In my Backyard

The wrong milkweed!

I planted milkweed to entice butterflies and to support an endangered species by providing food, shelter, and host plants for their caterpillars. Last week, I figured out that I had planted the wrong milkweed. Not just a little bit wrong, or kinda unhelpful – I planted a type of milkweed that is actually contributing to the rapid decline of the Monarch species world wide. After I recovered from my initial horror and dismay, I came up with a plan.

Before I go into my plan, let me explain the problem with this milkweed plant:

Monarch butterflies rely on several seasonal cues to begin migrating, one such critical cue is the dieback of their host plant in fall. Native species of milkweed all do this – even in Florida. However, the Tropical Milkweed plant is a non-native specie of milkweed with beautiful, showy flowers that bloom all year long.

When Monarchs come across this big, beautiful, tasty milkweed plant, they tend to settle in for the winter rather than continuing their migration. This pattern (or anti-pattern) has resulted in catastrophically high disease infection rates among Monarch butterflies in Florida. The worst of which is caused by a protozoan parasite, Ophryocystis elektroscirrha, or OE for short. Over 70% of the Florida Monarch population is heavily infected by OE (Project Monarch Health).

The images above (taken by Chip Taylor) show scanning electron micrographs of parasite spores clustered on abdominal scales from a parasitized monarch. Project Monarch Health.

OE requires a host body to reproduce but once it does, it produces spores that can live outside the host body. These spores can then be spread from the adult butterfly to the milkweed plants that get eaten by caterpillars. Once inside the body of the caterpillar, the parasite’s life cycle begins again.

I’ll spare you the heartbreaking images of the seriously sick and infected butterflies and skip ahead to the proactive, problem-solving part of this post; my plan to fix my mistake and plant native milkweed:

Step number 1: remove any and all seedpods from the tropical milkweed plants and dispose of them so the seeds cannot grow.

Step number 2: monitor the caterpillars already on the current milkweed plants and collect any chrysalises I find. I’ll bring these inside and monitor them for signs of OE. The Monarch Health Project has instructions for testing butterflies for OE here.

Step number 3: Remove all the tropical milkweed and replace it with native milkweed species.

Well, I’ve removed all the seed pods, and I’ll keep doing that until either 1; it gets cold enough that I can simulate a “dieback” of the milkweed plant by cutting it back, or 2; I’m reasonably sure I won’t be unnecessarily killing a bunch of caterpillars. If I can find any chrysalises, I’ll collect them and in the meantime, I’ve been researching native milkweed varieties.

Identifying and locating native milkweed varieties has turned out to be more difficult than I anticipated. However, I want to give a shout out to Twig and Leaves our local native plant nursery in St. Petersburg! They are great! I got six milkweed plants and a bunch of other really great native plants that all kinds of pollinators love. I highly recommend stopping by if you’re looking for native plants and want to build a pollinator garden. Don’t let the slightly confusing storefront stop you – the door sticks a bit but it’s ok to just go right in.

After a lot of searching, cross referencing, and reading, I realized part of the difficulty is the sheer number of different plants in the genus Asclepias. I started making a spreadsheet to keep track of them all and then I found this fantastic site: The Atlas of Florida Plants Institute of Systemic Botany They have a great database with plenty of very helpful links. Here’s a pdf version of my search for native milkweeds of florida.

Here’s a pdf of information on native milkweeds put together by the Xerces Society:

Here’s a pdf of information on native milkweeds put together by Monarch Joint Venture:

So far, I’ve only been able to find a few of the milkweed varieties on this list:

Swamp Milkweed (Asclepias incarnata). Photo by: Andrew C

Swamp Milkweed (Asclepias incarnata)

Plant care: this plant can grow 4-6 feet tall and requires full sun and consistent moisture as its natural habitat is wetlands. USDA plant fact sheet.

I purchased six swamp milkweed plants at Twig and Leaf nursery. The nursery owner assured me I can mix peat into the sandy soil I have to increase moisture retention. Right now they have died back to small stalks but hopefully, these will start growing again this spring.

Butterfly Weed (Asclepias tuberosa)

Plant care: this plant can grow to about 36 inches tall and is a very hardy plant. Once established, it will tolerate hot, dry conditions in poor sandy soil. Though it may not produce blooms for the first couple years, once it is established, it is very drought tolerant. (Gardening How How).

The seeds for this variety of milkweed are fairly easy to come by. I have already ordered some through a vendor on Etsy.

Whorled Milkweed (Asclepias verticillata)

Plant care: this plant can grow to about 2-3 feet tall and is a very hardy, vigorous plant. Once established, it will tolerate hot, dry conditions in poor sandy soil. It can spread through rhizomes so you may want to consider a plan for containment if you are concerned about it spreading. (New Moon Nursery).

The seeds for this variety of milkweed are somewhat easy to come by and I recently saw a listing for a live plant as well. I have already ordered some through a vendor on Etsy.

Green Milkweed (Asclepias viridiflora)

Plant care: this plant can grow to about 18 – 24 inches tall and grows best in full sun with well draining soils. (Grownative.org).

I thought I had ordered this plant, but after combing through all this info., I realize I ordered Asclepias Viridis – this plant has a few common names including “Antelope Horns milkweed”, “Spider Milkweeed”, and “Green Milkweed”. You’d think I’d know better than to go by common names by now wouldn’t you?

Well, I did find a few vendors selling seeds for this plant on Etsy and a couple other sites online, but wow! This must be a rare plant because the seeds are not cheap! Maybe I’ll give this one a try another year.

Well, I have three different species of milkweed to replace my tropical milkweed with – I think that’s enough to be going on with. I’m heading out to the yard now to get to work planting! I’ll post updates as things progress.

References:

Jepsen S., Schweitzer D.F., Young B., Sears N., Ormes M., Hoffman Black S.. March 2005. Conservation Status and Ecology of the Monarch Butterfly in the United States. Prepared for the U.S. Forest Service by: NatureServe Arlington, Virginia and The Xerces Society for Invertebrate Conservation Portland, Oregon. https://www.xerces.org/publications/scientific-reports/conservation-status-and-ecology-of-monarch-butterfly-in-us.

Journey North. https://journeynorth.org/monarchs/resources; Date accessed 10/20/21.

Nestle, R.; Daniels, J.C.; Dale, A.G. Mixed-Species Gardens Increase Monarch Oviposition without Increasing Top-Down Predation. Insects 2020, 11, 648. https://doi.org/10.3390/insects11090648

Project Monarch Health. https://www.monarchparasites.org/oe; Date accessed 10/20/21.

Wade L. January 13, 2015. Plan to save monarch butterflies backfires; The wrong kind of milkweed is stoking parasite infections. Science.org. doi: 10.1126/science.aaa6337

Williams, M.J. 2015. Monarchs Make Florida Home. Natural Resource Conservation Service of Florida, https://www.nrcs.usda.gov/wps/portal/nrcs/detail/fl/newsroom/releases/?cid=NRCSEPRD363613. Date accessed 10/20/21.

Xerces Society for Invertibrate Conservation. Monarch Butterfly Conservation. https://xerces.org/monarchs. Date accessed 10/20/21.