Love them or hate them, you cannot deny the beauty of intricately crafted milkweed blooms, often deliciously perfumed and beloved by butterflies. Some Asclepias are well known invasive weeds, many are course stalwart plants more suited to a wild prairie garden, and relatively few may gain admittance to a rock garden. The North American west holds a number of fascinating dwarf Asclepias species, most will be challenging to cultivate. Let me start with one of the most remarkable dwarf milkweeds, the rare Asclepias uncialis, or Dwarf Milkweed (to that common name it holds more than true). There are two subspecies; ssp. uncialis, and ssp. ruthiae.
...ssp. uncialis flower close-up
...ssp. ruthiae plant out of flower
I found the following document, Rare Plant Surveys on Fort Carson 2006-2007, Colorado State Univ., 70 pages, 5.5 MB PDF, with information on Asclepias uncialis ssp. uncialis with two good photographs. Since the large multi-megabyte PDF download might be too slow for some viewers, under the fair use provision I include two screen captures (above) from the document showing this rare and extraordinary minuscule plant, small enough for a trough if it could be cultivated. The coins give a good sense about how tiny the plant is.