Tropical Milkweed – All I Know

Tropical Milkweed, Asclepias curassavica, also called blood flower, is one of my favorite annuals to grow in the St. Louis area.

It’s not only a host plant for monarchs, but is also an attractive nectar plants for the fall migrating monarch butterflies.

It’s hard to find the seeds or plants in most nurseries, so I usually save seed from the prior year. Online sources of seed are listed at the bottom.

I prefer to start my seeds in individual containers or plastic 6-packs.

Germination
Outside in the soil in spring, seeds took 11 days to germinate. Inside on a heat mat, covered with a plastic cover, seeds will start to germinate in five days.

Sunshine
TM likes lots of sunshine, so I like to put it in a sunny area with little if any competing plants.

Growth
TM takes a while to get growing since it’s a tropical plant, so there’s no big rush in getting the plants in the ground. They also seem to do better in good garden soil.

Pollination
Here’s an article on milkweed pollination – it’s a very complicated process. I tried to do it myself, but didn’t have any luck.

Aphids
Besides monarchs, aphids love milkweed. At times you will see your plants covered with aphids. Since I can’t use pesticides, the only way I can discourage them is spray them with water from the hose. Luckily aphids seem to have a limited life-span and they will just disappear if you wait long enough.

Varieties
There are some different varieties and colors, but they are all basically the same.

Tips
1. As the plant gets larger you can cut off the top to encourage branching.  This doesn’t always work.
2. TM will root itself in water if you cut off a big cutting.

Comparison to Perennial Milkweed
While I have tried numerous “perennial” types of milkweed in the past, they have all disappointed me over time. They usually don’t last more than two years.

Online Seed Sources

Everwilde.com

Swallowtail Garden Seeds

Burpee.com

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Filed under Milkweed, Monarchs

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