Butterfly lovers all over Southern California are eagerly searching for milkweed plants to attract monarch butterflies to their gardens. Because of habitat loss and pesticide use, the monarch butterfly population has dropped by 80% in the last decade, and suburban gardeners are pitching in to help provide habitat for these beautiful and iconic insects.
The most common commercially available milkweed for sale at garden centers is Asclepias curassavica, or tropical milkweed. It’s easy to grow, has pretty red and orange flowers, grows year-round, and is attractive to monarchs and plant lovers alike. It’s a garden center’s dream.
Unfortunately, it can be a monarch conservation nightmare.
The monarch parasite protozoan OE is spread when an infected female lays her eggs. OE spores are deposited onto the milkweed leaf, and the newly hatched caterpillar eats the spores as it eats the leaf. This infected caterpillar becomes an unhealthy adult, and the cycle continues until the milkweed goes dormant. When there are no more milkweeds available, monarchs migrate, but the infected butterflies do not usually survive the journey. When the milkweeds regrow in spring, they are clean and free of OE spores, and the cycle is broken.
Tropical milkweed does not die back in winter, allowing infected adults to continue breeding and reinfecting the same plant. Non-migratory populations are five times more likely to be infected with OE than those that migrate.
So many people have planted tropical milkweed that it is now common to see monarch butterflies in winter, and see monarch caterpillars long before the native milkweeds begin regrowing in spring. Butterfly lovers, desperate to save their winter caterpillars, plant the only milkweed that’s available, and the disease continues to spread.
Do not be discouraged, butterfly lovers. Although native milkweeds are harder to find and slower to grow, once established they’ll reward your persistence with healthier caterpillars that will know when to migrate properly.
When buying milkweed for your garden, remember:
Blooms pink or white help monarchs take flight.
Blooms orange and red help disease spread.
– Leslie Helliwell, ENC Butterfly Wrangler
Want to learn more?
Locally native milkweeds – Asclepias californica, Asclepias eriocarpa, and Asclepias fascicularis – become dormant and grow back at the right time — when monarchs have returned to the area. It is important to note that planting non-native milkweed is unwise, as it can disrupt migratory cycles and make monarchs more susceptible to parasites.
READ this great article and this article explaining why planting non-native tropical milkweed can be harmful to monarchs.
HERE is a page with links to several articles about monarchs and milkweed!
Check out our post on the Top Ten ways to help Butterflies.
HERE is an article describing in more detail why the ENC promotes the use of locally native plants.