Here are two photos of "Asclepias viridis" or GREEN MILKWEED. This is what grows in most of Texas, next to the highways and in open fields. It is deep rhizome shoots that come up with the spring rains, as well as from seeds. As long as there is water, this milkweed is prevalent. It can be harvested, washed, sterilized and frozen in ziplock bags. Freezing viridis milkweed works better than freezing tropical milkweed.
You can help maintain butterfly habitats by recognizing these milkweeds, and then not mowing the field varieties that grow wild.