Tropical Milkweed for Monarchs and More
Asclepias curassavica milkweed has several common names including Tropical Milkweed, Bloodflower, Scarlett Milkweed, and Mexican butterfly weed. There are many other types of milkweed but this milkweed is one of the Monarchs favorite host plants.
Care of Asclepias Curassavica
Tropical milkweed is a perennial only in zones 8b-11. It is originally from South America but has naturalized in our tropical zones. Elsewhere in the US and Canada it is grown as an annual because it is a fast grower and flowers all summer and into the fall.
Asclepias curassavica prefers full sun but can handle a little shade. They can grow from 3-5 feet tall depending on conditions. You will get the best performance from Bloodflower if planted in full sun and moist well-drained soil. However, it can also tolerate some dryness once established.
Tropical milkweed can also be planted in containers and even kept indoors over winter if you have a bright sunny place for it. It will remain evergreen all winter indoors. In zones 9b-11 it will remain evergreen outdoors. It will die back to return in the spring in zones 8b-9a.
If you live in zones 9b-11 where it stays green all winter it is recommended by most Monarch researchers to cut it back in the winter so new growth will form or to not plant it at all in these areas. The reason is that Monarchs can get a parasite called OE and this parasite can survive on the leaves of any milkweed. So, if a milkweed does not die back and get new growth then the OE may stay present and continue to re-infect other Monarchs from year to year.
This is not an issue in areas where Tropical milkweed (or any other milkweed for that matter) does not stay green all winter.
Tropical Milkweed Plants for Butterflies
Asclepias curassavica is a Host Plant for two butterflies, the Monarch butterfly and the Queen butterfly. The Monarch butterfly can be found all around the US and into Canada. The Queen butterfly is found in Florida, our southwestern states, and down into Mexico.
Not only will Asclepias curassavica attract egg-laying Monarchs, it is also extremely attractive to all kinds of butterflies as a nectar plant. That is part of what makes milkweed such a great plant in the garden. In my garden it is especially attractive to the larger varieties of butterflies such as the Swallowtails.
When using Tropical milkweed to raise Monarchs indoors, you can simply break some leaves off and put them in a container with the caterpillar. The leaves will stay good for about 24 hours without water. We usually raise our Monarchs in large clear plastic containers. I just change out the old leaves and the frass (caterpillar poop) everyday and replace with fresh leaves.
You can also keep the leaves good for several days by putting them in a baggy in the refrigerator. This way you can give your friend, neighbor, school, etc, a caterpillar and some food without having to bring them fresh food each day.
Starting Asclepias curassavica from Seed, Propagation
Tropical milkweed flowers prolifically so there is plenty of seed to collect for the following spring and share with friends. Milkweed flowers produce pods that open up revealing seeds attached to white fluff that blows around in the wind. If you remove the pods once they have dried and just started opening then you can strip the seeds off pretty easily.
Asclepias curassavica seeds do not need to be cold stratified (since it is a tropical plant). You can start these indoors about 4-8 weeks before the last frost. Plant the seeds about 1/4 inch deep and keep moist. They will germinate in about 2-3 weeks. They can go outside after the danger of frost has past. Plant them about 18-24 inches apart. I usually plant mine about 18 inches apart. You can pinch these back to make a fuller plant.
Tropical milkweed seeds can also be direct sowed in the spring. In the South you can sow the seeds in the fall if you wish. They like warm soil so germination could be slow or erratic until the soil warms up.
This milkweed can also be grown from cuttings. I do not personally have experience with this but it is a common way of propagating Asclepias curassavica.
Tropical Milkweed Seeds and Plants
Asclepias curassavica is a very popular butterfly garden plant because it has so many great characteristics. It grows fast, flowers readily all summer, is a host plant for Monarchs, and it is extremely attractive to other butterflies as a nectar plant. I hope you will consider planting some for your butterflies!