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Pollinator Educator: Urban Pollinator Conservation Series @ LSU

Pollinator Gardening in Louisiana
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Pollinators are animals that transfer pollen from one plant to another. They are essential for the production of many crops and wildflowers. The honey bee is arguably the most important, but bumblebees, solitary native bees, butterflies, moths, flies and even beetles can also serve as pollinators. Pollinator declines have gained much attention in recent years, and concerned citizens wonder about what they can do to help. Fortunately, establishing pollinator gardens in your community will go a long way towards sustaining these important and beneficial insects!

Common garden visitors. North America alone is home to over 4,000 species of native bees that vary in size from tiny Perdita to the easily recognizable carpenter and bumblebees. Louisiana has over 200 bee species! While some are distinguished by yellow, orange or red stripes, others range in color from all black to metallic blues and greens.

Providing habitat around your home to support our six-legged friends will benefit more than just pollinators—healthy gardens support many other insects too. Natural enemies (predators and parasitoids) like green lacewings, ladybugs, spiders and solitary wasps are attracted to flowering plants and are great at controlling common garden pests without the need for insecticides. Hover flies, often mistaken for sweat bees, even have a predaceous larval stage. You might spot cuckoo bees that parasitize the nests of other bees. This may seem like a bad thing, but diverse insect communities are a sign of a healthy ecosystem and a healthy garden!

Considerations when choosing plants. Bees provision their nests with pollen to feed to their young in the spring, while butterflies sip nectar as they search for host plants to lay their eggs. Not all plants are equally good at producing pollen and nectar, so planning your garden to have good sources of both throughout the year is important. Many common ornamental plants are selected for showy flowers at the expense of nectar and pollen production. Choosing native and heirloom varieties will ensure that pollinators benefit from your garden.

Some species of bees specialize on one type of flower, like the Southeastern blueberry bee, while others are generalists and can feed on many types of flowers. Provide a variety of floral shapes, sizes, and colors to attract the greatest diversity to your garden. Group plantings of a species together to create bold color statement, which will also help pollinators locate your garden. Seeds of zinnia, cosmos and Shasta daisy are an inexpensive way to cover a large area in blooms throughout the summer. Be sure to check with us to identify plants that will work best in your garden.

Edible landscaping. Not all pollinator habitats need to be ornamental. Consider this: one in every three bites of food we eat relies on pollination. But we aren’t the only ones to benefit from this interaction—plants produce nectar and pollen specifically to attract pollinators. A 100 sq. ft. vegetable garden can produce hundreds of pounds of produce in a summer! If this seems daunting, consider an herb garden—flowering borage, lavender, rosemary and basil also benefits pollinators. Citrus or pecan trees in southern Louisiana can double as shade trees, and blueberries, which are native to the region, can be trained as hedges.

Nesting habitat. Honey bees travel many miles from their hives in search of food, but the majority of native bees only travel a few hundred feet from their nests. Providing habitat for nesting is therefore essential to ensuring native bees come back to your garden year after year. “Bee hotels” (or bed-and-breakfasts when combined with a garden!) can serve as a focal point and give children a safe and up-close look at nesting behaviors of our native stingless bees. These can be easily constructed using recycled garden materials. Be sure also to leave patches of soil free from mulch or pine straw, since 70% of native bees nest in the ground.

Conserving Pollinators with Edible Landscaping

Not all pollinator habitats need to be ornamental, and readjusting our notions of aesthetics opens the door to a world of gardening possibilities! Edible landscaping has the added benefit of providing nutritious and locally sourced food for the home gardener while providing much-needed resources to local pollinators. This is particularly important in urban areas, which often have fragmentation of native pollinator habitat. Networks of private and public gardens, both ornamental and edible, can provide considerable conservation and biodiversity benefits for pollinators throughout the area.

Pollination is a service provided by native and managed bees that is essential for the production of many crops. In fact, one in every three bites of food we eat relies on pollination. This includes some of the most nutritious components of our diets, such as fruits, vegetables and nuts. Even though pollination may not be directly necessary for a plant to produce the part that we eat, such as carrots, onions and other root vegetables, pollination is needed to produce the seeds that will grow into more plants.

But we are not the only ones to benefit from the interaction of pollinators with flowering crop plants. Edible crop plants produce pollen and nectar specifically to attract their pollinators. Commercial agricultural operations rely heavily on honey bees for crop pollination, but a number of native bees are more efficient crop pollinators. Providing these plants in your home garden enhances urban pollinator habitat while allowing you to enjoy the freshness and flavor of home grown produce, as well as savings on grocery bills!

Design considerations. Most fruits and vegetables require 6-8 hours of sun a day to produce well, so site selection is an important first consideration. When arranging plants, be sure to account for final plant size, since many vining varieties, like cucumbers or melons, will spread over a large area. If space is limited, provide structures so plants can be trained to grow vertically, or consider compact varieties. Growing your own produce also provides the opportunity to experiment with heirloom or unusual varieties that may not otherwise be available in grocery stores. With these you can mix beauty and utility in both vegetable and flower gardens. Leafy greens come in many colors and textures and can be incorporated along borders. When left to bolt, they provide resources to pollinators that in turn facilitates the possibility of saving your own seeds for subsequent plantings. Indeterminate types of tomatoes will grow to 6-12 feet high and can be trained to grow over an arch. These tomatoes come in a plethora of sizes and colors to provide season-long aesthetics and flowers for the bees.

Rabbiteye blueberries (Vaccinium virgatum) are a native shrub originating in the southeastern U.S. and thus well-adapted to our soil and moisture conditions in southern Louisiana. Plants thrive in the same soil conditions suitable for azaleas and rhododendrons and can be trained as hedges in home gardens. They are also the host plant for the southeastern blueberry bee (Habropoda laboriosa), which is the most efficient pollinator of this crop. They develop as larvae in underground nests and are active as adults only for a few weeks every year when blueberries are flowering.

Squashes and gourds (Curcubita sp.), in addition to being excellent sources of vitamins A and C, are the host plants for a number of native squash bees. Originally specializing on buffalo gourd, as agriculture spread in North America, so did the ranges of these native bees. Peponapis pruinosa, among others, are specialists on squash flowers and the most effective pollinators of crops such as zucchini, pumpkins and squash (like butternut, buttercup and spaghetti) because their biology is closely linked to that of their host plants. Females provision their young only with squash pollen, so observe flowers first thing in the morning when flowers are most fertile for these native visitors. Females nest in the ground near host plants, so leave some bare soil nearby to encourage a healthy population, and hearty supply of squash!

Plants belonging to the nightshade (Solanaceae) family include tomatoes, tomatillos, peppers, eggplants and potatoes. These plants all require a specific type of pollination, called “buzz pollination,” to release their pollen. This technique can be carried out only by bumble bees and certain other native bee species, in which they rapidly vibrate their flight muscles when they visit the flower. Although varieties of tomato and pepper do not necessarily need to be pollinated to set fruit, a higher quality harvest is achieved by a healthy pollinator presence.

Substituting fruit trees for other common shade trees is a great option for southern Louisiana residents. Honey bees and numerous other native bees visit blossoming citrus trees for the abundant nectar and pollen. Oranges are particularly good nectar producers in the spring, but lemons and limes will bloom continuously through the year. Grapefruit is also a good nectar producer, but few are grown in Louisiana. Although they can be pests for citrus farmers, the Giant Swallowtail (Heraclides cresphontes) uses citrus as a host plant, with the larvae resembling bird droppings to deter predators! Pears adapted to our climate and persimmons are other low-maintenance options.

Figs (Ficus carica) have a unique pollination syndrome in that their flowers are not visible, but open inside of a hollow stem called the scion. Instead of attracting bees, they rely on a tiny, seemingly insignificant wasp (Blastophaga psenes) for the “fruit” to develop. These wasps do not sting and would likely go unnoticed in your garden if not for all the figs on your tree!

Before purchasing or planting any trees, be sure you locate them in a well-draining part of your yard that is not susceptible to frost, since fruit trees can be damaged by freezing temperatures.

Herb gardens are a great way to incorporate lots of floral diversity in relatively small areas, especially since most will grow well in pots. Herb plants have a wide diversity of flower types, which, in turn, will attract numerous different types of pollinators to your garden, particularly butterflies. Caterpillars like the Black Swallowtail (Papilio polyxenes) can use caraway, dill, fennel and parsley as host plants, though adults feed on nectar from many herbs, including chives, Echinacea, marjoram and mint. Bees benefit from flowering basil, lavender, hyssop, borage, rosemary and thyme, among others.

Although it is a common practice to pinch off flowers of herbs to encourage more leaf growth, allowing some to bolt will greatly increase the diversity of beneficial insects in your yard.

Prickly pear cactus, Opuntia engelmannii, has a native range that extends east into Louisiana and is a common landscaping plant. Native Americans across the southern part of the country utilized the younger pads (or nopalitos) and fruits as food. While a less common practice among home gardeners today, the flowers of this cactus are an important resource for bees of Diadasia and Melissodes present in Louisiana and many other pollen generalists. Please note: the spines of prickly pear cactus can cause severe inflammation of the mouth and throat. If you plan on growing this plant for food, research the best ways to safely remove spines before consuming, or plant a spineless cultivar.

 

Constructing Backyard Bee Hotels

North America is home to approximately 4,000 species of native bees, of which 30% are wood nesters that build their nests inside of hollow tunnels. These tunnels may be pithy stems, beetle holes or burrows excavated by the bees themselves (carpenter bees). Unlike honey bees, which work together to construct their hives of comb made from beeswax, the females of solitary native bees build and provision their nests by themselves. Typically, these solitary bees use materials gathered from the environment, such as pieces of leaves or flower petals, mud, pebbles and tree resins. Because many of our native bees are able to forage only within a couple hundred meters of their nests, providing nesting structures in the vicinity of your pollinator garden will encourage nesting and pollination year after year!

Bee hotels are an easy way to provide artificial nesting sites to observe the behaviors of our gentle native bees. Unlike honey bees, native bees are less defensive of their nests and thus allow you to closely observe their foraging trips, bringing pollen back for their young. Wooden nest blocks can be constructed from preservative-free pieces of 4×4 or 4×6 lumber, or with pieces of firewood or fallen logs. These simulate the beetle holes bees encounter in the wild. Holes should be drilled into the block 3-6 inches deep, 3/4 inches apart and between 3/32 inch (2.5 mm) and 3/8inch (10 mm) in diameter. Alternatively, stem bundles of bamboo reeds of various sizes that are cut at the nodes, such that one end is closed, also can be provided for nesting. Hang or mount nests securely in protected locations that face east with afternoon shade. Charring or painting the front has been shown to attract bees more, but otherwise the structures can be painted any color or left natural.

Depth is important when drilling holes, as female bees can control the sex of their offspring, and will lay male eggs closer to the entrance. Deeper holes encourage them to produce more female offspring, which will in turn pollinate your garden.

 

Females of the leaf cutter bees (Megachilidae) can be seen cutting perfect circles of leaves, which they use to line their nests. Unlike honey bees, they carry pollen under their abdomens.

Even if you never observe the females, you will know when mason bees have been using your hotels, as they plug the full tunnels with mud to protect their young. Once mature, the new adults chew their way out.

When setting aside pollinator habitat, keep in mind that 70% of native bees are ground nesting; leaving mulch-free areas of soil in your garden will give these important pollinators a place to live in your yard as well.

Extravagant 5-star bee hotels also can be used as a focal structure in your garden. Growing turf or other plants as a green roof will help to keep the interior cool. These can incorporate broken and upcycled garden supplies for nesting.

 

LSU Ag Center Series/  Download Brochure on Pollinator Gardening Here
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ownload Brochure on Conserving Pollinators with Edible Landscaping Here
Download Brochure on Constructing Backyard Bee Hotels Here