Tropical milkweed is not native, but it is widely available at garden centers in one-gallon pots and it also germinates easily from seed and cuttings. As much as I support native plants, this is my favorite Monarch host plant. It’s easy to grow, not a water hog, propagates easily from seeds and cuttings, blooms prolifically and draws Monarchs like a magnet. Commercial butterfly breeders and even organizations like Monarch Watch rely on Tropical milkweed to raise butterflies in captivity.
The plant can be controversial for native plant purists and some scientists. Theories abound on the appropriateness–or not–of Tropical milkweed in Central and South Texas.
The plant originated in Central America and has gradually moved north. Dr. Chip Taylor, founder of Monarch Watch, points out that Tropical milkweed is the plant on which Monarch butterflies evolved.
In my completely unscientific kitchen experiments, I’ve noticed that Monarch caterpillars PREFER Tropical milkweed. When offered a choice of Tropical milkweed, Swamp Milkweed or Antelope horns, Monarch caterpillars inevitably choose Tropical milkweed.
Studies show that the toxins in Tropical Milkweed inoculate Monarch moms and their young.
While it can be challenging to find Tropical milkweed in the Fall when Monarchs are moving through Texas, it’s easy to cut back your spring plants to encourage new growth for migrating visitors. My butterfly breeder friend Connie Hodson, of Flutterby Gardens in Manatee, Florida, says you can cut any six-inch stalk of Tropical milkweed in a potting soil and vermiculite mix, and have new plants in no time. You can also order seeds or harvest them yourself from fellow gardeners.
NOTE: If you choose to plant Tropical milkweed, best practice suggests slashing it to the ground in late fall or early winter. It will push out new shoots as the weather warms. This will discourage overwintering of organisms possibly harmful to Monarchs.