4 Parade of Pollinators
Animals that pollinate flowers include creatures that are very familiar, such as bumble bees and honey bees, as well as less obvious animals. There are pollinating beetles, bats, butterflies, moths, lizards, rodents, lemurs, honey possums, and even monkeys. Not every species within a group of animals is a pollinator. Approximately 9 percent of all birds and mammals on Earth are pollinators. One of the most unusual mammal pollinators is the lemur, which is the largest pollinator in the world.
Meet the Pollinators
The vast majority of pollinators are insects, which are often grouped into four major categories: bees and wasps, flies, butterflies and moths, and beetles. It is often said that insects, particularly bees, are the most important pollinators on the planet. Bees do pollinate more crop plants than other pollinators, but the importance of a pollinator really depends on the plant in question. If a pollinating bat species becomes extinct—and note that bats are declining globally—the plants that depend on that species for pollination will also vanish.
Multiple pollinators on rattlesnake master (Eryngium yuccifolium)
Think of your landscape as an ecosystem that can support many different pollinating species. Let’s take a look at some of the pollinators you could potentially attract to your garden.
Native Bees
Across the globe there are approximately 20,000 species of bees; 3,600 of these are native to the United States and Canada. Native bees are the bees that occur naturally in an ecosystem. That may sound obvious, but many Americans still think that honey bees, introduced to North America by colonists in 1622, are native to the United States. There are other nonnative bees in North America, with approximately forty species that have been introduced accidentally or intentionally.
Native Bee Lifestyles
Native bees are very different from social honey bees. Ninety percent of native bees are solitary and nest alone; the other 10 percent are social, but to a much lesser degree than honey bees. Bumble bees are our only truly social native bees in North America, nesting in groups of approximately fifty to four hundred individual bees, depending on the bumble bee species. Of all the species of native bees in North America, approximately forty-seven species are bumble bees.
Whereas a honey bee colony is concentrated in a single hive, native bees with their solitary or quasi-social lifestyles require a much broader expanse of habitat in your landscape.
Wherever you garden, there are plenty of native bees to support! It is estimated that within a mile of any landscape, urban or rural, there may be one hundred or more species of native bees present.
Managed Bees
Honey bees are not the only bees managed by humans for pollination services. Although less commonly used, several species of native bees that excel at pollination of certain plants can be somewhat domesticated. Mason bees, leafcutter bees, bumble bees, and alkali bees can all be housed in artificial nesting sites. Since these are solitary bees, or, in the case of bumble bees, quasi-social bees, management of these species differs considerably from that of honey bees, which nest together in large colonies.
Bloom Considerations for Bees
Since bee species vary in their shapes, sizes, body strengths, tongue lengths, and flower preferences, a diversity of flowering plants is needed to satisfy them all. And, when planting, don’t forget to include plants for the 25 percent of bee species that are pollen specialists. To keep everybody happy, keep the flower show going from early spring through late fall in most regions. In subtropical or temperate desert areas, plant winter-blooming plants as well.
Bumble bee nectaring on goldenrod (Solidago species)
Bees create nests which must be provisioned with nectar and pollen to feed their brood. Some bees store nectar in their nest for adult food reserves. How they provision depends on the bee species, but in every case, it helps bees save energy when floral resources are reasonably close to their nesting site. While honey bees can fly several miles (km) and bumble bees might be able to fly a mile (1.6 km), some quite tiny bees have flight ranges of just a few hundred feet (m). Flying expends energy, so the closer food is for pollinators, the less energy they have to use.
Bee-Pollinated Flower Characteristics
Flowering plants that are pollinated by bees tend to fall into two distinct categories:
• simple, open, or bowl-shaped flowers that are relatively unspecialized (example: native roses, sunflowers)
• complicated, asymmetrical flowers that are more specialized (example: beardtongues, native orchids)
Flowers in both groups are usually blue, violet, yellow, or white; often have some scent; and are open during the day. Ultraviolet nectar guides are typically present on these flowers. The nectar quality and pollen quality will vary depending on plant species. Bees often favor flowers where the nectar’s sugars are dominated by sucrose. Pollen of bee-friendly flowers may be scented and sticky, and it must be shaken loose from a flower’s anthers by a pollinator.
Open flowers of native asters are easily accessed by bees.
Buzz Pollination
Sometimes, specialized movements by pollinators during foraging can result in more efficient pollination of flowers. Bumble bees, carpenter bees, and sweat bees use a behavior called buzz pollination (or sonication) that can loosen significant amounts of pollen. These bees contract their indirect flight muscles and vibrate their bodies, dislodging more pollen from the flower. Native plants like blueberries and cranberries (Vaccinium spp.) and shooting stars (Dodecatheon spp.), as well as tomatoes and peppers, significantly benefit from this type of pollination. While other types of bees, like honey bees, can pollinate these plants, they are much less efficient.
Bumble bee pollinating a blueberry plant (Vaccinium species)
Bee Tongue Length and Flowers
Tongue length varies by bee species and is one factor in determining which flowers a specific species can use. Long, tubular flowers found on plants such as coral honeysuckle (Lonicera sempervirens) and native delphiniums are too deep for short-tongued bees. If a bee’s tongue is too short to reach a flower’s nectar, that bee is out of luck. Long tongues are not always better, however. A long tongue may be difficult to use on shorter flowers because it does not have enough room to unfurl appropriately. Accordingly, long-tongued bees are often specialists on long, tubular flowers that are easier for them to access.
Foraging Range and Active Seasons
Foraging distances for native bees range from a few hundred feet to about a mile (about 90 m to 1.6 km), depending on the species. Small bees don’t go very far, but bumble bees can travel more than a mile (1.6 km) if resources are scarce. Flying burns calories, so it is best to keep floral resources well within reach.
Not all bee species emerge at the same time of year, nor do they have the same longevity of season. Solitary bees typically live for about a year but are active for only a few weeks. Quasi-social bumble bees may be active for several months. Those active weeks and months for bees are the critical times for finding nectar and pollen in your garden. Bloom in the garden should start in early spring and continue through late fall in most parts in North America.
European Honey Bees
In 1622, European settlers brought honey bees with them to Jamestown, Virginia. No doubt these colonists valued honey bees for their pollination services and enjoyed honey that the bees produced. Honey bees are the only insects that make a sufficient amount of honey for humans to share; beeswax and bee propolis are two other resources bees provide to us.
European honey bees can forage on many native plants, such as fragrant sumac (Rhus aromatica).
Honey Bee Management in the United States
Before honey bees were introduced, North America was solely dependent on native pollinators for pollination services. In the United States, honey bees are now managed for crop pollination and honey production. Almonds are now virtually dependent on honey bee pollination. Eighty-two percent of the world’s almond supply comes from California, the only state to produce almonds commercially, so successful pollination is critical. (The monoculture conditions of most crop production with an absence of a balanced and varied diet for bees is an ecological red flag—not to mention the ongoing use of pesticides.)
Honey Bee Characteristics
Honey bees are highly social, which is very different from native bees. A honey bee colony may have more than 50,000 individual bees. Honey bee workers are sterile females that typically live for four to six weeks. Drone bees are fertile males that usually live for one to three months. A honey bee queen may live for two to five years, possibly longer. Unlike bumble bee colonies, honey bee colonies have a perennial life cycle and persist through winter. Honey bees emerge from their hive at any time of year when the weather warms to the mid-50s°F (12 to 13°C) as long as their body temperatures are warm enough. This can be problematic outside of a growing season, when flowers are unavailable. It certainly makes a great case for planting very early- and very late-blooming plants for honey bees.
Honey Bees, Flowers, and Honey
Honey bees are generalist pollinators (polylectic) that forage on a wide variety of plants. Their tongues are of medium length, allowing them to forage on many, but not all, native plants. Long, tubular flowers or tightly closed flowers are not useful to honey bees unless they “nectar rob” by biting the base of an inaccessible flower. Native plants such as coneflowers (Echinacea spp.), milkweeds (Asclepias spp.), fireweed (Chamerion angustifolium), phacelia (Phacelia spp.), and goldenrods (Solidago spp.) are frequented by honey bees and are important sources of nectar. A general array of native wildflowers is often the basis for what is termed wildflower honey, but mono-floral honeys from plants such as blueberry, fireweed, and goldenrod are also produced.
Native trees and shrubs can be major nectar sources for honey, too, including black locust (Robinia pseudoacacia), tulip tree (Liriodendron tulipifera), basswood (Tilia americana), sumac (Rhus spp.), and raspberries and blackberries (Rubus spp.). Mono-floral honeys from several native trees are particularly delicious and highly valued; sourwood (Oxydrendron arboreum) and tupelo (Nyssa sylvatica) honeys are two notable examples.
Early-spring-blooming plants such as red maple (Acer rubrum) and willow (Salix spp.) may be good forage resources for honey bees when little else is in bloom. If weather conditions are warm enough, honey bees benefit from these plants. If the weather is cold, they may miss these blooms.
The flower traits that attract native bees also attract honey bees, with the main difference being flower anatomy. Honey bees have easiest access to more open flowers with simple structures. As with native bees, honey bees benefit from a varied diet with different sources of nectar and pollen.
Floral resources for honey bees often diminish when there are extended periods of hot and dry weather and nectar stops flowing. These periods are known as summer nectar dearths. However, nectar dearths can occur at other times of the year as well. By planting more generalist plants, especially ones that flower in summer, you can help honey bees find the food they need during difficult times. If you keep bees, you may want to include some well-behaved nonnative plants in your landscape for additional forage.
Helping Honey Bees
You don’t have to keep beehives in order to help honey bees. A Pollinator Victory Garden can provide support to managed honey bees and feral honey bees as well as native bees. Include some of the native plants that are accessible to honey bees. Trees and shrubs offer the most floral mass for large honey bee colonies. Add more bloomers for that critical time of summer dearth. And, of course, keep your garden free of pesticides. If you live near beekeepers, they will greatly appreciate the floral resources you offer in your garden. You might even be rewarded with some honey!
Butterflies
Butterflies are perhaps the most charismatic visitors to our gardens. It can be easier to convince someone to plant a butterfly garden than a bee garden, but, fortunately, both groups use many of the same plants. Of the 20,000 species of butterflies in the world, 725 are found in North America, with 575 of those species in the forty-eight contiguous states.
Eastern tiger swallowtail nectaring on Turk’s cap lily (Lilium superbum)
Butterflies are often colorful and easy to recognize, while others, specifically skippers, are frequently small, brown, and mothlike. Skippers are a subset of butterflies, accounting for about 270 of the 575 butterfly species in the continental United States. Butterflies cannot always be easily distinguished from moths, although butterflies tend to rest with their wings closed or slightly open in a V shape while moths tend to hold their wings open when at rest. Most butterflies have antennae that are club-shaped at the end, while most moths do not.
Resident and Migratory Species
Many butterfly species are local and stay local, but others migrate. Migrating butterflies that travel to some degree include painted ladies, red admirals, cloudless sulphurs, mourning cloaks, and question marks. The butterfly champion of long-distance migration is the monarch, which can travel extraordinary distances to escape cold winters.
Silver-spotted skipper on wild bergamot (Monarda fistulosa)
There are two migratory populations of monarchs in North America. Those that live west of the Rocky Mountains overwinter in Southern California along the Pacific Coast. This western population is critically endangered. Monarchs that frequent gardens in the eastern United States have evolved to migrate in the fall to Mexico, where they overwinter in a small tract of forest, which, sadly, is diminishing.
The eastern monarch population has declined by approximately 70 percent since its recorded high in the 1990s. The same individual monarchs do not travel back and forth from the east to Mexico. The first generation of monarchs are the offspring of those that have overwintered in Mexico. It takes three to four generations to travel to the northern United States and Canada. Plant milkweeds, monarchs’ obligate host plants, to help them survive these incredible odds. Once very common, the monarch is now threatened with extinction. In addition, more than twenty other species of butterflies are at risk of extinction in the United States, and many more are threatened. Get busy planting for them!
Butterfly Habitat and Life Cycle
Butterflies are mostly solitary. They do not have nests, but they shelter under twigs or tree leaves, in fallen leaves, under exfoliating bark, in brush piles, or in crevices in rocks. Leaving patches of bare soil in sunny areas, keeping some leaf litter on the ground, building brush piles, and planting in layers with plants of different heights and types will help butterflies find the habitat they need.
Monarch butterfly on swamp milkweed (Asclepias incarnata)
For butterflies and moths, larval host plants are the habitat where eggs are laid. Once the eggs hatch and caterpillars emerge, they eat the host plant’s leaves. Caterpillars grow quickly and soon sense that it’s time for their pupal stage. At that point they leave the host plant to search for a place to form their chrysalis. Most adult butterflies live for only a week or two, while an adult monarch or mourning cloak butterfly may survive for nine months or more.
Butterfly-Pollinated Flowers
Butterflies are flower generalists but do show a preference in the flowers they nectar upon, though only a few butterflies eat pollen. Butterflies appreciate a wide landing platform or a cluster of flowers, where they can easily rest while nectaring. An example of this type of flower is Joe Pye weed (Eutrochium spp.), a butterfly favorite. A landing pad is not an absolute necessity, though, if a flower is compelling and has great nectar. Blazing stars (Liatris spp.) have flowers that are spiky or button shaped and are butterfly favorites.
Flowers that particularly attract butterflies are brightly colored, usually in hues of red, orange, yellow, or purple. Nectar guides are often present, directing the butterfly to the sweet reward. Flower fragrance tends to be limited for butterfly plants, as is pollen, but lots of nectar is present. Butterflies have a long tongue (proboscis) and can access a variety of flowers. They visit many of the same flowers that attract bees.
Moths
Compared to their butterfly cousins, moths are the less-appreciated members of the insect order Lepidoptera, which includes butterflies and moths. While butterflies are active during the day, most moth species nectar at night, although some adult moths eat nothing at all. The enchanting hummingbird moth is diurnal (active during the day). This creature has the perfect common name—it has a mothlike body and flies like a hummingbird.
Many more moth species exist in the world than butterfly species—about 160,000 globally, with approximately 11,000 species in the United States. Moths are most reliably distinguished from butterflies by the placement of their wings while at rest; they hold their wings open. Although moths often have duller coloration than butterflies, there are some pretty spectacular moth species, like the cecropia, luna, and white-lined sphinx moths.
Moth Habitat and Life Cycle
Like their butterfly cousins, most moths are solitary and do not have nests. Like butterflies, moths also need larval host plants on which to lay their eggs. The caterpillars that emerge from the eggs eat the larval host plant’s leaves until the caterpillars get large enough to realize it’s time for their next life stage. They then leave the host plant and search for a place to reach their next life cycle. Some species of moth caterpillars burrow into soil or hide under dead leaves to pupate; other species form a cocoon, which they may attach to a plant.
A bird-dropping moth enjoying the nectar of silky prairie clover (Dalea villosa)
Moth-Pollinated Flowers
Moths nectar on many of the same plants that attract butterflies and bees. The most enticing moth-pollinated flowers often have a strong, sweet aroma only at night. Color does not matter as much, and flowers tend to be pale white, pale pink, dull red, or purple. There are no nectar guides, as they would not be visible at night. The flower structure often offers clusters of bloom or landing platforms. Like butterflies, moths have long tongues and appreciate plentiful nectar in flowers. Most moths do not intentionally gather pollen, so it may be more limited in moth-pollinated plants.
Beetles
Beetles are thought to be some of the most ancient pollinators. They began visiting flowering plants 150 to 200 million years ago, much earlier than bees. Beetles are also the largest group of animals on Earth, with an estimated 350,000 species globally, of which approximately 30,000 species occur in the United States. However, not all beetles are pollinators. Although few plants depend solely on beetle pollination, beetles are important pollinators of ancient plant species such as magnolias (Magnolia spp.), spicebushes (Lindera spp.), and water lilies (Nymphaea spp.).
Flower longhorn beetle eating pollen
Beetles move slowly and cannot visit as many flowers as some other pollinators, making them less effective than other pollinator groups. Even so, pollinating beetles have hairy bodies that catch pollen, and they manage to get the pollination job done. Some beetle species feed on both nectar and pollen, but others feed only on pollen, so the plants that attract them typically have lots of pollen and usually some nectar (although no nectar guides are present). Beetles may also eat flower petals and other flower parts.
Common beetle pollinators include flower long-horn beetles, soldier beetles, leaf beetles, pollen beetles, and tumbling flower beetles. The habitat that pollinating beetles need matches the habitat you create for bees and butterflies.
Beetle-Pollinated Flowers
Although beetles see colors, they rely on their sense of smell to find flowers. Beetle-pollinated flowers are often dull white or green, and based on the flowers they visit, maroon appears to be attractive to them as well. Beetles nectar from flowers of other colors if they are drawn by the scent. Strong, fruity, or fetid odors appeal to beetles. Open flowers and bowl-shaped flowers are the easiest for beetles to access.
Flies
Flies are a large and diverse group of insects with varied feeding habits. Nearly half of all fly families visit flowers to forage on nectar and/or pollen, but not all are effective pollinators. Some of the common species of pollinating flies include bee flies, tachinid flies, thick-headed flies, and hoverflies.
Hover fly nectaring on sneezeweed (Helenium autumnale)
Hoverflies
Hoverflies, also known as flower flies or syrphid flies, are an important group of fly pollinators. The adults are well equipped for pollen feeding and rely almost exclusively on flowers for their food. They get one of their common names from their ability to briefly hover over flowers. There are many hoverfly species, about six thousand globally. Often resembling bees or wasps, hoverflies have only one pair of wings, compared to the two pairs of wings on wasps and bees.
Some hoverflies have a modified mouthpart, similar to bees, through which they sip nectar. Hoverflies are typically flower generalists and highly efficient at pollination. As a bonus, the larvae of most hoverflies are natural enemies that prey on soft-bodied insects such as aphids.
Bee Flies
Bee flies are important fly pollinators. They’re intriguing creatures with hairy, fuzzy-looking bodies, enabling them to collect a great deal of pollen. In contrast to shorter-tongued flies, bee flies have a long tongue and access nectar from flowers with longer corolla tubes. They can hover over flowers for short periods of time like hoverflies.
Fly-Pollinated Flowers
Pollinating flies are attracted to flowers that are dark brown or purple, or sometimes pale or white. They nectar on plants of other colors as well. The flower scent most appealing to flies is a putrid smell, an odor akin to rotting flesh, though they visit less-odoriferous flowers as well. Nectar may or may not be present in fly-pollinated flowers, but there are no nectar guides. The flowers they choose do have some pollen.
Habitat for pollinating flies should include an abundance of insects attracted by a diversity of native plants. Some of these insects, especially aphids and spiders, serve as food for hoverfly larvae. For fly egg-laying requirements, include a natural area in your landscape with fallen logs and leaf litter.
Wasps
Not many people get excited when they hear about gardening to support wasps. The truth is, wasps are valuable insects in the landscape, particularly as predators and parasitizers of insect pests. Bees have descended from wasps and are in the same order of insects (Hymenoptera), so wasps and bees have similar life cycles and nesting behaviors.
Great black digger wasp foraging on mountain mint (Pycnanthemum species)
Wasps often look like bees but usually don’t have the same fuzzy hairs on their bodies that enable bees to pick up pollen. This means that less pollen sticks to their bodies, limiting their effectiveness as pollinators.
Solitary vs. Social Wasps
Social wasps are the insects that people usually think of when it comes to wasps, such as paper wasps and yellow jackets. These insects nest in colonies, some in the ground and some in structures they build. Solitary wasps make up the preponderance of wasps and nest alone in the ground, in pithy plant stems, or in structures they create with mud. Both social wasps and solitary wasps visit flowers for nectar.
Parasitic wasps (parasitoids or parasitizers) are solitary and have a fascinating lifestyle, in a gruesome sort of way. They lay their eggs in or near the bodies of other insects. Once the wasp larvae emerge, they eat the body of their insect host. Parasitic wasps are important beneficial insects with a well-earned reputation as garden allies.
Wasp-Pollinated Flowers
Wasps require a habitat that has areas to nest in and an abundance of insects to feed their young. They are terrific predators; during their larval stage, wasps are carnivorous, eating insect prey collected by their mother. When wasps become adults, they visit flowers for nectar, but some are also carnivorous. Wasps have short tongues and need more open, accessible flowers than bees need. They are attracted to many of the same flowers that attract butterflies.
Hummingbirds
Hummingbirds are what come to mind when pollinating birds are mentioned. In fact, more than fifty species of birds in North America drink nectar, including Baltimore orioles, yellow-bellied sapsuckers, scarlet tanagers, and Tennessee warblers. But hummingbirds garner the most attention. These captivating creatures dart through our gardens like speeding bullets, feisty and very entertaining. More than a dozen hummingbird species summer in the United States, including ruby-throated hummingbirds, Rufous hummingbirds, and Anna’s hummingbirds.
Ruby-throated hummingbird nectaring on coral honeysuckle (Lonicera sempervirens)
Hummingbird Habitat
Hummingbirds need a number of resources as habitat that you can provide, including tubular flowers loaded with nectar, smaller trees and branches to nest in and perch on, materials like spider webs and lichen to form nests, a source of clean drinking water, and an abundance of small insects as a source of protein.
Hummingbird-Pollinated Flowers
Hummingbirds are attracted to large funnel- or tubular-shaped flowers that accommodate their long tongues. Their tongues are so long that when they’re retracted, they coil up inside the birds’ heads, around their skulls and eyes! Hummingbirds prefer red flowers but will feed from flowers of other colors when needed. Since birds have no sense of smell, a hummingbird’s chosen flowers typically have no scent. There are no nectar guides on flowers that appeal to hummingbirds, but there is a lot of nectar and some amount of pollen.
Hummingbirds are particularly attracted to red flowers, such as cardinal flower (Lobelia cardinalis).
Bats
Across the globe, approximately 530 species of flowering plants rely on pollinating bats as their exclusive or major pollinators. Of the estimated 1,300 species of bats worldwide, about fifty bat species feed only on nectar or on nectar and pollen. Some bat species are omnivores that feed on fruit and insects as well as nectar.
Lesser long-nosed bat nectaring on agave flower (Agave species)
Most bat species that pollinate flowers are found in tropical and subtropical areas of the globe. Bats pollinate more than 300 species of fruit, including bananas, mangoes, and guavas. Some pollinating bats can be found in desert areas like the Southwestern United States and Mexico, where they are crucial pollinators of agave, saguaro cactus, and organ pipe cactus.
Only three species of nectivorous (nectar-feeding) bats reach the United States in the most northern part of their range. These include:
Mexican long-nosed bat (Leptonycteris nivalis)
• Federally listed as endangered
• Migrating species
• Range: Small areas in New Mexico and Texas; also in Mexico, Honduras, and Guatemala
• Habitat: Desert scrub, open conifer-oak woodlands, and pine forests
• Pollinates: Agave flowers are this bat’s primary food source. It also feeds on the flowers of cacti, some subtropical trees, and other plants.
Lesser long-nosed bat (Leptonycteris curasoae yerbabuenae)
• Recently delisted as endangered
• Migrating species
• Range: Parts of Arizona; also in Mexico and northern South America
• Habitat: Semi-arid or arid environments near cacti
• Pollinates: Columnar cacti like saguaro and organ pipe cactus, agave, some tropical trees and shrubs, and other plants
Mexican long-tongued bat (Choeronycteris mexicana)
• Not endangered
• Somewhat migratory
• Range: California, Arizona, New Mexico, Texas; also in Mexico, Central America, and northern South America
• Habitat: Desert, montane, riparian, and pinyon-juniper woodland
• Pollinates: Mostly agave and columnar cacti
These three bat species typically spend the winter in caves in their southern range and migrate north in the spring and summer to the Southwestern United States. Their migration to and from the U.S. coincides with the flowering of agave and columnar cacti, with which they have mutualistic relationships. As populations of agave and cacti diminish, these bat species are also threatened. The cutting of agave buds for tequila production reduces the nectar sources for these bats. If you live in the Southwestern United States, consider planting agave and columnar cacti in your landscape.
In general, flowers that attract pollinating bats are large; dull white, green, or purple; open at night when bats are active; and have a highly fragrant, fruity or musty scent. Bat-pollinated flowers contain a lot of pollen and dilute, abundant nectar; they do not have any nectar guides.
Pollinating bats may also visit hummingbird feeders, especially when the flowers they need are not in bloom. These thirsty nectivores can drain a feeder overnight. If you reside in an area frequented by these bats, add some extra hummingbird feeders during their active season. Since artificial nectar does not provide all the nutrients or pollen that bats may need, make sure to include their required plants in your landscape as well.