Why You Shouldn’t Plant Tropical Milkweed for Monarchs
It’s in every garden center. It’s pretty, it’s cheap, and monarchs absolutely love it. So why do butterfly gardeners keep saying not to plant tropical milkweed? Because in warm places like Florida, it never takes a winter break — and that one fact causes a chain of problems for the monarchs you’re trying to help.
What tropical milkweed is
Tropical milkweed (Asclepias curassavica) is the red-and-yellow flowered milkweed sold at most garden centers. It’s not native to the United States. Monarch caterpillars will happily eat it, which is exactly why it sells so well — and exactly why the problem is so sneaky.
Reason 1: It lets a parasite build up
There’s a microscopic parasite called OE (Ophryocystis elektroscirrha) that infects monarchs. Infected adults scatter OE spores onto milkweed leaves, caterpillars eat the spores, and heavily infected monarchs emerge weak, with crumpled wings, unable to fly or migrate.
Here’s the key: milkweed that’s native to your area dies back in winter, and that dieback breaks the OE cycle — the spores go away with the old leaves. Tropical milkweed in Florida never dies back. It just keeps growing, and the spores keep piling up on the same plants, season after season. Gardens with year-round tropical milkweed have been found to carry much higher OE levels than gardens with native milkweed.
Reason 2: It confuses the monarchs’ calendar
Monarchs are supposed to migrate. But when fresh tropical milkweed is available all winter, monarchs keep breeding through the winter instead of migrating — and those winter butterflies tend to be weaker and more heavily infected. The great migration depends on monarchs getting the right seasonal cues, and evergreen milkweed scrambles the signal.
Reason 3: It’s not part of your local ecosystem
Native milkweeds evolved with your local soil, weather, pollinators, and seasons. Tropical milkweed didn’t. In warm climates it can also self-seed aggressively and spread where it wasn’t planted.
What to plant instead
Plant milkweed that’s native to YOUR area. In Florida, good choices include:
- Swamp milkweed (Asclepias incarnata) — our caterpillars’ favorite
- Butterfly weed (Asclepias tuberosa)
- Aquatic milkweed (Asclepias perennis)
Ask a local native plant nursery what’s native near you — that’s always the best answer, wherever you live. And give your adult monarchs nectar plants too: mistflower, goldenrod, and asters are all favorites.
Already have tropical milkweed? Don’t panic
No shame — garden centers sell it everywhere, and most people had no idea. You don’t have to rip it out today. What helps right now: cut it back hard in the fall, and again mid-season, to mimic the natural dieback and break the OE cycle. Then, as you’re able, swap it out for natives.
Monarchs need milkweed — just the right kind. Plant native, cut back what isn’t, and your garden becomes a genuinely safe stop for them.