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.
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.
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
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!
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).
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.
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.
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.
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.
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.
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).
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.
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.
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.
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
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.
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.
Llamas is a botanist and photographer in Miami, Florida. Reprinted
with permission from the Fall 1998 issue of 'Tropical Flowering
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