Milkweed for Healthy Monarch Butterflies
Aquatic milkweed Asclepias perennis
One of many native milkweeds
Tropical milkweed Asclepias curassavica
Harmful to monarchs
Newly hatched monarch butterflies in some back yard environments, particularly in warm coastal areas, have been found to be unhealthy when the wrong kinds of milkweed plants are grown to feed the caterpillars. The newly-hatched butterflies suffer from a debilitating parasite called OE (Ophryocystis elektroscirrha). According to Candice Annen of the Monarch Stewards Program, "one of the main reasons OE spreads in coastal areas is the predominant use of tropical milkweed (Asclepias curassavica), a non-native plant species that doesn’t naturally die back in the winter. Tropical milkweed (Asclepias curassavica) can also interfere with monarch migration and reproduction."
The whole explanation appears in a recent blog post from Annen through her blog "Misadventures with milkweed" entry at the National Wildlife Federation. She describes her learning curve, from a passionate amateur raising increasing amounts of milkweed in her back yard for monarch caterpillars, to researcher in order to learn what was ailing the newly hatched monarchs that were "unhealthy, deformed, weak, and unable to fly." Distressed at the vision of these dead and dying butterflies, she did a lot of research and outreach and learned that the variety of introduced milkweed was the problem.
Sharing this kind of experience and research helps us help our organic family adjust their landscaping to benefit the monarchs they want to support. Find out what kind of milkweed you're growing, and if needed, change it to an acceptable variety. Below are some links to information about North Texas native milkweed and the monarchs it supports.
Project Milkweed from the Ladybird Johnson Wildflower Center https://www.wildflower.org/project/project-milkweed
This article from 2013 was written prior to the research into tropical milkweed. While the rest of the information is good, the author at the time preferred the tropical introduced plants and notes that butterflies preferred it - so this part of the article should serve as a warning - because they are drawn to it, the tropical milkweed needs to be out of your butterfly garden. It won't do them any good and it might cause harm. https://texasbutterflyranch.com/2013/04/25/got-milkweed-updated-plant-guide-for-central-and-south-texas/
Identification of Milkweeds in Texas, compiled by Jason Singhurst and Ben Hutchins