Pollinator Management

• Bees recover slowly from pesticide spraying. It may take 3 or 4 years for populations to reach their former levels.
• To protect pollinator populations, no more than one-third of a habitat should be mowed or burned in any given year.
• How far a pollinator can fly is an important consideration for habitat restoration and management. Solitary wild bees generally have maximum foraging ranges of between 150 and 600 meters. (492 to 1,969 feet). Larger bees can fly farther than smaller ones.
• If the distance between the suitable habitat patches along a pollinator’s migration route is too great, smaller or weaker individuals may die during their journey.

Different pollinators visit different flowers, depending on their size, the length of their tongue, their color vision, their sense of smell, and other factors. Therefore one of the most effective things you can do to promote healthy and diverse pollinator populations is provide a variety of flowering plants.

What to Plant

• Although native plants are great, note that some non-native garden plants and even common weeds are important foraging resources for generalist pollinators where natives are absent. However, some pollinators feed only on specific native plants. For overall ecosystem health, native plants typically have a higher conservation value. According to the Metropolitan Flora Project, an initiative of the Brooklyn Botanic Garden, over 50 native plant species are locally extinct or nearing elimination from the New York metropolitan region. It is more important than ever to conserve native plants and their pollinators in urban areas whenever possible. 
• Plant large drifts or clumps of flowers of the same species rather than scattering them here and there throughout landscape. Most bees tend to forage on one species at a time — which is better for the plant, too, as it ensures that the pollen will be spread among plants of the same species. Keeping food resources close together also makes it easier for bees to find pollen and nectar and get back to provision their nest without expending energy traveling great distances, as does providing the flowers they need in close proximity to their nesting habitat.
• To ensure a steady food supply for resident and migrating pollinators, it’s also important to have plants in flower from April through October.

Bee Flowers

Bees can see a wide range of colors, but primarily those at the blue end of the spectrum, including ultraviolet. For this reason, the flowers they favor are typically shades of blue and purple, but also white or yellow. Bees can recognize pattern as well as color, and the flowers they visit frequently have “nectar guides” on their petals—radiating lines or concentric circles, often UV, that guide the insect into the flower. In addition, bee flowers are often sweetly fragrant.

Some flowers, like our native blue lupine, are particularly suited for pollination by bumble bees, with modified lower petals that serve as sturdy landing pads. Other commonly recommended bee plants (for the eastern USA) include blue lobelia, blueberries, sweet pepperbush, and blazing stars. For more plants, see the Xerces Society publications for Bees in your region.

Although the vast majority of bees are generalists that feed on a wide variety of flowers, depending on the location, roughly 20 percent feed on species in only one plant family, or even a single species. For information on the plants favored by these specialist bees, see here.

Butterfly Flowers

Butterflies are attracted to many colors. The flowers they visit for nectar are usually found in clusters to provide a good landing platform for the butterflies, which walk around on the flower clusters probing for nectar with their strawlike tongues. Butterfly blooms have a floral tube that is tailored to the length of the particular species’ tongue.

Butterflies have a weak sense of smell, and the blooms they visit are typically odorless.

Some native nectar plants for butterflies in the eastern USA include New England aster, mountain mint, goldenrods, and joe-pye weed. The North American Butterfly Association website has a list of native garden plants that are good for butterflies.

Moth Flowers

Nocturnal moths and other night-flying pollinators are attracted to white or pale-colored flowers that are visible in the dark; in fact, some of these blossoms open only at night. The flowers often have deep tubes to match the length of the moth’s tongue. Because the moths hover, the flowers they feed on have no landing platform.

Moths have a great sense of smell, so the flowers they favor have a strong, sweet scent, especially useful for luring pollinators at night.

Native plants in our region that are pollinated by moths include sacred datura and evening primrose.

Hummingbird Flowers

Most birds can see the same colors as humans, but hummingbirds tend to favor red or orange blooms. The flowers are typically long and tubular, adapted for a hummingbird’s long, narrow bill and tongue, and they often (although not always) point downward so that the hovering hummingbirds have easy access.

Because hummingbirds, unlike many insects, have a poor sense of smell, the flowers they visit usually are not fragrant.

Wild columbine, cardinal flower, red bee balm, and coral honeysuckle are a few hummingbird-pollinated native plants. A longer list of plants is here. 

Fly Flowers

Flies can see a wide range of colors, but primarily whites and yellows. Some, like syrphid flies, look a lot like bees and visit bee flowers. Other flies pollinate early spring wildflowers, fancying brown or purple blossoms that resemble rotting flesh and emit the essence of carrion or dung. Among the preferred flowers of these flies are the aptly named skunk cabbage, which has a mottled purple bract called a spathe that partially surrounds tiny flowers massed together along a fleshy pole called a spadix. Other arums such as jack-in-the-pulpit, red trillium (called “stinking Benjamin” by early naturalists), and pawpaw are also native fly-pollinated plants.

Special Food Resources        

Some butterflies, such as commas and mourning cloaks, are attracted to rotting fruit and will feed on watermelon or banana pieces placed outside in summer. (This may also attract wasps.) See the NABA website link for details on butterfly feeders. 

Many pollinators require water or mineral salts, so providing areas of moist soil can be beneficial. One easy way to do this is by placing a water-filled plastic gallon jug with pin pricks in bare soil. 

Tips for Gardeners

Before getting into specifics on providing food resources and meeting other pollinator needs, it’s useful to consider actions that restore or maintain habitat quality in general. While it is important to look at management within individual gardens, parks, or natural areas, it is also helpful to step back and look at habitat availability in the larger landscape. This is important because many pollinators do not use just one habitat patch but rather “commute” across the landscape looking for floral patches. For example, some large-bodied bees such as bumble bees and honey bees can fly over 1 kilometer (.6 mile) from their nest, so they potentially can visit multiple green spaces to forage from flowers. Other bees fly shorter distances from the nest and may be influenced by factors at a smaller spatial scale. Butterflies also vary in mobility, using small habitat patches transiently to refill on nectar as they move through developed landscapes.

Restore Early Successional Habitats

The best pollinator habitats in our region are so-called early successional habitats such as meadows or old fields with a diversity of flowering plants. Protecting and restoring remnant serpentine and calcareous grasslands, pine-oak barrens, and wet meadows may be important for protecting populations of rare pollinators. In areas where these habitats have become overgrown, it is often beneficial to mow periodically to prevent them from reverting to forest. Removing invasive non-native shrubs such as Tartarian honeysuckle, autumn olive, and multiflora rose that quickly encroach on a diversity of good nectar sources is also important, as is supplementing these habitats with additional native plantings. Transitional habitats such as forest edges with plenty of nesting habitat for wood-nesting bees or ground nesters should also be restored and protected.

In addition, there are pollinators that are dependent on forest habitats, such as forest butterflies and early spring bees, who forage on willow and cherry trees as well as ephemeral wildflowers like spring beauty. Pollinator conservation and management on the landscape scale should include habitat for these species.

In many parts of North America, managing deer populations is essential to maintaining habitat quality. Although white-tailed deer are native to the region and fascinating animals, their numbers have increased to the point that they are overbrowsing natural habitats and damaging farms and residential gardens.

Deer often selectively browse on flowering plants that are a critical resource for pollinators. Working with municipalities and state wildlife agencies to manage deer numbers is an important component of pollinator habitat management.

Fire is an essential natural process for maintaining habitat quality in some parts of the metropolitan region, especially the serpentine barrens and pine barrens of New York and New Jersey. When fire is suppressed in these areas, natural open habitat and associated plant and animal species are lost, including important pollinator habitat. Prescribed fire (fire that is safely and carefully used in appropriate areas) can help maintain open habitat. Although fire is a vital management tool, it is best to burn only a portion of a habitat each year, leaving refugia for pollinators and other wildlife in the remaining areas.

Create or Maintain Habitat Corridors Through Developed Areas

Sometimes one habitat provides everything a particular insect pollinator needs to complete its life cycle. Other times more than one habitat is necessary to meet special needs for food or nesting. In developed areas these patches are often separated by inhospitable habitat that insects cannot cross, and it’s important to connect them.

When properly managed, roadsides can be effective corridors in urban and suburban landscapes. Allow flowering “weedy” species to grow along the roadways, and add native nectar- and pollen-producing plants. Research has shown that a healthy population of nectar plants will keep pollinators busy foraging on the side of the road and out of passing traffic.

Common areas of condominiums and housing developments can provide additional linkages when they are managed as pollinator habitat rather than lawns.

Playgrounds, parks, and schoolyards are other places that can be managed to provide critical habitat connectivity for pollinators.

Not every pollinator has the same nesting requirements. Following are some tips on how to provide nesting sites for a variety of pollinators. Keep in mind that nesting habitat for bees as well as egg-laying habitat for butterflies, moths, and other insect pollinators should be located close to good foraging habitat.

Native Bees

Ground nesters

To provide nesting habitat for ground-nesting bees, maintain areas of bare or sparsely vegetated soil. Ground-nesting bees prefer loose, well-drained soil in a sunny spot. Some species nest in flat areas, while others prefer earthen banks, so provide a variety of areas with different slopes if possible, preferably south-facing to maximize exposure to the sun. In areas with healthy, friable soil, clear an area of vegetation at least several yards across. In places where the soil is compacted or otherwise unsuitable, dig out a section 2 to 3 feet deep and replace with sandier loamy soil that is soft enough to dig in but stable enough that burrows won’t collapse. Potential nesting habitat can also be provided with soil-filled planters. Once you have established a nesting area, make sure it does not become overgrown with vegetation or shaded out. To prevent the soil from becoming compacted, do not walk over the area, and do not till or dig it up as that will destroy the nests.

Cavity nesters

Protect nesting sites for wood-boring bees by keeping dead trees, snags, or fallen logs on the land. Some bees will build their nests in old beetle tunnels. In addition, minimize pruning of pithy shrubs, such as elderberry, sumac, or hydrangea from year to year.

Artificial nest sites

In areas where there does not seem to be sufficient natural habitat, you can provide a variety of nesting materials that bees will use. The Xerces Society pdf, Nests for Native Bees includes plans for the following nest types.  

Bee nesting blocks: Some cavity-nesting bees will use manmade nesting blocks, including the blue orchard bees used commercially to pollinate apple orchards.  To construct a nest block, use preservative-free wood—4x4s are adequate for blocks with only small nesting holes, but 4x6s are required for larger nesting holes. You can also drill various-sized holes in stumps or old logs.

Making holes of varying depths and diameters in the nest block is often recommended to attract a variety of bee species. There is no “correct” way to do this, so it’s worth experimenting to see what you get.  Nesting holes should be relatively small: 3/32 to about 3/8 inch.  Holes 1/4 inch or less should be 3 to 5 inches deep, while holes larger than 1/4 inch should be 5 to 6 inches deep. The block must be closed at one end and holes should be smooth and placed in from the edge at least 3/4 inch.

Be sure to locate the nest block where it is protected from direct rain and faces south or southeast so it is warmed by the morning sun. Place the block on a firm support 2 to 6 feet above the ground. Bees use landmarks to navigate to and from their nest, so putting the nest block near a large object (like on a shed or tower) will help them navigate.

Stem bundles: You can also bundle pithy, soft-centered stems together in small packets. Good plants to use include sumac, box elder, elderberry, raspberry, and even phragmites, Japanese knotweed, or old bamboo plant stakes—anything with hollow stems. Cut sections just below a node, place them so that the open ends all face in the same direction, and strap them together. Hang the bundles outside in a sheltered location horizontal to the ground, facing the morning sun.

Bumble bee nesting boxes: Bumble bees, which naturally seek out old underground rodent nests or cavities under grassy tussocks, may find specially constructed boxes suitable for nesting. Typically, they are made of wood and filled with nesting materials such as dried moss or horsehair stuffing from old furniture. It’s not clear how well these artificial nests actually work, but building one can be a fun student project and help raise awareness about the needs of bumble bees and other native pollinators.

Care of artificial nests

Nesting blocks and boxes as well as stem bundles should remain out during the season but can be brought into a protected area for the winter. To prevent disease transmission, make sure you clean out nesting boxes or bundles after the new bees emerge in spring, or replace them each year.

Butterflies and Moths

To provide egg-laying habitat for local butterflies and moths, you need to become familiar with the food plants required by their larvae. The caterpillars of each species have specific host plants. Although adult spicebush swallowtails nectar on many different flowers, for example, their caterpillars feed mainly on the leaves of spicebush (Lindera benzoin). The North American Butterfly Association website has a good list of caterpillar plants for butterflies. 

Another excellent resource is Caterpillars of Eastern North America:
A Guide to Identification and Natural History by David Wagner. 

Butterflies and moths lay their eggs directly on their larval food plants, so make sure these species are in close proximity to nectar sources for adults. Occasionally, butterflies and moths will pupate on their food plant, but often they move to another sheltered location or in the leaf litter to pupate. Maintain undisturbed habitat nearby where the caterpillars can safely pupate before emerging as adults.

Insect Pollinators in General

To retain a diversity of nesting materials, avoid excessive raking and manicuring.

Different bee species use different materials to construct the brood cells in which their young develop and to seal nests.  For example, leaf cutter bees may use bits of leaves from various shrubs, while other bees may use mud or fine pebbles.

Ruby-throated Hummingbirds

After spending the winter as far south as Central America, the Ruby-throated Hummingbird returns north to nest. Their tiny nests are constructed of plant fibers and lichen woven together with spider silk. Like bees and other insect pollinators, they require feeding and nesting habitats in close proximity. Ruby-throated Hummingbirds are found in a variety of habitats, but according to the recent New York State breeding bird atlas, they rarely nest in heavily developed areas. 

Tips for Gardeners

Insect pollinators can spend the winter in a variety of life stages (egg, larva, pupa, or adult) and this varies, depending on the species. Most native bees spend the winter in their nest cells as pupae, emerging as adults the following spring or summer, so it is critical to protect nesting areas from disturbance all year long, not just during the nesting season. One exception is bumble bees, which do not overwinter in their nests. Instead, new bumble bee queens emerge from their natal nest in the fall and search for overwintering sites, burrowing into leaf litter or loose soil. It is just as important to provide sheltered areas for them.

Butterflies and moths also overwinter in a variety of stages (egg, larva, pupa, adult). For example, Mourning Cloak butterflies overwinter as adults, while Eastern Tiger Swallowtails spend the winter as a chrysalis.

All need sheltered areas in which to spend the winter. To provide these safe havens, set aside undisturbed patches of habitat allowing leaf litter, standing dead twigs/stems, or other ground cover to remain. Do not till soil where there might be ground nests. “Wild,” unmanicured locations will provide the protected nooks and crannies that pollinators and other animals need for survival.

Land mangers, urban farmers, and home gardeners are often faced with pest control decisions, including whether to use chemicals and if so, which ones to apply. Although pesticides are commonly used and considered a method of choice by many, they are harmful to bees and other insect pollinators.

Insecticides can kill directly as poisons enter a pollinator’s body by penetrating its integument (“skin”), or when it ingests poisoned nectar and/or pollen grains. Slow-acting poisons in pollen and nectar brought back to bee nests can ultimately kill the developing larvae. In other cases, pesticides do not kill the insect outright, but rather affect its ability to fly, navigate, or conduct other activities important to survival.

Herbicides used to kill weeds are also detrimental to pollinators, often removing flowering plants that native bees and other pollinators rely on. For example, dandelions, red and white clover, and plantain are all common lawn “weeds” that can provide substantial nectar and pollen for bees and other pollinators.

Least Toxic Approaches

To minimize impacts on pollinators, it’s important to avoid the use of chemical pesticides if possible. Instead, use one of two proven systems to control pests: organic growing or integrated pest management.

• Organic growers refrain from using synthetic pesticides and instead promote and enhance natural diversity and biological cycles to make a garden or farm as self-sufficient as possible.
• Integrated pest management employs many of the same practices as organic growing, but does not rule out synthetic pesticides as a last resort. A systematic process, IPM involves prevention, monitoring, and choosing the least toxic pest control when action is necessary.

Both IPM and organic growing include measures such as using lures and baits that help monitor pest populations and even attract them away from plants without the use of chemical pesticides. Selecting pest-resistant plants is another basic preventive practice.

Among the many other tools of a least-toxic approach to pest management is maintaining diverse habitat for beneficial insects such as lady beetles and assassin bugs, which prey directly on pests. Other beneficials are parasitoids, such as parasitic wasps, which develop in or on pest larvae, ultimately killing them to help keep populations in check. Recent studies indicate that daisy-like native flowers such as asters and coneflowers, along with culinary herbs such as dill and parsley that produce inverted parasol-shaped inflorescences, are best at attracting these beneficial insects. Many also provide nectar and pollen for pollinators. For more information on beneficial insects, see here. If chemical pesticides are necessary, they should be applied in the evening or at night when most pollinators are not actively foraging.

Wildlife migration, the periodic seasonal movement of birds or other animals from one geographic region to another, is usually related to available food supplies or breeding season. In the eastern USA, the most common pollinating bird species is the Ruby-throated Hummingbird, which migrates each spring from as far south as Panama to as far north as Canada, with a return trip south in the fall. During the long flight, they stop frequently to rest and refuel before continuing on their way. Urban parks, natural areas, and even gardens are critical stopover habitats for migrating birds.  

Stopover habitat in urban landscapes is also important for migrating butterflies such as Monarchs and Painted Ladies. For example, New York City is located along the Atlantic Flyway, a major transit route for thousands of birds and butterflies in the fall and spring.

Management Tips

• Make sure your landscape includes nectar plants to fuel migrants’ spring and autumn journeys. The last stragglers fly south from their breeding grounds in northern latitudes until as late as November, so be sure to grow plenty of late-blooming species such as asters and goldenrods.
• Participate in the Monarch Waystation Program to provide stopover habitat for the butterfly’s epic seasonal journeys. An easy way to establish a new Monarch Waystation is to order a Monarch Waystation Seed Kit developed by Monarch Watch. Each kit includes nine seed packs, including milkweeds and other nectar plants.