-Berry (Shepherdia argentea)
Bur CLover (Medicago hispida)
Burdock (Arctium lappa)
Burnet (Sanguisorbia minor)
Bush Honeysuckle (Diervilla Lonicera)
Buttercup (Ranunculus spp.)
Butter Weed or Groundsel (Senecio)
Button-Bush (Cephalanthus occidentalis)

Cabbage (Brassica oleracea)
California Holly (Heteromeles arbutifolia)
California Laurel (Umbellularia califorica)
Canada Thistle (Cirsium arvense)
Carpet Grass (Lippia spp.)
Carrot (Daucus carota var. Carota)
Castor Bean (Ricinus communis)
Catalpa (Catalpa speciosa)
Catnip (Nepeta Cataria)
Catsclaw (Acacia spp.)
Cat's Ear (Hypochoeris radicata)
Celery (Apium graveolens)
Century Plant (Agave americana)
Chamise (Adenostoma fasciculatum)
Cherry (Prunus cerasus, P. ilicifolia, P. serotina)
Chestnut (Castanea dentata)
Chickweed (Stellaria Media)
Chicory (Cichorium intybus)
Chinquapin (Castanea pumila)
Clematis spp.
Cleome spp.
Cleomella (Cleomella angustifolia)
Cliff Rose (Cowania mexicana, C. stansburiana)
Climbing Boneset or Duckblind (Mikania scandens)
Clover (Trifolium spp.)
Cocklebur (Xanthium canadense)
Cogswellia (Peucedanum spp.)
Columbine (Aquilegia)
Coma (Bumelia lycioides)
Coneflower (Dracopsis amplexicalilis, Rudbeckia, Ratibeda,
Echinacea)
Coral Vine (Antigonon leptopus)
Coreopsis
Coriander (Coriandrum sativum)
Corn (Zea Mays)
Cotoneaster
Cotton (Gossypium)
Cow-Itch (Cissus incisa)
Cowpea (Vigna sinensis)
Coyote Mint (Monardella villosa)
Crab Apple (Malus)
Cranberry (Vaccinium macrocarpon)
Cranberrybush (Viburnum americanum)
Creosote Bush (Covillea glutinosa)
Crimson Clover (Trifolium incarnatum)
Crocus
Crownbeard (Verbesina)
Cucumber (Cucumis sativus)
Culver's Root (Veronica virginica)
Cup Plant (Silphium perfoliatum)
Current (Ribes spp.)

Dahlia spp.
Daisy (Bellis, Chrysanthemum frutescens, C. Leucanthemum)
Dalea (Parosela)
Dandelion (Taraxacum officinale)
Dead Nettle (Lamium)
Dogbane (Apocynum spp.)
Dogwood (Cornus spp.)

Elderberry (Sambucus canadensis)
Elm (Ulmus spp.)
Eucalyptus
Everlasting (Anaphalis margaritacea)

False Indigo (Amorpha, A. fruticosa, Baptisia)
Farkle-Berry (Vaccinium arboreum)
Figwort (Scrophularia marilandica)
Filbert (Corylus americana, C. avellana)
Fireweed (Epilobium angustifolium, E. hieracifolia)
Flax (Linum usitatissimum)
Foxglove (Digitalis purpurea)

Gallberry (Ilex glabra)
Geranium
Germander (Teucrium canadense)
Giant Cactus (Cereus giganteus)
Gilia spp.
Gladiolus
Globe Thistle (Echinops sphaerocephalus)
Golden Aster (Chrysopsis)
Golden Honey Plant (Actinomeris alternifolia)
Goldenrod (Solidago spp.)
Gooseberry (Ribes spp.)
Grape (Vitis spp.)
Grapefruit (Citrus decumana)
Grasses
Ground Ivy (Nepeta glechoma)
Gumweed (Grindelia squarrosa)

Hackberry (Celtis spp.)
Hawkweed (Hieracium spp.)
Hawthorn (Crataegus spp.)
Hazelnut (Corylus americana)
Heartsease (Polygonum)
Heather (Calluna vulgaris)
Hedge Mustard (Sisymbrium altissimum)
Hedge Nettle (Stachys)
Heliotrope (Heliotropium curassavicum)
Hellebore (Helleborus viride)
Hickory (Carya spp.)
Holly (Ilex spp.)
Hollyhock (Alcea rosea)
Honey Locust (Gleditsia triacanthos)
Honeysuckle (Aquilegia canadensis, Justicia californica,
Lonicera, Rhododendron prinophyllum)
Hop Clover (Trifolium procumbens)
Hops (Humulus Lupulus)
Hop-Tree (Ptelea trifoliata)
Horehound (Marrubium vulgare)
Horsemint (Monarda)
Hound's-Tongue (Cynoglossum officinale)
Huajillo (Acacia Berlandieri)
Huckleberry (Gaylussacia, Vaccinium)
Hydrangea
Hyssop (Agastache nepetoides, A. spp. Hyssopus, H.
Officinallis)

Ice Plant (Mesembryanthemum aequilaterale)
Indian Corn or Maize (Zea mays)
Indian Currant (Symphoricarpos orbiculatus)
Indigo Bush (Amerpha fruticosa, Dalea spinosa)
Indigo-Weed (Baptisia tinctoria and B. australis)
Ironweed (Vernonia, Baldwinii)
Ironwood (Olneya Tesota)
Ivy (Hedera Helix)

Jackass Clover or Stinkweed (Wislizenia refracta)
Jerusalem artichoke (Helianthus tuberosus)
Jerusalem Thorn (Parkinsonia)
Jewelweed or Touch-Me-Not (Impatiens spp.)

Kinnikinnik (Archtostaphylos Uva-urse, Rhus virens, R.
microphylla)

Ladino Clover (Trifolium repens latum)
Larkspur (Consolida abbigua, Delphinium spp.)
Laurel (Kalmia, K. latifolia, K. hirsuta, K. angustifolia)
Lavender (Lavandula officinalis, L. stoechas)
Leatherleaf (Chamaedaphne calyculata) Cassandra
Lemon (Citrus limon)
Lespedeza (Lespedeza bicolor, L. cyrtobatra, L. thungbergii)
Lettuce (Lactuca floridana)
Lime (Citrus acida)
Liquorice (Glycyrrhiza lepidota)
Lizard's Tail (Eriophyllum staechadifolium, Saururus cernuus)
Swamp-lily
Lobelia (Lobelia leptostachys, L. syphilitica)
Locoweed (Astragalus, Oxytropis)
Locust (Gleditsia triaancanthos Robinia pseudo-acacia)
Lotibush or Texas Buckthorn (Zizyphus obtusifolia)
Ludwigia (Ludwigia natans, L. palustris or L. pilosa)
Lupine (Lupinus affinis and L. subcarnosus)
Lycium (Lycium Carolinianum and L. halimifolium)

Madrona (Arbutus menziesii)
Magnolia (Magnolia grandiflora, M. virginiana, M. acuminata)
Mahala Mats (Ceanothus prostatus)
Mallow (Malva rotundifolia)
Manzanita or Bearberry (Arctostaphylos spp.)
Maple (Acer spp.)
Marigold (Gaillardia pulchella, also Tagetes spp.)
Marjoram (Origanum vulgare)
Marsh Fleabane (Pluchea petiolata)
Mayweed (Anthemis Cotula)
Meadow Foam (Limnanthes Douglassii)
Melons (Cucumis melo)
Mesquite (Prosopis glandulosa or P. odorata)
Mexican Clover (Richardia scabra)
Mignonette (Reseda odorata)
Milk Vetch (Astragalus haydenianus, A. obcordata or A.
sisicus)
Milkweed (Asclepias spp.)
Mint (Mentha spp.)
Mistletoe (Phoradendron flavescens)
Monument Plant (Frasera speciosa)
Morning Glory (Ipomoea spp.)
Motherwort (Leonurus Cardiaca)
Mountain Lilac (Ceanothus)
Mountain Mahogany (Cercocarpus)
Mung Bean (Phaseolus aureus)
Mustard (Brassica campestris, B. ngra, B. alba)

Nama (Hydrolea ovata)
Napa Thistle (Centaurea melitensis)
New Jersey Tea or Red-Root (Ceanothus americanus)
New Zealand Flax (Phormium tenax)

Oak (Quercus spp.)
Okra or Gumbo (Abelmoschus esculentis, Viola palmata)
Oleaster, Wild Olive, Russian Olive (Elaeagnus angustifolia)
Onion (Allium spp.)
Orange (Citrus sinensis)
Oregon Grape (Berberis nervosa)
Ox-Eye Daisy (Chrysanthemum leucanthemum)

Pagoda-Tree (Plumeria rubra forma aculifolia, Sophora
japonica)
Palmetto (Sabal spp.)
Palo Verde (Cercidium torreyana)
Parsnip (Pastinaca sativa)
Partridge Pea (Cassia Chamaechrista)
Passion Flower (Passiflora spp.)
Paulownia (Paulownia tomentosa)
Peach (Prunus persica)
Pea, Garden (Pisum sativum)
Pear (Pyrus spp.)
Pennyroyal (Mentha Pulegium)
Pentstemon or Beard Toung (Pentstemon laevigatus, P. barbatus
coccineus and P. grandiflorus)
Peony (single varieties) Paeonia
Pepperbush (Clethra alnifolia)
Pepper-Tree (Schinus molle)
Perilla (Perilla frutescens)
Persimmon (Diospyros virginiana)
Phacelia (Phacelia spp.)
Physostegia or False Dragon Head (Physostegia virgininia)
Phyllodoce (Phyllodoce empetriformis, P. glanduliflora)
Pickerel-Weed or Wampee (Pondeteria cordata)
Pin Clover or Filaree (Erodium cicutarium)
Pinkmint (Stachys drummondii)
Plum (Prunus spp.)
Pond Lily (Nymphaea advena)
Poplar (Populus spp., Liriodendron Tulipifera)
Poppy (Papaver, P. somniferum, Eschscholtzia californica,
Argemone and Kallstroemia
grandifolia)
Portulaca
Prairie Clover (Petalostemon)
Prairie Crocus (Anemone patens) Pasque Flower
Prairie Parsley (Polytaenia Nuttallii)
Prickly Ash (Xanthoxylum Clava-Herculis) Toothache-Tree
Prickly Pear or Indian Fig (Opuntia spp.)
Prince's Plume (Stanleya)
Psoralea (Psoralea Onobrychis, P. lanceolata, P. argophylla,
P. esculenta)
Pumpkin (Cucurbita spp.)
Purple-Flowered Mint (Mesosphaerum spicatum, M. rugosum (swamp
basil))
Purple Loosestrife (Lythrum Salicaria, L alatum, L.
ovalifolium)

Queen Anne's Lace (Daucus Carota var. Carota)
Quince (Cydonia oblonga, C. japonica)

Rabbit Brush (Chrysothamnus nauseosus and C. lanceolatus)
Radish or Jointed Charlock (Raphanus Raphanistrum, R. sativus)
Ragweed (Ambrosia trifida)
Rape (Brassica Napus)
Raspberry (Rubus idaeus, R. occidentalis)
Rattan Vine (Berchemia scandens)
Rattlesnake-Root (Nabalus altissimus)
Red Bay (Persea Borbonia)
Red-Bud (Cercis canadensis, C. reniformis and C. occidentalis)
Red Clover (Trifolium pratense)
Red Maids (Calandrinia caulescens)
Redroot (Gyrotheca tinctoria)
Rocky Mountain Bee Plant (Cleome integrifolia, C. serrulata)
Rose (Rosa spp.)
Rosemary (Rosmarinus officinalis) Old Man
Russian Thistle (Salsola pertifera)

Safflower (Carthamnus tinctorius)
Saffron (Crocus sativus)
Sage (Salvia spp.)
Sainfoin or Esparcet (Onobrychis sativa)
Salal (Gaultheria shallon)
Salmonberry (Rubus spectabilis)
Sand Cherry (Prunus pumila)
Sassafras (Sassafras officinale)
Savory (Satureia hortensis and S. montana)
Scilla (Scilla siberica)
Screwbean (Prosopis pubescens)
Sea Grape (Coccolobis uvifera)
Sea Lavender (Limonium brasiliense, L. carolinanum)
Self-Heal (Prunella vulgaris)
Senisa (Leucorphyllum texanum)
Senna (Cassia spp.)
Serviceberry or Juneberry (Amelanchier)
Skunk Cabbage (Lysichiton americanum, Symplocarpus foetidus,
Veratrum californicum)
Snowberry (Symphoricarpos racemosus) Waxberry
Snow Brush (Ceanothus velutinus)
Snow-On-The-Mountain (Euphorbia marginata) Spurge
Soapbush (Guaiacum angustifolium)
Soap Plant or Soap Root (Chlorogalum pomeridianum)
Sorghum
Sorrel (Rumex acetosella)
Sour Clover (Melilotus indica)
Sourwood (Oxydendrum arboreum)
Sow Thistle (Sonchus)
Soybean (Glycine soja)
Spanish Needle (Bidens aristosa, B. frondosa, B. involucrata,
B. laevis, B. leucantha, B.
pilosa, B. trichosperma)
Speedwell (Veronica spp.)
Spider Plant (Cleome spinosa and C. lutea)
Spiderwort (Tradescantia virginiana)
Spikeweed (Centromadia pungens)
Spring Beauty (Claytonia Virginica)
Squash (Cucurbita maxim and C. moschata)
Star Thistle (Centaurea) Barnaby's Thistle
Stonecrop (Sedum pulchellum)
Stone Mint (Cunila origanoides) Maryland Dittany
Strawberry (Fragaria spp.)
Sumac (Rhus spp.)
Summer Farewell (Kuhnistera pinnati)
Sunflower (Helianthus spp.)
Swamp Loosestrife (Decondon verticillatus)
Sweet Clover (Melilotus alba, M. officinalis)
Sweet Fennel (Foeniculum vulgare)
Sycamore (Platanus occidentalis, P. racemosa)

Tallow Tree (Sapium sebiferum)
Tarweed (Hemizonia)
Teasel (Dipsacus fullonum) Fuller's Teasel (D. sativus)
Thimble Berry (Rubus parviflorus)
Thyme (Thymus spp.)
Ti-Ti (Cyrilla racemiflora or Cliftonia momophylla)
Trillium spp.
Tulip-Poplar or Tulip Tree (Liriodendron tulipifera)
Tupelo (Nyssa ogeche, N. biflora, N. aquatica, N. sylvantica)
Turnip (Brassica rapa)

Vanilla-Plant or Deer-Tongue (Trilisa odoratissima)
Velvet Bean (Mucuna utilis)
Vervain (Verbena spp.)
Vetch (Vicia spp.)
Vine Maple (Acer circinatum)
Virginia Creeper (Parthenocissus quinquefolia)
Virginia Waterleaf (Hydrophyllum virginicum)

Walnut (Juglans spp.)
Water Chinquapin (nelumbo lutea) Duck Acorn
Water Elm (Planera aquatica) Planer Tree
Water Horehound (Lycopus) Bugle-Weed
Watermelon (Citrullus lanatus)
Water Plantain (Alisma)
Watershield (Cabomba caroliniana)
Water-Willow (Dianthera americana)
Wax Myrtle (Myrica cerifera) Waxberry
White Clover (Trifolium repens)
Wild Alfalfa or Deer Clover (Lotus glaber)
Wild Buckwheat (Eriogonum spp.)
Wild Cabbage (Caulanthus crassicaulis)
Wild Cherry (Prunus serotina)
Wild Cucumber (Echinocystis lobata)
Wild Hyacinth (Camassia esculenta)
Wild Peach (Prunus Caroliniana)
Wild Pennyroyal (Satureia rigidi)
Willow (Salix spp.)
Winter Cress (Barbarea vulgaris) Yellow Rocket
Wolfberry (Symphoricarpos occidentalis)
Wood Mint (Blephilia ciliata)

Yellow-Top (Verbesina encelioides)
Yellow Wood (Cladrastis lutea)
Yucca spp.

Ed. note: this list contains some weedy or exotic species
that are not recommended to be planted such as the tallow tree.

Suggested Reading and References

Bart, Friedrich G. Insects and Flowers: The Biology of a
Partnership. Princeton, NJ: Princeton University Press, 1991.

Buchmann, Stephen L. and Gary Paul Nabhan. The Forgotten
Pollinators. Washington, DC: Island Press, 1996.

Free, John B. Insect Pollination of Crops. London: Academic
Press Inc., Ltd., 1970.

Hubbell, Sue Broadsides from the Other Orders: A Book of Bugs.
New York: Random House, 1993.

Huxley, Anthony J. Green Inheritance: the World Wildlife Fund
Book of Plants. London: Gaia Books Ltd., 1992.

Pellett, Frank C. American Honey Plants Hamilton, IL: Dadant
and Sons, 1976.

Wilson, Edward O. The Diversity of Life. Cambridge, MA: Belknap
Press, 1992.