WISDOM FROM THE WILD CHILD GARDEN: MARCH 2023: POLLINATOR GARDENING: Part I
WHY A POLLINATOR GARDEN? Beneficial pollinators maintain balanced ecosystems and the health of our food supply through pollination. Native insects play a crucial role in pollinating and fertilizing up to 75 percent of plant species on earth, and up to a third of our staple food crops rely upon insects alone to disperse their pollen and fertilize their fruits.
WHAT IS A POLLINATOR? Pollinators are a diverse group of species which include birds, bees, butterflies, bats, moths, flies, wasps, and beetles. They are critically important to life, and are responsible for bringing us one out of every three bites of food. They also sustain our ecosystems and produce our natural resources by helping plants reproduce.
Pollinators travel from plant to plant carrying pollen on their bodies in a vital interaction that allows the transfer of genetic material critical to the reproductive system of most flowering plants. These plants bring us fruits, vegetables, and nuts, provide half of the world’s oils, fibers, and raw materials, prevent soil erosion, and increase carbon sequestration.
PLANNING THE POLLINATOR GARDEN:
• Organic Gardening: pollinators will not visit the garden if there are poisons present. Choose natural pest control methods such as homemade sprays with cayenne, garlic, horsetail, or stinging nettles, or horticultural soap.
• Native Plants: share a long evolutionary history with their pollinators, so including a wide variety of natives will make the garden a favorite destination for pollinators. Choose carefully to match the site conditions. Natives will flourish without the addition of fertilizers and pesticides.
• Pollinator Plants: choose nectar and pollen-rich flowers with a range of shapes, sizes, and colors. Diversity is the key to a good pollinator garden. Because each pollinator has its own techniques for sourcing nectar and pollen, flowers should be as varied as the pollinators that visit them. Generalist pollinators can visit a wide variety of flowers, and specialist pollinators need a very different diet and may only be able to feed from one or two kinds of plants. Strive to provide plants for both types of pollinators. Choose plants with large, compound inflorescences of flowers, such as Joe Pye, goldenrod, and milkweed, to attract a diversity of insects and pollinators.
• Avoid Modern Hybrids: many garden plants have been manipulated for larger blooms and a show of color and may have lost their ability to produce nectar and pollen. In the breeding process, some flowers may become so complex that pollinators can't locate the nectar. When buying annuals, purchase older heirloom varieties known to have nectar and pollen.
• Succession Bloom: have several different plants in bloom from early spring through late fall. Some pollinators emerge in early spring, while others don't appear until mid-summer, but they all need pollen and nectar while they are active and rearing their young. To maximize the effectiveness of the pollinator habitat, have a variety of plants in bloom throughout the season. Overlapping bloom times will ensure there is always something in the garden to provide nutrition for pollinators.
• Plant in Drifts: pollinators are more likely to find plants in gardens that provide larger drifts of color. Choose at least three or more of one kind, more if there is room, and plant them near one another.
• Avoid Landscape Fabric & Mulch: instead, place plants closer together. Plants of varying heights planted close together will form a weed barrier far superior to a bed of mulch. The bonus is that there will be room for many more blooms for pollinators.
• Save Perennial Garden Cleanup for Spring: pollinators overwinter in different life stages including eggs, larvae, pupae, and adults. Some overwinter in hollow stems, while others attach to plants or overwinter in the leaf litter. To protect overwintering pollinators, don't cut down perennial gardens until spring, and keep beds of leaves intact through the winter.
BATS: take the night shift and play a major role in pollinating crops and spreading seeds. They feed on flowers, including those of valuable commercial crops, like figs, dates, mangoes and peaches, which have flowers that only open at night. These mammal pollinators are finicky eaters with a specific palate. Dining on plant pollen and drinking sweet nectar is a delicacy at its batty-best. They tend to enjoy a flower that’s mild in scent and not bright in color, and white or pale crop flowers attract the night pollinators that feed on them.
Bat species found in Tennessee include the big brown bat, little brown bat, Eastern red bat, Eastern small-footed bat, evening bat, hoary bat, Indiana bat, Northern long-eared bat, silver-haired bat, Townsend’s big-eared bat, and the tri-colored bat.
BEES: make excellent pollinators because most of their life is spent collecting pollen, a source of protein that they feed to their developing offspring. When a bee lands on a flower, the hairs all over the bees' body attract pollen grains through electrostatic forces. Stiff hairs on their legs enable them to groom the pollen into specialized brushes or pockets on their legs or body, and then carry it back to their nest.
Individual bees tend to focus on one kind of flower at a time, which means it is more likely that pollen from one flower will be transferred to another flower of the same species by a particular bee. Many plants require this kind of pollen distribution, known as cross-pollination, in order to produce viable seeds. The business of collecting pollen requires a lot of energy, and so many flowers attract and also reward bees with nectar, a mixture of water and sugars produced by plants.
Bee species found in Tennessee include the bumblebee, European honeybee, carpenter bee, mason bee, long-horned bee, sweat bee, squash bee, digger bee, polyester bee, masked bee, cuckoo bee, leaf-cutter bee, and miner bee.
BEETLES: were among the first insects to visit flowers and they remain essential pollinators today. Fossil records show that beetles were abundant during the Mesozoic period and were flower visitors of the earliest angiosperms. Many present-day beetle pollination associations like that of magnolia, a primitive woody angiosperm, and spicebush have ancient evolutionary origins.
Beetles will eat their way through petals and other floral parts. They even defecate within flowers, earning them the nickname “mess and soil” pollinators. The flowers visited by beetles are typically bowl-shaped with sexual organs exposed, white, to dull white or green, strongly fruity, open during the day, moderate nectar producers, have large solitary flowers such as magnolias and pond lilies, or have clusters of small flowers like goldenrod and spirea. Beetles rely on their sense of smell for feeding and finding a place to lay their eggs. Scents associated with beetle pollination are often spicy, such as the crab apple, sweet, such as the wintersweet shrub, or fermented such as the sweet shrub.
Beetle species found in Tennessee include the blister beetle, the red-necked false blister beetle, leather wing, the locust borer, and the longhorn beetle.
BIRDS: are very important pollinators of wildflowers throughout the world. There are 2,000 bird species globally that feed on the nectar, the insects, and the spiders associated with nectar bearing flowers. In the United States, hummingbirds are key in wildflower pollination.
The flowers that are visited by birds and hummingbirds are typically tubular and have petals that are recurved to be out of the way, have tubes, funnels, cups, and strong supports for perching, are brightly colored in hues of red, yellow, or orange, are odorless since birds have a poor sense of smell, are open during the day, are prolific nectar producers with nectar deeply hidden, and are modest pollen producers that are designed to dust the bird’s head and back with pollen as the bird forages for nectar.
Hummingbirds have very good eyes and are extremely attracted to red. They thrust their long slender bills deep into the flowers for nectar, withdrawing faces dusted in pollen. Although a hummingbird weighs between two and eight grams (a penny weighs 2.5 grams), they eat frequently in order to power hearts that pump 1,200 times per minute and wings that beat seventy times each second. To survive, they must eat several times their weight in nectar every day! For protein, they supplement their sugary diet with small insects. The ruby-throated hummingbird is the most common species bird found in Tennessee.
FLIES & WASPS: are less known as pollinators but do a yeoman’s share of the work. After bees, flies are the most important pollinators, and hundreds of fly species visit crops. Hoverflies and blowflies visit flowers to drink nectar, which fuels energetic activities like flying, and eat pollen to get the nutrients needed for sexual maturation. Like bees, many of these flies are hairy and trap pollen on the head and thorax as they feed. Larger flies can collect and carry hundreds to thousands of pollen grains as they fly from flower to flower.
Unlike bees, which must forage close to their hive or nest, flies don’t have to provide for their young and can roam more widely. Flies are attracted to things that smell bad like garbage and dead animals, so fly-pollinated flowers produce a bad odor like rotting meat. The flowers are plain in color like meat, or darker shades like brown and purple. Fly-pollinated flowers are shaped like a funnel and sometimes act as a trap to catch the insect. Many fly-pollinated flowers do not produce nectar. Flies enter the flower because they are attracted to the smell, picking up pollen along the way and once they realize there is nothing to eat inside, they move on.
Wasps are helpful pollinators, and since the adults live mostly on sugar, they visit flowers to collect nectar, moving pollen around on the way. Wasps have fine and invisible hair on their bodies to which pollen can cling. When it comes to pollinating, wasps are “generalists” that will pollinate just about any flower, and some have a specific purpose such as pollinating figs. A tiny fig wasp finds a fig with flowers, and shimmies through a small opening, often tearing off her wings and antennae in the process. Now, flightless and stuck inside, she lays her eggs and then dies. When the eggs hatch, they mate with other wasps born in the same fig. After mating, the males dig a path out for the females so they can find new figs. The wingless males then die inside the fig.
MOTHS: after dark, moths take over the night shift for pollination. Nocturnal flowers with pale or white flowers that are heavy with fragrance and copious dilute nectar attract these pollinators. Not all moth pollinators are nocturnal, and some moths are also active by day. Some moths hover above the flowers they visit while others land.
Hawkmoths are impressive flyers and some have tongues longer than their bodies. These giant moths fly upwind, tracking the airborne fragrance trail to a clump of flowers. Their caterpillars, tobacco and tomato hornworms, are well known to gardeners as voracious feeders. If you want to see their colorful adults, sequester these offspring on a few plants in the corner of your garden.
The flowers that are visited by moths are typically clustered, provide landing platforms, are white or dull colors, open late afternoon or night, and are ample nectar producers, with nectar deeply hidden, such as morning glory, tobacco, yucca, and gardenia.
Moth species found in Tennessee include the beggar moth, the clearwing moth, the hummingbird clearwing moth, the grapevine borer, the smoky moth, and the unicorn prominent moth.
BUTTERFLIES: are very active during the day and visit a variety of wildflowers. Butterflies are less efficient than bees at moving pollen between plants because they are highly perched on their long thin legs, do not pick up much pollen on their bodies, and lack specialized structures for collecting it. Butterflies probe for nectar, their flight fuel, and typically favor the flat, clustered flowers that provide a landing pad and abundant rewards.
Butterflies have good vision but a weak sense of smell. Butterflies typically visit flowers that are clustered and provide landing platforms, are brightly colored, are open during the day, are ample nectar producers, with nectar deeply hidden and nectar guides present, or have clusters of small flowers like goldenrod and spirea. Many butterflies produce scents that attract the opposite sex, and these scents often smell like the flowers that they are attracted to and visit. The scent of these butterfly-pollinated flowers might have evolved as an adaptation that made use of the existing attractiveness of these scents.
CATERPILLARS: it is important to provide flowers that attract butterflies, but there’s another important element that is often overlooked: the baby nursery. Without the specific plant species needed, called larval host plants, butterflies have nowhere to lay their eggs. The pollinator garden should provide plants that support complete metamorphosis, and offering food and drink that encourages full-fledged butterflies will attract these beneficial pollinators. In order for them to stay and increase their populations, food must be provided for their caterpillars.
Once mated, the female butterfly has to find a place to lay her fertilized eggs, and she seeks out the unique and necessary food plants that her species has co-evolved with over countless generations to ensure that her young will be able to start feeding immediately after they hatch, thus aiding their survival. She looks for the right leaf shape and shade of green, then ventures closer. Butterflies taste with their feet by drumming their feet on the leaf to make sure it’s the right plant. Then she lays one, several, or lots of eggs under the leaf, on the leaf, on the flower or stalk, or at the leaf axils, depending upon her species.
Generalist or penultimate species such as painted lady and mourning cloak utilize a wide variety of nectar and larval host plants. Specialist or obligate species such as monarchs can nectar on a wide variety of plants, but the caterpillar can only eat milkweed.
CHOOSING LARVAL HOST PLANTS:
• Make a list of butterflies commonly seen in the garden.
• Research their larval host plants.
• Dill, hollyhock, and milkweed support a wide variety of species.
• Dill and parsley attract the black swallowtail.
• Legumes attract sulphurs.
• Grasses attract skippers.
• Trees attract admirals.
• Milkweed attracts monarchs.