By Julie Christensen
When we talk about milkweed and butterflies, we are usually talking about one butterfly in particular: the Monarch. Monarchs are fascinating creatures found in both eastern and western coastal regions of the United States. Adult monarchs migrate annually to Mexico. In the spring, they fly northward, stopping along the way to lay eggs. In a typical summer, 3 to 4 generations of monarchs may reach adulthood. The last generation doesn’t lay eggs, but flies south in the fall to overwinter in the mild forest regions of the Sierra Madre mountains in Mexico. Come spring, the cycle begins once again.
In recent years, monarch populations have declined due to several factors. Increased pesticide use often kills caterpillars before they can reach adulthood. Natural wetlands and fields, where milkweed grows abundantly, are disappearing, and with them, a major food source for monarch caterpillars, which eat only milkweed. Genetically modified corn crops are lethal to monarchs, as well. Finally, logging operations in the Sierra Madre mountain range have destroyed much of the habitat monarchs rely on to survive the winter.
You can help restore the monarch butterfly population by planting a butterfly garden that includes milkweed. When you think of milkweed, you probably remember common wild milkweed, with its large seed pods and green-gray leaves. If you have acreage, consider planting common milkweed, which grows quickly and produces large plants and fragrant pink or lavender flowers. On the other hand, common milkweed (Asclepias syriac) is invasive, especially in moist soils, and spreads through underground runners. Don’t plant it in a small garden. Instead, opt for a milkweed variety suited to your garden’s size and growing conditions:
- Butterfly weed (Asclepias syriaca) grows 2 to 3 feet high and thrives in full sun and somewhat dry conditions. It produces prolific clusters of neon-orange, red or yellow blooms. Butterfly weed is easy to grow and tolerates almost all soil types, as long as the soil is well-drained. It rots in soggy soil.
- For moister soils, try swamp milkweed (Asclepias incarnate). This plant grows 3 to 5 feet tall. The pink or white flowers bloom most of the summer, providing nectar for adult monarchs, as well as leaves for the green, white and yellow striped caterpillars.
- Scarlet milkweed (Asclepias curassavica) is a compact variety suitable for containers and pots. Its brilliant orange and yellow blooms provide a bright focal point in the garden.
- Whorled milkweed (Asclepias verticillata) is a native plant that tolerates dry conditions and poor soils. This compact plant produces greenish-white blooms and stays under 2 feet tall.
- Another native plant, showy milkweed (Asclepias speciosa) grows in fields and along rocky crags and marshes throughout the Midwest and western United States. Showy milkweed grows 6 feet tall and has silver-green leaves and rose-hued flowers. The plant is less invasive than common milkweed, but needs a lot of room.
You can buy nursery transplants at most nurseries in the spring, but if you want a lot of plants, try growing milkweed from seed. Most varieties need a cold stratification period to soften the seed coat and break dormancy. There are several ways to achieve this:
The first method is to plant milkweed seeds directly in the garden in the fall. Loosen the soil and rake it so it is even. Spread the seeds over the soil and cover them with 1/8 inch of soil. Another option is to stratify the seeds in your refrigerator. Mix the seeds with ¼ cup perlite, ¼ cup sand and 2 teaspoons hot water in a plastic bag. Label the plastic bag with the date and the type of seed and place it in your refrigerator for 3 months. Plant the seeds outdoors after the last expected frost.
If you’ve had trouble getting seeds to grow outdoors, there are two possible causes. Milkweed seeds are lightweight and may wash away in the garden. Another common problem is that of rodents eating the seeds. To prevent these issues, start seedlings indoors. Place the seeds in the refrigerator as outlined above in early winter. About 6 weeks before the last expected frost, plant the seeds in seed starting trays with a lightweight, soil-less starting mix. Spray the starting mix with water in a spray bottle to moisten it and cover the trays with plastic wrap. Keep the soil evenly moist, but not soggy. Once the seeds germinate and emerge, transfer the seed tray to a sunny window. When the plants stand 6 inches high, transplant them outdoors.
Check out the following resources to learn more:
Buy Milkweed Seeds from Butterfly Encounters
Plants that Attract Butterflies from the Morton Arboretum
When she’s not writing about gardening, food and canning, Julie Christensen enjoys spending time in her gardens, which includes perennials, vegetables and fruit trees. She’s written hundreds of gardening articles for the Gardening Channel, Garden Guides and San Francisco Gate, as well as several e-books.