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Planting Native Milkweed is the Right Thing to do
A number of years ago I became interested in monarch butterflies after visiting their wintering grounds in Mexico. Like most monarch enthusiasts at that time, I went to a local nursery and purchased the only milkweed available, tropical milkweed (Asclepias curassavica). Over the years since then I have learned that there are a number of problems associated with tropical milkweed that are detrimental to the health of monarchs. Because of this I have removed this milkweed from my garden, and I recommend that you do the same. Unfortunately, most nurseries and box stores still only sell tropical milkweed because it is easy to propagate and grows year-round. Luckily groups such as Native Plant Society of Texas, Master Gardeners and Audubon Society are aware of the problems that accompany tropical milkweed and have begun to feature native milkweeds at their plant sales.
There are 200 species of milkweed found around the world. Approximately 30 of those are found in Texas. The Houston area is home to 5-7 native milkweeds (experts don’t always agree).
Asclepias perennis, aquatic milkweed, is a milkweed that prefers moist soil and will even survive periodic flooding. It is a Houston native with white flowers that is found on low, swampy ground. It grows in full sun, if it is watered adequately, to part shade. I have found perennis easy to grow from seed. Perennis does not have a taproot which makes it suitable for containers. This is the one native milkweed that I have that does not go dormant during a normal Houston winter.
There are several native milkweeds that enjoy sunny, dry areas. Asclepias oenotheroides, zizotes milkweed, and Asclepias viridis, green milkweed, are both Houston natives with taproots that make them drought tolerant once established. They both have pale green flowers. Zizotes is easy to grow while viridis is more challenging to get established. Once established viridis is a wonderful milkweed to have. Both of these milkweeds go dormant in the winter. Viridis also goes dormant during the hottest and driest part of Houston summers, but it has a growth spurt and even flowers again in the fall.
Asclepias tuberosa, butterfly milkweed, is a Texas native that grows in poor soil. It prefers full sun and has a taproot that makes it drought tolerant. This milkweed may take a couple of years to get established but with its bright reddish orange flowers it is a showstopper. Tuberosa does not have the milky sap that other milkweeds have, but monarchs still use it as a larval food. It also goes dormant in the winter and puts on new growth late in the spring.
Asclepias verticillata, whorled milkweed, has a reputation for being easy to grow. I have less experience with it than with some other milkweeds. It has very narrow leaves and stems that can blend in with grass and be overlooked when the white flowers are not in bloom. It prefers full sun but will tolerate part shade. Verticillata is drought resistant and needs well drained soil. It can form colonies from underground rhizomes but is not considered invasive. This is a late blooming milkweed and is the last of the natives to go dormant for the winter.
I hope you have found something among the native milkweeds that looks interesting and that you are ready to try. Look for them at the spring sales of the organizations I mentioned earlier or try your hand at growing your own from seeds.