Gomphocarpus physocarpus: Plant of the Month January 2020
I don’t know about you, but I love having plants that are actually *doing* something for as long as possible (whether growing, flowering, or making fruit or seeds). One such plant is “balloon plant”, known botanically as Gomphocarpus physocarpus (formerly Asclepias physocarpus). This very close relative of the milkweed is exactly such a plant. It grows quickly and easily from seed sown in spring and begins flowering just a few months after that (I start seeds indoors in March to plant outside in May). The flowers are very milkweed-appearing with white petals and light purple centers, formed in pendulous clusters. The flowers, however, aren’t the appeal of this fun perennial plant (hardy to 15 degrees Fahrenheit). The real attraction are the fun, softly bristled, inflated seed pods that are formed in late summer and autumn (hence the common name). The pods make interesting additions to flower arrangements and are quite in vogue these days. Like milkweeds, the pods of balloon plant eventually turn brown and split open to release tufted seeds that float away on the wind.
Balloon plants are semi-shrubby and easily reach 5-6 feet, even in their first summer from seed. Give them full sun and fairly regular water and you’ll have success. Trim older plants back in mid-spring to keep them nice and bushy. Large specimens will attract monarch caterpillars that will feed on the leaves and eventually turn into butterflies. Below are some photos from our garden showing the flowers, fruit, and seeds. If you want to give yourself a laugh you can search online for the PG-rated common name for this fun plant, or just ask me the next time you see me.
Happy gardening! Grant (firstname.lastname@example.org)