Butterfly weed
Asclepias are commonly known as milkweeds and the sap from their fleshy stems may be a skin irritant so wear gloves when handling or propagating these plants.
A. tuberos has flowers which are especially attractive to bees and it is therefore very suitable for growing both in a border or in a wild flower garden designed with pollinators in mind. It grows to about 3ft in maturity and has stout stems which are unbranched and lance shaped mid-green leaves of about 4in in length. The flowers are orange or yellowish orange in terminal clusters about 2in across. These appear from July to September.
Asclepias incarnata ‘Ice Ballet’ (Swamp Milkweed) has pure white flowers although the species, A. incarnata, has pinkish-purple flowers. This is also a thick stemmed perennial from the USA growing to around 3½ - 4 feet tall and just as hardy as A. tuberosa. The flowers are produced from above the upper leaf axils in terminal clusters from midsummer until autumn. After the flowers erect fruits of up to 3 inches long are produced in the autumn.
Growing the two species together in a border creates an excellent late summer colour contrast.
These are fully hardy perennial plants which prefer a fertile well drained soil in full sun. At Burncoose we have grown these plants successfully in the conservatory for many years. They make excellent greenhouse plants when grown in pots in a loamy compost in full light but with some shading on the glass. The plants produce long fruits which can be collected and sown in pots in the spring. They can also be propagated by root cuttings or by division in the spring.