Additional Information about Asclepias curassavica

Tropical Milkweed (Asclepias curassavica) can be dangerous to monarchs. Unlike native milkweed that dies back in the winter, tropical milkweed persists year-round in warm climates like our valley. This constant presence allows harmful parasites and diseases to build up, potentially disrupting migration patterns and sickening the butterfly population. The protozoan parasite Ophryocystis elektroscirrha (OE) is easily spread on tropical milkweed and because the plant doesn't die back in winter, parasite spores accumulate on the leaves over multiple generations. Caterpillars eat these spores and are born infected, leading to reduced lifespans, poor mating success, and flight defects. 

What to do: Plant native varieties like Showy Milkweed (Asclepias speciosa) or Narrowleaf Milkweed (Asclepias fasicularis). If you already have tropical milkweed in your landscape then trim the plant down to a few inches tall in the fall and winter months (around October or November depending on your zone). This forces the plant to regrow fresh, spore-free foliage and prevents monarchs from staying too long.