Some years ago, I planted a small butterfly bush in front of our
house just outside Philadelphia. Within a year or two, I regularly counted a
dozen or more butterflies at a time, including the swallowtails and cabbage
whites that frequent our area, perching like miniature artworks on this now-tall
bush with showy flower spikes, some upright, some gracefully drooping. Although
butterfly bush is not native to the western hemisphere, I’ve discovered a wealth
of native (and other exotic) plants that attract butterflies as well as
hummingbirds and bees.
What do butterflies, hummingbirds, and bees have in common? And
why would we want to attract them to our gardens, other than for sheer aesthetic
pleasure? The large group of animal species known as “pollinators,” which
includes various insects, birds and other wildlife, is unrelated except through
their ecological role of pollinating most flowering plants (including trees.)
This role is critical to humans because an estimated third of our food supply,
as well as some of our fibers and medicines, depends on these pollinators.
We’re aware of the threats to some of these species, such as
monarch butterflies. A less-recognized problem is that many other pollinators,
including native bees and honeybees (introduced from Europe, Africa and Asia),
also suffer from declining populations. Among the factors contributing to these
declines are improper use of pesticides, habitat loss or degradation, disease
and competition from non-native species. As pollinator populations decline, so
do the plants and trees that require them for pollination – and thus
reproduction – and the complex networks of whole ecosystems can be disrupted.
So how can we help out these animals so they can continue to
help us? We can make our gardens – large or small, urban, suburban or rural –
good sources of food and shelter for pollinators. In return, we can see and
literally taste the fruits of their labor, enjoy the pure delight of watching
them and know that we are protecting our local ecosystems.
Make your
garden pollinator-friendly
Avoid using pesticides, even “natural” ones such as Bacillus
thuringiensis (Bt).
Choose old-fashioned varieties of flowers whenever possible, because
breeding has caused some modern blooms to lose the fragrance and/or
nectar needed to attract and sustain pollinators.
Design your garden so that there is a continuous succession of
plants flowering from spring through fall – check for the species or
cultivars best suited to your area.
If you decide to use plants that aren’t native to your region,
choose ones that don’t spread easily, since these could become
invasive.
To provide puddles as a water source for butterflies (and other
welcome visitors) without letting them become a mosquito breeding
area, either refill containers daily or bury a shallow plant saucer
to its rim in a sunny area, fill it with coarse pine bark or stones
and fill to overflowing with water. Butterflies can drink from the
cracks between the filler but mosquito larvae have a difficult time
becoming established.
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What pollinators need to thrive, like most
creatures, are sources of water and food as well as shelter from harsh weather
and predators. In many cases, the plants and trees we cultivate and other
habitat elements we provide are beneficial to multiple pollinators. Pollinator
species and the native plants they’ve evolved with often occur only in certain
regions, so a good way to figure out what plants will most effectively attract
them to your own garden is to simply observe pollinators in local parks or weedy
areas.
Butterflies
General requirements for butterflies are
plants for their caterpillars to feed on and large clumps of small,
sun-loving flowers to provide nectar for adults. These plants include
zinnias, marigolds, tithonia, buddleia, milkweeds, verbenas and most herbs
if they are allowed to go to flower. Keep in mind that the caterpillars of
many butterfly species feed on only one or a few plant species (though those
plants may feed other species as well,) while some caterpillars feed on many
species. Milkweed, for example, is a food source for monarchs and other
butterflies, and is the sole food source for monarch caterpillars. While
monarchs have a very restricted food source, eastern tiger swallowtails feed
on tulip trees and lilacs, among a number of trees and bushes.
Besides food sources, some patches of long
grass for egg-laying, open patches of damp soil or sand for nutrition and
some flat stones in an open, sunny area for basking will provide a welcoming
habitat for these gorgeous creatures. Beautiful and elegant as they are,
butterflies are known to feed on animal carcasses and dung, which, along
with sand, provide essential salts and other nutrients. To provide these,
you can create an artificial puddle and “spike” it with mineral-rich sea
salt and dung (see instructions, right).
Bees
Attracting local bees, or encouraging the
ones already in your location, isn’t hard. While honeybees and some bumble
bees are social, living in colonies with a queen, most of the several
thousand bee species in North America are solitary, meaning that most
females build their own small nests. Many bee species prefer to nest in
exposed, sandy, well-drained soil in sunny areas, while others prefer piles
of branches, untreated lumber with nail or beetle holes, pithy stems or
hollow reeds and bamboo – all of which should be kept dry. Mud with nearby
water sources attracts mud-nesting bees, while unshaded, south-facing sandy
banks, especially in cold climates, attract bees that nest underground; dry
adobe walls and shallow caves attract other species. Bumble bees usually
nest in abandoned field mouse nests, found in undisturbed areas such as
woodlots, hedgerows, old barns and brush or compost piles. Hundreds of
flowers species attract bees, of course, especially purple and blue ones,
but don’t overlook such humble flowers as the dandelion and clover, which
thrive and blossom with no work on our part! As for stinging, which only
females can do, most bee species aren’t aggressive and generally ignore
humans.
Hummingbirds
Hummingbirds, which have been called “the
flowers of the air,” are found only in the western hemisphere. Of the 340
known species, only the ruby-throated hummingbird is found regularly east of
the Mississippi. Their feeding on flower nectar while hovering is well
known, but few people realize that they also eat tiny insects and spiders.
In fact, one more reason to avoid pesticides is the possible starvation of
hummingbird nestlings if not enough insects are available – and sprayed
pesticides can be directly lethal to these birds.
Hummingbirds visit flowers in both sun and
shade, and while they are certainly attracted to tubular red flowers, they
feed on other types as well – butterfly bush (buddleia) is a magnet for
hummingbirds. Besides flowering plants, hummingbirds, like many birds, need
shrubs or trees with dense foliage to provide shelter from predators and
places for nesting and perching; they also need a source of water. If you
use a hummingbird feeder, fill it with sugar-water (not a honey solution,
which can support fungi that are fatal to hummingbirds); clean and refill
the feeder every three to five days.
What to Plant
The tables below list annual and perennial plants
that attract butterflies and/or hummingbirds and/or bees, but don’t forget
that the flowers of trees and shrubs also provide nectar for these
pollinators, as well as nuts and berries for many other birds and mammals.
For example, spicebush (Lindera benzoin, whose leaves produce a delightful
but delicate scent when crushed), sumac (Rhus species) and viburnums (Viburnum
species) provide nectar for adult butterflies and bees as well as leaves for
butterfly and moth caterpillars.
The National Academy of Sciences is
currently conducting a study to document the status of pollinators in North
America and to recommend actions to reverse their decline. In addition, a
number of groups worldwide, including the North American Pollinator
Protection Campaign (NAPPC), are working to conserve pollinators and their
habitats and to educate the public about them.
If you’re committed to maintaining a habitat
for pollinators and other wildlife, you can apply for wildlife habitat
certification (and the associated bragging rights) through the National
Wildlife Foundation. Even planting a small area of pollinator-friendly
plants may provide critical refueling for some migrating butterfly or bird,
or a hard-working bee, so plant and then sit back and enjoy.
The butterflies and other wildlife are now
frequenting our yard, and I’m consciously adding perennials and other
elements to my garden that will sustain the pollinators that bring so much
pleasure to our eyes (and organic produce to our table), a mutualism I
expect to continue through the years.
Learn More
Butterfly Gardens: Luring Nature’s
Loveliest Pollinators to Your Yard by Alcinda Lewis, editor (Brooklyn
Botanic Garden Publications, 2006)
Butterfly Gardening: Creating Summer
Magic in Your Garden by The Xerces Society & Smithsonian
Institution (Sierra Club Books, 1998)
www.nwf.org/backyardwildlifehabitat/attractspecificwildlife.cfm
www.pollinator.org
www.monarchwatch.org
www.ars.usda.gov/Main/docs.htm?docid=12052
www.bbg.org/gar2/topics/wildlife/index.html
www.plants.usda.gov/
www.usna.usda.gov/Hardzone/ushzmap.html
www.rubythroat.org/GardensHummerMain.html
www.plantfacts.osu.edu/web
www.usna.usda.gov/Gardens/faqs/InvasivesAlternatives.html
http://nativeplants.evergreen.ca/
Author Robin Eisman is a
volunteer with the North American Pollinator Protection Campaign (NAPPC).
Visit their website at http://www.nappc.org.
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