University of Vermont Extension
Department of Plant and Soil Science
BUTTERFLIES NEED OUR HELP
Dr. Leonard Perry, Extension
University of Vermont
Monarchs—those beautiful orange
butterflies we’ve seen all around in late summer in past years—are becoming
scarce. This is due in large part to loss
of habitat—both where they overwinter in Mexico and summer in the U.S., as well
as some recent temperature extremes.
While we can’t do much about the weather, we can help monarchs by
restoring their habitats and food they require to survive and reproduce.
Monarch butterflies overwinter in a
unique forest habitat in central Mexico.
Ecotourism, illegal logging, and natural disruptions such as fire or
disease threaten this small region where all the monarchs overwinter. Since record keeping began in 1994, their
numbers peaked at an estimated one billion in 1996, compared to an estimated 33
million during the winter of 2013-2014.
During this winter, only 1.65 acres were covered with monarchs, compared
to 51.8 acres in 1996.
After winter, monarchs migrate to
the southern U.S. states where they breed.
They have 3 to 5 generations per year, each generation only living 2 to
6 weeks, except the last. The final
generation that migrates up to 2,500 miles back to Mexico can live up to 8
months. It is the successive generations,
after the first, that migrate north and that we typically see there in mid to
Understanding how they feed is a key
to how we can help monarchs. While the
adult butterflies are “generalists” and can feed on the nectar of a variety of
flowers, the caterpillars (or larvae, that of
course latter change into the butterflies after forming a “chrysalis”) are
“specialists” feeding only on milkweed. Female butterflies use visual and
chemical cues to locate milkweed plants for laying their eggs. They seldom lay
eggs on other plants if there are no milkweeds, as the larvae that hatch will
Much of the “breeding” ground or
habitats of the monarch in this country have been lost. In populated areas, this has been due to development
and loss of the important milkweeds, replaced by either paving or manicured
landscapes. Over half the monarchs that
end up migrating back to Mexico have done so historically from the central
states or “corn belt.” Milkweeds have
been decimated in these areas from the increased use of weed killers on
herbicide-tolerant (GMO) soybeans and corn, and the increased production of
these for biofuels. Couple these factors
with a changing climate of extremes, including cold and wet springs and summer droughts,
and many fewer have bred and returned to Mexico.
Based on these facts on the monarch
butterfly habitats and needs, here are ways you can help these beautiful
pollinators. In your community,
encourage local towns, property owners, and farmers to delay mowing areas with
milkweeds until fall. This is especially
important in late summer when the migratory generation is developing.
Also encourage local, state, and
corporate officials from spraying pesticides and herbicides in monarch habitats
(particularly those with milkweeds) along roads, railroads, and powerline
right-of-ways. Especially avoid spraying
for insects when monarchs are present.
These same practices apply in home
landscapes. In addition, you can plant
butterfly gardens and plants using native milkweeds and nectar plants. A key is site selection—it should be in full
sun (at least 6 hours or more a day), sheltered from wind, and with
well-drained soil. Swamp milkweed is an
exception to most butterfly plants, as it will take poor drainage and
For eastern states, milkweeds to
consider include the butterfly weed (Asclepias
tuberosa), common milkweed (A.
syriaca), and the swamp milkweed (A.
incarnata). Annual flowers for nectar include
Indian blanket (Gaillardia pulchella),
lantana, Egyptian star flower (Pentas
lanceolata), Texas scarlet sage (Salvia
coccinea), Mexican sunflower (Tithonia),
and zinnia. Most other annual salvia are
attractive to pollinators too, except perhaps the common scarlet sage bedding
plant (Salvia splendens).
Perennial flowers that should grow
for more than one year include fennel (also a host for the black swallowtail), Joe pye (Eupatorium
purpureum), tall garden phlox (Phlox
paniculata), ironweed (Vernonia),
sedum, and purple coneflower (Echinacea purpurea). When choosing flowers, particularly from
groups like the coneflowers which have many selections with double or frilled
flowers, try to include species rather than cultivars (cultivated
varieties). Species often contain more
nectar and may be more attractive to pollinators like the monarch.
There are many resources to learn
more details on these topics, and to help monarchs as well as pollinators in
general. The Xerces Society (www.xerces.org)
works to help all pollinators, and offers a book (Attracting Native Pollinators) as well as a pollinator habitat sign
for purchase. Journey North (www.learner.org/jnorth/monarch/),
while designed for kids, offers much easy to read information on all aspects of
monarchs, and the chance to be involved in “citizen science” with tracking
migration. Perhaps the most extensive
resource is Monarch Watch (www.monarchwatch.org). Begun in 1992, this non-profit organization
based at the University of Kansas provides information, products (even
milkweeds) and a Monarch Waystation certification program (www.MonarchWatch.org/ws).