Tropical Milkweed

Despite the bad rap it has gotten in the past few years, one of my very favorite flowers in the butterfly garden is Asclepias curassavica also known as Tropical Milkweed, Bloodflower, Scarlet Milkweed, and Mexican Butterfly Weed.

A female Monarch butterfly (Danaus plexippus) is nectaring on the bloom of this Tropical Milkweed.

There are many other types of milkweed but Asclepias curassavica is one of the Monarch butterfly’s favorite host plants. Here are eight reasons why it is my personal favorite milkweed.

1. Flowers bloom continuously from spring to fall in temperate climates and in tropical climates they will flower all year.

2. Asclepias curassavica is easy to grow from seeds and is a fast grower.

No need to cold-stratify Tropical Milkweed. Just add the seeds and watch them grow! Click here to purchase seeds.

3. You can also propagate from stem cuttings.

If you have potting soil and containers available, simply place the stems directly into the potting soil. Keep the soil moist until you start to see leaves sprouting from the nodes (the bumps on the stems where leaves used to be). At the same time, roots will be growing from the nodes underground. These are 4-inch (10 cm) nursery pots.

4. Tropical Milkweed is tolerant of different soil types,  growing well in dry, moist, and wet soils.

5. Tropical milkweed can be planted in containers.

Plant Tropical Milkweed in a large plastic or terracotta container for ease of moving. Also, if you grow the milkweed in containers, you can bring them inside to overwinter.

6. Asclepias curassavica attracts both Monarch and Queen butterflies because they use it as a host plant.

Queen (Danaus gilippus) and Monarch (Danaus plexippus) depositing eggs on Tropical Milkweed.

7. Many species of butterflies will nectar on the tropical milkweed flowers.

Tiger Swallowtail, White Peacock, Black Swallowtail, and Spicebush Swallowtail.

8. Hummingbirds also like to feed on the blooms.

Photo by Rhonda Cantu, used with permission.

Tropical Milkweed is a perennial in zones 8-11. It will grow year-round in zones 9b-11. In zones 8-9 it will die back to return in the spring. Elsewhere in the US and Canada, it is grown as an annual.

If you live in zones 9b-11 where the Tropical Milkweed stays green all year it is recommended to cut it back in the fall or winter so new growth will form. The reason is that Monarchs can get a parasite called OE. OE is a protozoan parasite that is spread to any milkweed plants when an infected adult butterfly flies over the plants. The flapping of monarch butterfly wings exfoliate the OE spores and the spores fall like glitter and stick to the milkweed. When a caterpillar ingests the leaves with the spores they become infected. These spores can survive on the leaves of any Milkweed. So, if Milkweed does not die back and gets new growth then the OE spores may stay present and continue to re-infect caterpillars. This is not an issue in areas where Tropical Milkweed (or any other Milkweed for that matter) dies back in the winter.

Tropical Milkweed should be cut back at least once a year about six inches from the soil.

Since I live in USDA Zone 9b where Tropical Milkweed lives year-round, I cut the plant back twice a year, once in mid-summer and again in late December or in January. I will also cut it back once it gets leggy. This does two things, one, it removes a build-up of OE spores on the plant that can be harmful to the Monarch, and two, it encourages branching and therefore produces a healthier plant and more flower clusters.

This wall of Tropical Milkweed growing in my garden attracts Monarchs, Queens, and many other butterflies.

Additional Resources:

Year 2023: What Does the Year Hold for Monarchs and Tropical Milkweed? by Kathy Keatley Garvey

Tropical Milkweed -Yes or No? by Edith Smith

Choice of Plant Reduces Parasitic Load: Tropical Milkweed

Tropical Milkweed and the Injurious Effects of Well-Meaning People by Jeffrey Glassberg

What is OE by Project Monarch Health

Tropical milkweed impact on monarch butterflies “vastly overblown,”says longtime butterfly researcher by Texas Butterfly Ranch

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