You may have read or heard news reports about the declining populations of native pollinators, such as bees, butterflies, moths, hummingbirds and others. It appears that the problem is complex, and multiple factors are at work. But much of the decline in populations can be attributed to habitat loss, disease and parasites, pollution and pesticides.
Particularly dramatic have been losses in commercial hives of European honeybees. This non-native bee species plays a critical role in the production of many crops, such as peaches, pears, apples, citrus and almonds. Bees are important in many vegetable crops, both for production and to create the seeds needed to grow succeeding crops. Factors such as frequent transportation, agricultural pesticides, poor diet and issues with parasites have been identified in hive losses known as colony collapse disorder.
A home gardener can do little to affect the loss of commercial honeybee hives. We can, however, help support native pollinators by creating pollinator-friendly landscapes and pollinator gardens, as well as protecting wildlife habitat.
Pollination in plants occurs when pollen from the male parts of flowers is transferred to the female parts of flowers and fertilizes the eggs. This results in fruit containing seeds. The flowers of some plants are able to carry out this process without any help from pollinators. The structure of tomato flowers, for instance, allows them to be pollinated even if not visited by bees. Many trees and all of the grasses are wind pollinated and do not make use of pollinators. They release pollen into the air and allow the wind to carry it to the female parts of other flowers.
A large number of plants, however, rely on various animals to transfer pollen from flower to flower. Pollinators include many types of insects, particularly bees, butterflies, moths, beetles, wasps and even some flies. Hummingbirds also help carry out pollination of plants in Louisiana. In desert areas, bats play an important role in pollination, but not here in Louisiana. To ensure pollination, these plants produce showy flowers to attract pollinators to the blossoms and provide nectar to reward them. Some pollinators, notably bees, also collect some of the pollen for food.
The flowers of plants that use pollinators have evolved to attract and use particular pollinators. Flowers are structured to ensure pollination from the correct pollinator and may exclude others. Plants that produce long, tubular flowers are generally pollinated by hummingbirds, butterflies and moths, which are able to access the nectar with their long tongues. Open-faced flowers and those with short flower tubes make nectar available to short-tongued bees. Bees, however, will sometimes crawl to the base of a long-tubed flower and chew a hole in base of the tube to access the nectar without pollinating the flower.
If the flowers of plants are not pollinated, they will not produce seeds and fruit. In nature, this may prevent a species from properly reproducing and maintaining its population. Many native birds and mammals feed on the fruits and seeds that result from pollination. So food supplies for many native animals may be affected if low populations of pollinators prevent proper pollination.
We can use our landscapes to provide food and shelter for pollinators and help increase their populations in a variety of ways.
When choosing landscape plants, such as trees, shrubs, ground covers, vines, perennials and bedding plants, keep pollinators in mind. Choose native species when you can, but do not overlook non-native species. Look at the time of blooming, and choose plants that bloom at various times of the year, from spring to fall and even in winter.
When it comes to selecting trees, many popular shade trees, such as oak, maple, elm and pine, are wind pollinated. Be sure to also include flowering trees such as native magnolias, dogwood, crape myrtle, native hollies, American fringe tree, redbud, black cherry, American persimmon and loquat.
Many flowering shrubs are also available, both native and non-native, that provide colorful flowers for our landscapes. Choose a variety of shrubs that bloom at different times of the year. Avoid varieties that have highly double flowers with many petals. Rather, choose those with single or semi-double flowers because they provide more nectar and pollen.
Flowering vines also may be planted for pollinators. Vines like coral honeysuckle, cross vine, yellow jessamine, American wisteria and coral vine bloom at various times and are attractive to a variety of pollinators
Beds in your landscape may be dedicated to planting perennials and bedding plants that provide food to pollinators. Pollinator gardens are generally attractive and colorful due to the use of abundantly flowering plants. Diversity is key when planting pollinator gardens. Choose a wide variety of plants that produce flowers of many different shapes, colors and sizes to attract the greatest diversity of pollinators. Also, choose perennials and bedding plants that bloom at different times of the years. Cool-season bedding plants, grown from October to May, will even provide flowers during winter, when bees and other pollinators may forage on mild days.
Gardeners have long created gardens for butterflies and hummingbirds. Many of the flowers fed on by butterflies and hummingbirds will attract bees and other insects. The many kinds of salvias so commonly used in butterfly and hummingbird gardens will also attract bees. When planting to attract more types of pollinators, also choose flowers that are easy for bees to feed on, such as the clovers (white and crimson) and members of the aster family, (daisies, sunflowers and zinnias).
You may also provide larval food plants for butterflies. Butterflies lay eggs only on certain plants, which vary depending on the species of butterfly. Monarch caterpillars will only feed on milkweed plants, and Gulf fritillary caterpillars prefer species of passion vines. The parsley worm, which grows up to be the Eastern black swallowtail, feeds on parsley, dill and fennel. Sulfur butterflies lay their eggs on cassias, while bean leaves are the preferred food of long-tailed skipper caterpillars.
If your property is large enough, you may dedicate an area to a wildflower meadow planting. A blend of native wildflower seeds, both annual and perennial types, may be planted in that area and allowed to grow to create a more natural habitat for pollinators.
The use of pesticides is detrimental to pollinators and should be kept to an absolute minimum. Many landscape insect and disease outbreaks of trees and shrubs will clear up on their own without treatment with pesticides.
Learn to tolerate some damage to landscape plants. For example, leaf cutter bees will cut circular pieces of rose leaves about the size of a dime or nickel. Although unsightly, this damage does not greatly affect the health or blooming of the roses, and treating with an insecticide will kill this helpful pollinator.
A list of native plants attractive to pollinators is very helpful when considering what to plant. The Pollinator Partnership offers planting guides tailored to specific ecoregions. The Selecting Plants for Pollinators guides have excellent information on pollinators and provide extensive lists of native plants. To get the guide specific to where you garden, visit the Pollinator Partnership website at www.pollinator.org. Click on Plant Guides, and then enter your 5-digit zip code. The regional guide you see will have charts that list which native plants grow best in your area so that you can plant them to attract more pollinators to your gardens.Dan Gill is a consumer horticulture specialist in the School of Plant, Environmental and Soil Sciences.
Coral honeysuckle. Photo by Dan Gill
Loquat. Photo by Dan Gill
Salvia. Photo by Dan Gill
Gulf fritillary adult butterfly feeds on nectar from lantana flowers. Photo by Kathy Kramer
Monarch caterpillar feed on Mexican milkweed leaves. Photo by Kathy Kramer
Monarch butterfly on Mexican milkweed. Photo by Kathy Kramer