Aquatic Milkweed

Aquatic Milkweed, Asclepias perennis, one of our native milkweeds, is a well-suited plant for Houston’s soggy gardens, as it is one plant that you cannot overwater. In most of its range it is known as an obligate hydrophyte, meaning it almost always occurs in wetlands. It is naturally found in wet soil, floodplains, marshes, ditches, and swamps. This is good news for gardeners, as many native milkweeds prefer to be high and dry, which is just not always possible here in Houston!

Milkweeds are amazing plants for so many reasons. Most notably, they are the host for the ever-popular monarch butterfly, and necessary for their reproduction and development. Milkweeds are, as the name implies, weeds, so they used to be abundant in fields and meadows, and along roadsides. Over time, farming, mowing, urbanization, and pesticides have drastically reduced milkweed populations, which in turn, have drastically reduced monarch populations. Because people love monarchs so much, many well-meaning gardeners have been trying to help replenish milkweeds by planting mostly non-native species, such as tropical milkweed (Ascelpias currasavica). While any help is appreciated, native milkweeds are always the best choice, because native pollinators and wildlife get the most benefits from native plants. The biggest challenge to gardeners is that native milkweeds are often fussy, hard to grow, and hard to find. Enter aquatic milkweed! This is a very hearty and dare I say, easy species to grow, so if you can find it, plant it!

Native milkweeds are not only valuable to the monarch, they also attract a large number of native bees, another important group of pollinators that is in peril. In fact, their nectar is loved by all bees, butterflies, and hummingbirds. Milkweeds also attract a lot of herbivorous insects. Although their sap is toxic, several species of insects have evolved an immunity and the ability to use the toxins as protection from predators. These insects all use aposematic, or warning coloration to advertise this toxicity to would-be predators. Combinations of orange, black, white, and yellow are a warning of their bitter, vomit-inducing taste! All of the life that a milkweed supports is commonly referred to as the milkweed village, and it’s just one thing that makes this an incredibly important plant!

(By guest contributor: Dany Millikin, Director of Education, Houston Botanic Garden)