Sally Scalera: Growing a non-native species of milkweed? Cut it back before Thanksgiving
If you’re growing a non-native milkweed, be sure to cut it back before Thanksgiving so monarch butterflies will migrate south instead of sticking around. Butterfly life cycle
Milkweed is the perfect plant for butterfly enthusiasts who want to attract monarch butterflies.
When a female monarch discovers the milkweed, she lays her eggs on it. Once the eggs hatch, the small caterpillars eat and molt, repeating that process again and again, until they form their chrysalis.
They complete their entire life cycle on or near the milkweed plant.
Monarch butterflies are unique, because they migrate south for the winter. It is important that they migrate every winter.
Native milkweed species are the best plants to grow, because they die back to the ground in the fall and don’t begin growing again until the spring. This is great for the monarch butterflies. When the plants disappear, they fly south.
Tropical milkweed (Asclepias curassavica), on the other hand, is native to Mexico and produces clusters of red and yellow tubular flowers throughout the year. In garden centers, it is often labeled as butterfly weed. If you are growing a solid yellow milkweed, your plant could be a yellow flowering form of our native butterfly weed, Asclepias tuberosa.
There is also Asclepias curassavica ‘Silky Gold’, Golden butterfly weed that produces yellow flowers. The easiest way to tell the two species apart is to snap a leaf off to see if it has a milky sap. If milky sap begins to flow, the plant is the non-native tropical milkweed.
When growing tropical milkweed, it’s important that the plant is cut down to protect the Monarch butterflies from disease. Some monarch butterflies have a protozoan parasite, Ophryocystis elektroscirrha or OE. When an OE-infected monarch visits a plant, some OE protozoans are deposited there. Caterpillars ingest protozoa, along with the leaf, when eating.
The level of OE can build up on a plant over time. Caterpillars that consume a lot of OE may not survive metamorphosis, and if they do, they may have reduced body mass, mating success, flight ability and life span. Many don’t survive migration.
The OE protozoa can be found on our native milkweeds also, but our native species die to the ground every fall, and the parasites die with it. Therefore, every summer the new monarchs feed on parasite-free foliage.
To provide the caterpillars with maximum protection, cut your tropical milkweed down twice, once in June and again anytime between Halloween and Thanksgiving. The first cutting will reduce the buildup of OE on the plant and the final one will keep the plant from blooming through the winter, so the Monarchs will migrate.
Another precaution to take when growing tropical milkweed is to prune off seed pods as they begin to form. This will also benefit the plants, because they won’t be expending energy to produce seeds but could instead grow and/or bloom again.
Recent research done by the University of Florida has also discovered that planting wildflowers and milkweeds together increases the number of monarch butterflies that are produced in the area. In the areas where other flowering plants were planted with the milkweed, they found the monarchs laid 22% more eggs.
Diverse plantings provide a greater benefit for a variety of organisms. Though the caterpillars need milkweed plants as their food source, the adult butterflies need more than just milkweed flowers as a nectar source, so diverse wildflower patches are more appealing to the adult monarch butterflies.
Florida has 24 species of native milkweeds, 11 of which are found in or around Brevard County. Florida native milkweeds can be found in a variety of soil conditions, ranging from very wet to very dry. Here are some native species that prefer to grow in dry sandy areas such as pastures, sandhills or along fence rows:
• Butterfly weed, Ascelpias tuberosa, has the largest native range and can be found throughout the eastern United States and a lot of the southwest, though not into California. This native species produces bright orange or yellow flowers that bloom from spring through the fall. It’s found in sunny and dry, upland sites that have sandy soil. Not only do the flowers attract bees and other pollinators, they also attract hummingbirds. The plants will grow 1 to 3 feet tall and spread 1 to 2 feet.
• Pinewoods milkweed, Asclepias humistrata, has been vouchered in Volusia, Orange and Osceola counties, so it is probably growing here in Brevard also. Find a sunny spot for this milkweed to grow one to three feet tall. The plants bloom beginning in the spring and continue through the summer, producing pink, lavender and white flowers.
If your yard has moist or wet areas, consider these native milkweed species:
• Whorled milkweed, Asclepias verticillata, is considered a small annual plant that grows best in sandy, moist areas that never get extremely dry. The showy flowers mix well with other wildflowers and will attract a variety of pollinators, in addition to the butterflies. A word of warning: This species is the most toxic of the milkweeds and is considered a weed where livestock graze.
• Swamp milkweed, Asclepias incarnata, produces showy, pink flowers in sunny locations. The plants grow in large clumps that reach 3 to 6 feet tall. This species is considered one of the most striking of the native species, and they will also attract our native bees.
Aquatic milkweed, Asclepias perennis, is another species that has been vouchered in Volusia, Seminole, Orange, Osceola, as well as to the west and south to the Gulf of Mexico. It produces white flowers and is a small-growing milkweed that grows in locations with partial to full shade.
There are a number of other native milkweed species that will be more difficult to find for sale, such as the Largeflower milkweed, Asclepias connivens, Curtiss’ milkweed, Asclepias curtissii, Florida milkweed, Asclepias feayi, Fewflower milkweed, Asclepias lanceolata, and Velvetleaf milkweed, Asclepias tomentosa.
If you want to start gardening for monarch butterflies, consider planting some native milkweed species, mixed with wildflowers. What a great way to beautify your yard and help the monarch butterflies too