Swamp Milkweed vs Tropical Milkweed

The popularity of Tropical milkweed, also known as Mexican Milkweed or Scarlet Milkweed (Asclepias curassavica), a non-native species of milkweed, has skyrocketed due to its ease of propagation and attractive flowers and foliage. However, when planted in areas with temperate climates, it doesn’t die back in the winter, which can lead to problems with Monarchs migration. They tend to stay where the food source is and won’t travel.

According to many sources that support protecting the Monarchs,  Monarch butterflies that visit the plant can carry a parasite called Ophryocystis elektroscirrha, or OE, which can be deposited on the plant’s leaves. As caterpillars hatch and feed on the plant, they ingest the OE, which can have harmful effects on monarchs’ migration success, body mass, lifespan, mating success, and flight ability.

Unlike native milkweeds, which die back after blooming and take the parasite with them, tropical milkweed remains evergreen throughout the winter, allowing OE levels to accumulate on the plant. This can result in successive generations of monarch caterpillars being exposed to dangerous levels of OE.

It is recommended to use native Milkweed instead of Tropical.  Asclepias incarnata, Asclepias perennis and Asclepias tuberosa are all native milkweeds.