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Hummingbirds and Orchid Trees
Is
a butterfly shunned by his brood mates if he visits a non-native
plant? Do hummingbirds sleep alone if they sample an exotic nectar? |
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Recently I read an article in a prominent environmental journal about attracting hummingbirds to the home garden. The author advised that non-native plants are "bred not for nectar production but for showy flowers" and to "avoid using exotic flowering plants" in the garden. Thunderation! This fellow never visited our gardens. Every local birder knows that it is nearly impossible to attract ruby-throated hummingbirds to that exotic of exotics - the hummingbird feeder. The birds have so many alternatives here in South Florida that they do not feel compelled to indulge themselves on nutrient-deficient junk food. Simple observation indicates that hummingbirds show a preference, when they are given the choice, for a wide range of introduced flowering species. "Choice" is the key word. If animals are provided only local species they have no choice. Remember too, that many garden ornamentals are "native" to migratory birds even if they are not native to Florida. Tropical American species such as Hheliconia, abutilon (Flowering maples), malvaviscus (sleeping hibiscus), Hibiscus spp., jacaranda, pyrostegia (Flame vine), tabebuia (trumpet trees),chorisia (floss silk trees), orchids of many types and Mexican cupheas really turn hummers on. Hamelia is promoted as a native which attracts butterflies, but it should be pointed out that hamelia is also native to Central and South America. Try putting a West Indies Cestrum diurnum beside the hamelia and see which they prefer! Hummingbirds in particular are ethnic food gourmands. Their favorite dishes here in South Florida are totally foreign to their ranges: Asian Hong Kong Orchid trees (Bauhinia spp.) and Holmskioldia spp. (Mandarin hat plants), African species of Buddleja, Spathodea (African tulip) and Erythrina (coral trees). In California, hummers are much more aggressively opportunistic. There are great numbers of birds and the desert is a rather limited food resource. I have been buzzed by hummers intent on reaching African aloes in Balboa Park, and they have threatened to pierce my ears when I am photographing Australian anigozanthus (kangaroo paws) in the San Diego Zoo. The outdoor garden section of Home Depot there is a veritable war-zone of hummers quarreling over a smorgasbord of potted plants. There is a new symbiosis taking place between introduced plants and native animals, butterflies and most birds. As native habitats are decimated, non-native plant species sometimes are a suitable substitute and undoubtedly are keeping certain animal and other plant species from losing ground. The monarch butterflies migrating along the East Coast, in contrast to the western monarchs, are not dependent upon a localized Mexican habitat for their winter survival. In winter, they partake readily of the nectar of our winter flowering ornamentals like Calotropis, an African/Asian member of the milkweed family (Asclepiadaceae). They love Mexican Asclepias curassavica, which some consider an unworthy weed, but it is the natural food and host plant of monarchs in Mexico. Heliconius butterflies adore passionflowers of many kinds, and sulfur butterflies and daggerwings dine on cassias and sennas regardless of their passports. Being ignorant of the positive aspects of introduced plant species may be putting other more favored species at great risk - cutting off our noses so-to-speak. Swallow-tailed kites show a distinct preference for nesting in the lofty heights of Australian pines (Casuarina). They have returned for over a decade to the same nests in our neighborhood eschewing the native scrub pines even as temporary perches. These magnificent birds, threatened in some areas, are prospering here. Australian pines regrew quickly after the hurricane, a feat that native pines cannot accomplish. Fourteen juveniles gathered in the treetops before their migration south last year and the whole neighborhood turned out to watch their rapturous aerobatics. No doubt Australian pines disrupt the balance of nature within the Everglades and seaside communities. But they perform an important kite preservation service in suburban gardens where seed is unlikely to be transported to wild areas. What about environmental issues? Many, if not most, hybrid plants like the Hong Kong orchid tree are benign in the environment because they cannot reproduce themselves. Many species lack native pollinators or cannot flourish without cultivated assistance. Gardeners only need educate themselves as to which species imbibe more than their fair share of water. And for humans, flowering ornamentals provide the spirit-lifting color that most of our natives are lacking. No one should feel guilt when planting non-invasive introduced plants in our gardens. They are as worthy as non-threatened, cultivated Florida plants. Lest I be misunderstood, this does not mean that gardeners and especially nurseries do not have a serious responsibility to cultivate species which are not likely to become pests and to eliminate those that already are. Avoid nurseries which insist on providing invasive species whose weedy nature makes them cheap to grow (and expensive for you to remove). Some enlightened environmental groups are taking a fresh look at the value of cultivated trees where native habitat has already been destroyed. Now they see the value in protecting shade-coffee farms which are being replaced by high density coffee plantations because the shade trees provide habitat to many species of endangered migrating song birds. Madre de café is the name given to shade-giving species like Gliricidia or Inga spp, legumes which also naturally enrich the soil with their nitrogen-fixing roots. Because of a relatively few invasive species, a naiveté is afield that lumps together all introduced species as somehow out of balance with nature. Anyone willing to be open-minded can easily observe how introduced species now play a vital role in the conservation of native animals, birds and the quality of our life and greatly benefit the environment in general. There are some pretty misleading notions about the higher value of cultivating native plants. (How about that for a non-sequitur!) Every species is a vital cog in the engine of biodiversity. Every species contributes unique DNA to the gene pool from which we may one day derive yet unknown chemicals and medicines. Many cultivated tropical species are already extinct in their native habitat and exist only in captivity. The rainforests of the world are expected to last only a few more decades at most. Plant species around the world will only be preserved through cultivation just as we conserve tigers and other threatened animals in zoos. Botanical gardens by themselves cannot preserve all threatened species. In a world that is changing at a rate beyond human control, introduced species are filling many niches in their adopted landscapes. It is essential to understand that the word "native" must be used in the context of a plant within its habitat. Plants that are native to local habitats are not, simply by right of their proximity, "native" to a nearby habitat. A Keys plant like the mahogany is not native to Miami and a cypress in not native to the rock-pineland. Some ferns are only native to specific sinkholes. Further, planting "native" species in suburbia may or may not contribute to the viability of animal species in what, at best, could only be a highly fragmented system. Many animals depend on continuity of territory without roads and fences. All plants are created equal when it comes to conserving energy, and all play water conservation roles. They provide cooling shade, animal habitat and nourishment. They control topsoil and moisture distribution, preventing desertification (areas denuded of vegetation turning into desert). They enrich the soil, cleanse the air and convert carbon dioxide (a major culprit of global warming) into a fixed form, producing oxygen in the process. We must evaluate introduced species for their good as well as their bad qualities without prejudice. Destruction of native habitat cannot be and will not be corrected by planting Florida species in our gardens and along our streets. We don't yet know if we will be able to preserve native habitats indefinitely and the prospects are, frankly, not promising. It is imperative that we recognize that cultivating a wide variety of species is the only way to guarantee choice in the future. Kirsten Llamas is a botanist and photographer in Miami, Florida. Reprinted with permission from the Fall 1998 issue of 'Tropical Flowering Tree Society.' Back to Table of Contents
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