Monarchs and Milkweed
The Monarch butterfly is in peril
Throughout Florida and the United States, habitat loss, the wide use of herbicides and genetically modified crops, and frequent roadside mowing have decreased the occurrence of milkweeds (Asclepias species), the Monarch’s host plant. As a result, the number of Monarch butterflies (Danaus plexippus) has plunged alarmingly.
Our love and concern for Monarchs has increased interest in milkweed. But one readily available non-native milkweed species appears to be doing harm.
Why plant native?
Florida’s native plants have evolved here over thousands of years. They have symbiotic relationships with the plants and wildlife around them, and have adapted to Florida’s unique climate, pests and soils. When the right plant is used in the right place in planned landscapes, they typically don’t need fertilizer, insecticides and additional water once established.
Butterflyweed (Asclepias tuberosa) is the most widely recognized native milkweed. Its showy clusters of bright reddish-orange flowers bloom late spring through fall. This native wildflower grows 12 to 15 inches high in a bushy form and has coarse lance- or oval-shaped leaves. Because it grows naturally in sandy habitats, it adapts well to dry landscapes.
Pink swamp milkweed (Asclepias incarnata) is found in moderate to moist sunny habitats, where it grows 2 to 4 feet tall. It blooms in summer with very showy light pink- to rose-colored flower clusters. Its fleshy linear leaves grow up to 6 inches.
White swamp milkweed (Asclepias perennis) is a shorter bushy plant growing to about 2 feet. Summer flowerheads are small with white to light-pink flowers. Bright green leaves are lance-shaped. It prefers moist to wet soil conditions and can adapt to shady locations.
DID YOU KNOW?
Queen and Soldier butterflies also use native milkweeds as host plants for their caterpillars, and Pipevine, Spicebush and Eastern swallowtails rely on them for nectar. Many other butterflies and bees — including native sweat bees, leafcutter bees and yellow-faced bees — need milkweed’s pollen and nectar.
Pictured: Pipevine swallowtail on Butterflyweed (Asclepias tuberosa) by Mary Keim
Nectar for Monarchs
Plant these natives along with native milkweed to provide nectar for Monarchs:
- Blazing star (Liatris spp.)
- Snow squarestem (Melantherea nivea)
- Chaffhead (Carphephorus spp.)
- Climbing aster (Symphyotrichum carolinianum)
- Frostweed (Verbesina virginica)
- Flattop goldenrod (Euthamia caroliniana)
- Goldenrod (Solidago spp.)
- Mistflower (Conoclinum coelestinum)
- Scorpiontail (Heliotropium angiospermum)
- Beggar’s tick (Bidens alba)
- Yellowtop (Flaveria linearis)
Why aren’t native milkweed plants widely available?
Although they are robust in Florida’s natural habitats, native milkweeds can be difficult to propagate. Because they are a larval food source, butterfly larvae may devour milkweed foliage before the plants can be brought to market.
What we are doing
The Florida Wildflower Foundation, along with partners such as the Florida Museum of Natural History and Florida Association of Native Nurseries, is working to increase native milkweed production by supporting the sustainable collection of seeds from wild populations and the testing of propagation methods in order to develop and share best practices.
Where to purchase native milkweed plants
Digging up wild native milkweed and collecting seed can reduce its ability to reproduce.
- Do not attempt to dig up wild native milkweed plants.
- Do not collect wild native milkweed seed unless you have permission from the landowner.
- If you have permission to harvest, take no more than 10 percent of the available seed.
How Tropical milkweed can harm Monarchs
Tropical milkweed (Asclepias curassavica) is native to Mexico and Central America. It is widely available at Florida’s mainstream nurseries and big box retail centers because it is easy to grow. However, the use of Tropical milkweed can harm Monarchs.
Harm from Insecticides. Commercially grown Tropical milkweed plants are sometimes treated with systemic insecticides to keep pests off of them, giving them a better appearance at retail nurseries. These insecticides can be very toxic to Monarch caterpillars that feed on the leaves, increasing mortality rates.
Harm from parasites. Tropical milkweed has been linked to the higher transmission of Ophryocystis elektroscirrha (OE), a protozoan parasite. When OE spores infect milkweed leaves, they can be carried on the bodies of adult butterflies, spreading the infection. Microscopic spores on are spread to eggs, and infected larvae may not emerge from pupal stage or may emerge as very weak adults.
Harm from migration disruption. Tropical milkweed remains evergreen and may bloom throughout winter, encouraging migratory Monarch populations to overwinter in Florida and continuously breed. This disruption of their natural life cycle makes them more susceptible to death from food shortages and freezing winter temperatures.
Overwintering Monarchs are also more susceptible to OE, which persists and accumulates in Tropical milkweed throughout the winter. (Native milkweed loses its leaves and goes dormant during the winter, eliminating the presence of OE.)
Although not documented scientifically, the higher concentration of cardenolides toxin in Tropical milkweed may adversely effect Monarchs. The plant has also escaped into natural areas, which may further disrupt migration paths.