Supporting Biodiversity in the Garden

For more information about welcoming bees to your garden, visit the Delaware Department of Agriculture’s Farming for Native Pollinators page (http://dda.delaware.gov/plantind/pollinator.shtml ) and the UD Cooperative Extension Beekeeping page (http://ag.udel.edu/extension/horticulture/beekeeping.htm ).  

Lepidoptera 

(Butterflies, Skippers, Moths & Their Caterpillars) Pollination is an important role played by butterflies, skippers and moths, but perhaps their more essential role is to serve as a food source for birds, bats, small mammals, and other predators both in their larval (caterpillar) and adult stages. Humans find special interest in the beautiful colors and delicate form of adult Lepidoptera—the collective name for butterflies, skippers and moths. 

To encourage adult Lepidoptera to visit your garden, you must provide for their young: caterpillars. While adults are more general about the flowers they seek nectar from, most caterpillar species require specific plants for survival. Providing their host plants in your garden—as well as a variety of nectar plants—is the best recipe for filling your yard with these fascinating flutterers. Many gardeners balk at the idea of providing fodder for leaf munchers, but attracting caterpillars also means attracting their predators, which will prevent the leaf munchers from causing noticeable damage.

Butterflies and skippers require nectar meals to give them the energy to mate and reproduce. They can drink from a variety of flowers; their good vision leads them to red and orange blooms in particular. In general they prefer clusters of flowers for one-stop sipping and daisy shapes whose petals provide a perch. 

Butterfly and skipper plants should be located in the sun because the insects require warmth to generate energy for flight. Flat stones placed in the sun provide a morning resting place for drying dewy wings. Mud puddles also benefit certain species of butterflies that use them to obtain mineral salts. 

Unlike butterflies, moths hover when they feed, using their long mouthparts to extract nectar from long, tubular flowers. In fact, due to this behavior, some moths are easily mistaken for hummingbirds—especially the hummingbird clearwing moth with its fast-beating wings. Hummingbird clearwing moth Photo: Doug Tallamy 

Moths fly in the evening or nighttime hours, and many drink nectar from night-blooming, pale or white flowers that are easiest to see. Due to a keen sense of smell, many moths are drawn to flowers that exude a strong, sweet aroma. However, some moths lack mouthparts and do not feed at all before mating. This includes the giant silkworm moths, a family that contains many of the large colorful moths considered quite attractive by humans. Providing food for their caterpillars is the only way to entice them to the garden.  

Butterflies, moths, and skippers all require shelter and protection from inclement weather, which can be achieved in your garden by dense shrub plantings, old logs, or piles of brush. Food plants for all stages of Lepidoptera should also be protected from wind by a hedgerow, fence, or wall.  

For a list of the "20 Most Valuable Woody and Perennial Native Plant Genera in Terms of Supporting Biodiversity in the Mid-Atlantic Region" by Doug Tallamy, visit the UD Botanic Gardens’ Native Garden page at http://ag.udel.edu/udbg/gardens/native.html

Nectar-feeding Birds 

Nectar serves as a food source for both hummingbirds and orioles, birds that play important roles as pollinators. Hummingbirds use their long, specialized beaks to extract nectar from long, tubular blooms, flocking to red flowers as well as various shades of dark orange and dark pink. Orioles drink nectar from blooming tulip trees (Liriodendron tulipifera) to supplement their diet of fruits, insects, and spiders.  

Hummingbirds appreciate shrubs with small branches to accommodate their small feet and plants with large leaves to provide protection from inclement weather. They bathe and drink from shallow pools of water and even in water droplets caught on the surface of curved leaves. In times when water is scarce on the landscape, a commercial mister can be used to provide water for hummingbirds.  

Though tulip trees provide a sweet snack for orioles, your garden should also include berry-producing plants and support a variety of insects and spiders to make it a desirable environment for these part-time nectar drinkers. Orioles weave basket-like, gourd-shaped nests from plant fibers, which they hang from the ends of tree branches to keep out of predators’ reach. You can help them by setting out natural fibers like jute, raffia, yarn, corn husks, and straw, cut to lengths of no more than 6 inches. Providing trees with wide-reaching branches increases the chance of them nesting on your property. 

Insects  

Insects have traditionally been excluded from the garden rather than welcomed, but wildlife gardeners recognize their enormous potential for supporting biodiversity. Spiders, birds, mammals, amphibians, reptiles and even other insects depend on them for food, and many plants require their pollination services.  

Beetles especially serve as a fantastic testament to the wonders of biodiversity: More than half of all animal species are insects, and more than half of those are beetles! Though, like caterpillars, the majority of beetles eat leaves, gardeners should not hesitate to welcome them into their garden. Research has shown that plant damage from leaf munchers will be minimal to the human eye in balanced backyard ecosystems that provide habitat for insects and insect predators while avoiding the use of herbicides and pesticides.  

Many beetles and other insects eat pollen and nectar from plants with dense clusters of flowers during certain stages of their lifecycle. Flowers in the aster family (daisy shaped blooms) are some of the best types of flowers for attracting beneficial insects in general. Mini-wasps are parasitoids that attack many pest insects, like drinking from tiny flowers with easy-to-reach nectar. This includes members of the carrot family whose upside-down umbrella-shaped blooms provide a flat platform composed of hundreds of miniature flowers.  

A low-growing ground cover or a layer of leaf litter in your garden provides needed habitat for beneficial insects as well as many of their predators. Shallow bird baths or stone-lined saucers are great ways to provide water for beneficial insects as well as other wildlife. 

For more information about specific beneficial insects, especially in their use as biological pest controls, consult the UD Cooperative Extension facts sheets available at http://ag.udel.edu/extension/horticulture/insects.htm

Songbirds 

The twittering and fluttering of birds liven the landscape during all seasons, both for humans as well as their prey and predators. Insects comprise the vast majority of the diet for most backyard songbirds, especially when they are breeding. Providing a diverse cover of plants— especially natives—will do dual duty in attracting not only insects but also the birds that prey on them. Leave a layer of leaf mulch on the ground to aid birds in foraging for the insects, spiders and worms that hide there. 

Many birds also enjoy plants replete with fruits, nuts and seeds. For the greatest impact, use a combination of summer- and fall-fruiting plants, as well as plants that hold onto fruits into winter and spring until the cycle of freezing and thawing renders them ripe.

To provide optimal bird habitat in your landscape, include the various levels of vegetation found in their natural environment. Ground-dwelling birds appreciate shrubs, grasses and perennials for shelter; understory trees and canopy trees serve birds that nest in the middle and top layers of the forest. For many species of birds, evergreens provide important protection during storms and, for non-migratory species, throughout the winter months. Homemade or commercial birdhouses provide additional lodging options for birds that dwell in tree cavities carved out by either a previous inhabitant or natural weathering processes. Finally, the ubiquitous bird bath speaks to another bird need—a shallow water source for drinking and bathing. Shallow puddles generally suffice, as well as homemade or commercially-produced bird baths, with the latter providing the bonus of an attractive landscape feature.

For information about specific bird-attracting plants (including their hardiness zone), consult North Carolina State University’s Attracting Birds website at http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/birds/bird_index.html