Flowering plants emerged 100 million years ago, and during the Cenozoic era some 40 million years later, ascended into the world’s vegetation. Much of their co-evolution was mutualistic: whole complexes of species came to seal obligatory partnerships with their insect counterparts.
Edward Wilson, The Forgotten Pollinators
Isn’t it time, after sixty million years, that we begin to establish an appropriate relationship with insects and plants, a long overdue tête-a-tête in our gardens? Can’t we apply the same sort of wisdom and understanding that we now reserve for our feathered garden visitors?
A habitat garden provides a setting for wild creatures to exist happily with people. It includes plants selected to attract and feed beneficial insects, butterflies (both caterpillars and adults), pollinating insects, and birds. These creatures need flowering and fruiting plants to sustain them—some along their migratory routes, and some where they live seasonally or year round. Increasing development, human population growth, and toxic sprays all play a role in decreasing natural habitat for many of these creatures; the provision of plants for them to eat can help them both on their journeys and in your neighborhood. In return they will reward you by preying on plant-eating insects, pollinating the flowers in your garden, and entertaining you by their beauty and amusing habits. A healthy garden has hundreds of different kinds of wild creatures living in it or visiting it, each with its own unique story to tell. With observation and a little research, much can be learned about this ecosystem in miniature, which is too often unnoticed and unappreciated in our gardens.
The Fetzer Habitat Borders
I was inspired to create a habitat garden after observing a brilliant border of summer annuals. Hummingbirds and butterflies darted and swooped amongst the vibrant colors like whirling airborne flowers; the effect was dynamic. In the five-acre winery garden that I design and maintain (Fetzer Vineyards in Hopland, California), hummingbirds and butterflies never fail to excite our guests, invariably stopping tour groups in their tracks. One of the purposes of the winery’s garden is to encourage a broader understanding of the value of organic gardening and farming practices. Incorporating plants that attract beneficial insects would show visitors how a balance of insect life in a garden or farm crop can alleviate the need for the many chemicals applied to conventional farms and gardens. I added plenty of milkweeds for the monarch butterfly caterpillars to demonstrate the importance of preserving habitat for some of our migratory species. I also added flowers that provide food for birds such as finches, whose antics are so amusing as they harvest seed from the flowers. Pollinating insects, many native to the area, have appeared in great numbers, attracted by the same flowers that appeal to butterflies and beneficial insects. This area has become the favorite part of the garden for our guests (human and otherwise).
We chose a site that was formerly a vegetable production area. Approximately 150 feet by 50 feet in size, it gets full sun and is centrally located within the garden for maximum visibility. We created two, twenty-foot-wide, undulating borders backed by espaliered apples and separated by a broad central path; benches provide places for guests to sit and enjoy the lively and colorful scene. We amended the heavy clay soil with compost made from grape pomace and garden trimmings. Irrigation is provided by drip tape spaced two feet apart and running the length of the borders; this provides a slow but thorough watering, controlled by a timer. A birdbath and shallow saucers on the ground provide water for wildlife (from birds to toads). Small trees, shrubs, perennials, and annuals combine in the garden to create a dense, multi-tiered planting, which provides many places for birds to hide, secure enough to linger in the garden. Nearby tall trees provide nesting places for the birds.
From our experience in developing the habitat borders have come a number of basic ideas to consider in developing a habitat garden. Many insects and birds prefer particular kinds of plants. The trick to a successful habitat border is to combine a variety of plants to draw a broad range of wildlife to the garden. Focus on plants that grow well in your climate and attract local insects or birds. Native plants are often the best to use since the creatures you will be attracting are generally natives, but don’t restrict yourself. Combine plants that flower early in the season, with mid- and late-season bloomers to provide nectar and pollen sources over a long season. Concentrate on plants that flower over a long period of time. Stagger plantings of short lived, seed-bearing plants such as sunflowers, or select those that flower over a long season. Include late-season, fruiting plants to keep birds in your yard. As in any good garden, group plants according to their preferences for sunlight, soils, and water. Forget about using pesticides or herbicides of any kind. Select a full range of plant types—trees, shrubs, herbaceous perennials, and annuals. Mix heights, textures, densities, and species together for an informal effect. Aim for exuberance, and make every inch of your garden spill over with plants.
When planning for butterflies, consider both the larvae (caterpillars) and the adults, as both need food. Caterpillar food plants are called larval plants; each kind of butterfly generally favors a specific plant family for its larvae to feed on. Some butterflies are widely distributed throughout the country, whereas others live in a limited area. Find out which species live in your area to learn what types of larval plants to include. A common butterfly in California and the Northwest is the anise swallowtail. Its larvae like dill, fennel, and other members of the carrot family. Common fennel (Foeniculum vulgare) is an easy perennial to grow, and does double duty with flowers that appeal to beneficial insects as well. Larvae of the more earth-toned buckeye butterfly prefer plantains (Plantago spp.) and plants in the snapdragon family (Scrophulariaceae). Monarch caterpillars are more limited in their food, feeding exclusively on milkweeds; the poisonous alkaloids in the foliage make the caterpillars and their adult forms poisonous.
Butterfly caterpillars are fun to identify and observe, particularly as they mature and metamorphose into chrysalises and finally into adult butterflies. Some chrysalises are jewel-like; those of the monarchs have an iridescent gold band delicately laced on a brilliant, lime green case. Other species produce more modest chrysalises, but all are fascinating to watch as the adults burst forth, dry their wings, and take flight. Adult butterflies feed on nectar, and prefer flowers that provide a broad and easily accessible landing pad. Verbenas (Verbena), thistles (Cirsium, Carduus, and others), butterfly bushes (Buddleja), California lilac (Ceanothus), milkweeds (Asclepias), Joe Pye weed (Eupatorium purpureum), California buckwheats (Eriogonum), Lantana, Mexican sunflower (Tithonia rotundifolia), clovers (Trifolium), and most daisies (Cosmos, Coreopsis, Aster, Dahlia, and others), are all plants that adult butterflies favor, and are easily grown in most areas.
Insects beneficial to farmers and gardeners are either predators or parasites on pest insects. They impale, kidnap, paralyze, decapitate, or suck dry insects that feed on plants of farm and garden; a magnifying glass in the garden reveals a world that makes TV horror shows pale by comparison. Using insects to control other insects is not a new concept. This type of biological control dates back to the fourth century AD, when ants were manipulated to control citrus pests in China.
Some of these beneficial insects are general predators and will eat eggs, larvae, and adults of almost any insect they can overpower. Among the general predators are lace wing and ladybug larvae (adults feed on aphids), various beetles, big-eyed bugs, minute pirate bugs, assassin bugs, spiders, predatory thrips and mites, and predatory flies like the syrphid fly larvae. Parasitic insects are usually specific in their food preferences, not only attacking a specific insect, but often at a specific stage in the insect’s life. Common parasitic insects are the minute wasps, such the trichogramma, aphidius, and others, that do not sting people (some are only 1/250 of an inch long) but lay their eggs on other insects; their larvae feed on these host insects, ultimately killing them. Among the insects parasitized are aphids, caterpillars of all kinds, scales, whiteflies, mealybugs, psyllids, thrips, leafminers, flies, Mexican beetles, and various grubs. A well-planted habitat garden will have a changing cast of these do-gooders throughout the gardening year.
Plants in the carrot family attract many of these beneficial insects; their nectar, on which the adults feed, is found in short tubes that are easy for these tiny insects to access. California lilac, coyote bush (Baccharis), yarrow (Achillea), mints (Mentha), buckwheats, Eupatorium, sweet alyssum (Lobularia), madwort (Alyssum), and milkweeds will also bring many of these creatures into your garden to do their good work. On warm afternoons, small clouds of beneficial insects swarm around such flowers enjoying the nectar and pollen. A selection of these plants in your habitat garden will provide you with a long season of bloom to capitalize on the widest array of beneficial insects.
Pollinating insects are also beneficial to a garden. Honeybee populations have been decimated by the parasitic varroa mite, a tracheal mite, and numerous diseases. Fortunately, a variety of native pollinators are ready to take their place with the right plants and habitats to attract them. These native pollinators range from bumblebees of every size—usually the first pollinators to appear in the spring—to small solitary bees that lay their eggs in individual holes alongside a ball of nutritious pollen (food for the larva). Because the solitary bees do not live communally, they do not defend their nest, and are not aggressive to humans. The same is true for solitary wasps. There are other ground-nesting bees such as the alkali bee (Nomia melanderi), a gregarious bee from the Great Basin, now raised commercially for alfalfa pollination. An estimated 4,000 to 5,000 species of ground-nesting bees occur naturally in the continental United States alone. Hole-nesting bees include orchard mason bee, an early spring riser, Osmia californica, a later riser, and Heriades carinata, a bee that likes hot weather. These bees can be purchased along with nesting blocks pre-drilled with holes of the appropriate size. Predatory wasps, as well as nectar-consuming wasps and butterflies, also serve as pollinators of flowers. The hover or syrphid fly, whose larvae are often predatory, is a pollinator as an adult. It mimics a bee in its appearance and is easy to identify by the “X” on its back.
Some bees are specific about the kinds of flowers they visit and have adapted special mouth parts and leg hairs or appendages to harvest pollen from their favorite flowers; other bees are more general feeders. It is interesting to note that butterflies are satisfied with nectar containing twenty to twenty-five percent sugar, which is dilute enough to be sucked up through their long proboscis; bees prefer nectar with sugar content at fifty percent or higher so they can take extra back to the hive to feed their young. This helps explain why bees and butterflies gravitate to different flowers for their food.
Of the many kinds of birds that will be attracted to a habitat garden, hummingbirds are among the most spectacular. A garden well stocked with hummingbird plants can resemble a combat zone, with territorial, warring birds zinging almost nonstop through the vegetation. Some species live permanently in areas where the winter is mild, whereas others are temporary or seasonal guests as they migrate north or south. Both native and introduced plants in a garden supply the nectar that hummingbirds need. A variety of plants will offer a long season of bloom. California fuchsias (Epilobium canum) are a favorite for their summer and fall flowers. Mimosas (Albizia julibrissin), grevillias (Grevillea), bottlebrushes (Callistemon and Melaleuca), manzanitas (Arctostaphylos), snowberry (Symphoricarpos), autumn sage (Salvia greggii), wild currant and gooseberries (Ribes), monkey flowers (Mimulus), beebalm (Monarda), lion’s tail (Leonotis leonuris), beard tongues (Penstemon), trumpet vines (Campsis and Distictis), Bougainvillea, Zinnia, and many others provide flowers attractive to hummingbirds. They prefer plants with red or orange tubular flowers that are rich in nectar, but will visit others if nectar is available. Nectar maintains their high metabolism; hummingbirds also eat tiny insects that provide them with protein and other nutrients, particularly when they are feeding their young. In addition to entertaining us with their color and antics, hummingbirds are effective pollinators of the plants they feed on.
Finches are handsome birds in the garden. They are generally seed-eaters, although some like insects and crops, particularly berries. They may not be effective for biological control, but are still amusing and natural visitors to the habitat garden. Their antics as they harvest sunflower or amaranth seeds are a delight to watch. Most sunflowers have a short season; the native sunflower (Helianthus gracilentus) has small, bright yellow flowers that the birds love, and it blooms all summer. Consider planting the seed-forming amaranths (Amaranthus) such as ‘Elephant Head’ or ‘Giant Burgundy’. Both have large, spectacular, crimson heads. Although ‘Elephant Head’ produces thousands of seed, neither of these varieties reseed much, but beware of varieties such as ‘Hopi Red Dye’ (Amaranthus cruentus), which do reseed readily and can become a serious problem in your garden (or your neighbors’).
Constant activity, beneficial to man, beast, and nature, flowers appealing to bird, man, and insect—such is a habitat garden. No one should be without one.
For Further Reading…
Buchmann, Stephen, and Gary Nabhan. The Forgotten Pollinators. Washington, DC: Island Press/Shearwater Books, 1996.
Flint, Mary Louise, and Steve H Dreistadt. Natural Enemies Handbook. Publication 3386. Berkeley: University of California Press, 1998.
Griffin, Brian. The Orchard Mason Bee. Bellingham, WA: Knox Cellars, 1993.
Stokes, Donald and Lillian. The Butterfly Book: An Easy Guide to Butterfly Gardening, Identification and Behavior. Boston: Little, Brown, 1991.
Udvardy, Miklos DF. The Audubon Society Field Guide to North American Birds. New York: Knopf, 1977.
The Xerces Society and The Smithsonian Institution. Butterfly Gardening. San Francisco: Sierra Club Books, 1998.