We grow tropical milkweed as a supplemental host plant to feed both early and late season Monarch caterpillars. It has proven to be a life saver. We have not experienced an issue with it inhibiting Monarchs from migrating, nor it being a source of OE because it naturally dies back in the winter as our habitat is in hardiness Zone 7. We always use new plants each year just to be sure.
We are aware of and have read various research studies discussing the pros and cons of tropical milkweed. Some experts are opposed to using it, and we appreciate and understand their position. However, we question how much experience do they have in actually raising Monarch caterpillars. Which is more credible: a scientist who has no practical experience raising caterpillars or someone who has done so for decades? We think the answer is both are credible sources of information.
Based upon our observation and experience–as well as from others who do raise Monarch caterpillars in North Carolina–the benefits are too great to deny–especially when native food sources are not available. We feel it is better to feed hungry Monarch caterpillars this milkweed as opposed to letting them starve to death.
How Monarch caterpillars are raised is a contributing factor to the spread of OE. The best practice is to let them raise themselves on their host plant. If you want to provide support by hand-raising it’s important to use good rearing practices such as sanitizing all rearing containers between brood cycles; disinfect host plants leaves if you live in an area where tropical milkweed doesn’t die back; remove chrysalises from rearing containers so the butterfly does not eclose in the presence of caterpillars; overcrowding the rearing container or attempting to raise every egg or caterpillar found on your plants; use only plants you grow yourself or from trusted nurseries.
This species of milkweed is a fast grower and quickly rebounds from being eaten by hungry caterpillars. It tolerates neglect and grows well in pots.
Is Tropical Milkweed Killing Monarch Butterflies? from Monarch Butterfly Garden. The author addresses the issue and writes from practical experience.
Monarch Joint Venture has a downloadable PDF fact sheet providing information.
Monarch Joint Venture also has an excellent Q&A about tropical milkweed.
Tropical milkweed impact on Monarch butterflies “vastly overblown”, says longtime butterfly researcher from Texas Butterfly Ranch
OE – Ophryocystis elektroscirrha – Monarch Butterfly from Butterfly Fun Facts, by Edith Smith of Shady Oak Butterfly Farm is a comprehensive article about how to rear Monarchs from egg to adult to limit and prevent OE