Planting Perfume for Pollinators
Help plants native to your region and the creatures that pollinate them by creating a garden filled with fragrant flowers
ANYONE WHO HAS APPLIED a few strategic spritzes of perfume or a slather of aftershave before a big date knows that scent is one of the most potent tools of sexual seduction. The technique was invented at least 100 million years ago by plants.
Plants perfume their blooms to attract the insects and other animals they need to pollinate their flowers. Floral fragrance is a kind of olfactory come-on that proclaims to a potential flower fertilizer, “Come hither, honey, ’cause there’s scrumptious pollen and sweet nectar hidden inside these pretty petals.” In addition to a full belly, the pollinator leaves the flower with pollen attached to its body in a bundle or dusted on its fur. When it lands on another blossom while looking for its next meal, cross-pollination can occur. Without their pollinators, many plant species cannot set seed and reproduce.
At a time when habitat loss, indiscriminate use of pesticides, and a host of other problems are disrupting this age-old reproductive duet, home gardeners can lend plants and their pollinators a helping hand by creating backyard habitats full of fragrant flowers. Peonies, gardenias and other exotic species may be the most familiar scented plants, but a variety of beautiful native trees, shrubs and wildflowers are fragrant, too. By cultivating them we not only help support the bees and other native pollinators with which they’ve coevolved, but also get to enjoy the plants’ heady scents ourselves.
Every plant has its own signature scent, a complex mixture of so-called volatile organic compounds that easily turn to gases and waft through the air. Some 1,700 different compounds from 990 different plants have been identified in flower fragrances so far, according to Natalia Dudareva, a Purdue University biologist whose specialty is floral scents.
Pollinators are picky about these flower odors. You could say that it’s all in the proboscis of the beholder (or antennae, the olfactory organs of bees, beetles and moths). For example, native bees prefer blooms with a sweet fragrance, such as California wild lilacs and the white or pink flower spikes of the summersweet shrub, which perfumes eastern U.S. woodlands in midsummer.
Moths, which are mostly nocturnal, are attracted to wildflowers like evening primroses, which advertise their presence under the cloak of darkness with powerful sweet perfumes. One of the most cunning practitioners of floral seduction, the sacred datura of the Southwest, attracts its hawk moth pollinators to its huge white, trumpet-shaped flowers with a sweet siren scent, and to increase the chances that the insects get dusted up with pollen, keeps them inside the blossom by producing a narcotic nectar.
Bats, also night flyers with good noses, favor blooms with musty aromas. Most bats in the United States are insectivorous, but three flower-eating species pollinate dozens of agaves and giant cacti in the Southwest deserts, including the organ pipe cactus and cardón.
If they think about beetles at all, most gardeners see them as pests that chew holes through their prized flowers. But these handsome insects, often with bright or metallic-colored wing cases that are extravagantly striped or spotted, are important pollinators. In fact, beetles were the pinnacle of insect evolution during the early Cretaceous period when flowering plants began to evolve. Although they’re virtually colorblind, these primeval pollinators have a great sense of smell and follow their noses to primitive flowers with fruity and spicy scents, such as magnolias. Other favorites include California spicebush and its eastern cousin, Carolina allspice, which has odd, dark reddish-brown flowers with layers of curved, straplike petals and a fruity fragrance.
Most people don’t think of flies as pollinators either, but they play a critical role in the fertilization of some flowers. Flies fancy blossoms that emit the essence of carrion or dung and look like lumps of rotting flesh. Among their preferred wildflowers are red trilliums, known as “stinking benjamins” by early naturalists, and aroids such as jack-in-the-pulpit and skunk cabbage, which has tiny flowers massed together along a fleshy pole partially surrounded by a leaf that smells like stinking fish.
Birds and most butterflies don’t have good olfactory senses, and the plants they pollinate don’t waste energy emitting fragrances. Instead, they strut their stuff with colorful and distinctive-shaped flowers.
How You Can Help
The following rules of thumb can help you create a garden of fragrant native plants that is as enticing as possible for people and pollinators alike:
• To provide pollinators with the plants to which they are best adapted and avoid introducing invasive species, select flowers native to your region. The fragrant water-lily, for example, is a fine choice for water gardens or even small tubs in its native East but can be invasive in the West.
• Invite a variety of pollinators into your garden by offering a diverse mix of fragrant flowers, both day and night bloomers. For recommendations, consult the Pollinator Partnership, a coalition of conservation groups, the Lady Bird Johnson Wildflower Center or the Xerces Society.
• Plant favored species in drifts of at least three to five to make them worthwhile for pollinators to visit.
• Design your garden so that there is a continuous succession of plants in bloom to provide nonstop food sources for hungry pollinators.
• Plant in an enclosed space, such as inside a courtyard or a hedge of native roses, which can prevent the fragrance from being whisked away by the wind. The reflected heat from a wall or patio can intensify floral fragrance.
• Don’t use pesticides, even nonchemical ones such as Bt, which can decimate pollinator populations.
New York journalist Janet Marinelli writes frequently about native plants for this magazine.