Story and Photos by Alan Pulley
Gomphocarpus physocarpus has several common names – balloon plant, swan plant, balloon cotton-bush, and others – however, it is most commonly referred to as hairy balls. The name will surely draw a snicker from those with a sense of humor.
Regardless of which name you prefer, hairy balls is actually a type of milkweed that is both interesting and beneficial to have in the garden. Once classified as Asclepias physocarpa, hairy balls is in the African milkweed family. It is a large plant that can reach over 6 feet tall, and in late summer, when covered with 2-inch chartreuse hairy seedpods, it is certain to draw attention. The cut branches last several weeks and add an unusual touch to any bouquet, dried arrangement, or wreath.
Hairy balls can be started in indoors four to six weeks before the last frost, or directly sown outdoors in spring. Keep the soil moist and barely cover the seed, as light aids in its germination. It thrives in full sun in dry to medium moist soil with good drainage. It also does well in large containers.
Hairy balls is an attractive milkweed and host plant for monarch butterflies. It certainly is a unique plant that deserves a place in the garden.
Quick Facts and Keys to Success
Common Name(s): Hairy balls, swan plant; balloon milkweed; balloon cotton-bush
Botanical Name: Gomphocarpus physocarpus (formally Asclepias physocarpa)
USDA Hardiness Zone(s): 8-10
Color: Small white flowers followed by chartreuse seedpods
Blooming Period: Mid-late summer through fall
Type: Deciduous shrub grown as annual
Mature Size: 6 feet tall, 3 feet wide
Exposure: Full sun
When to Plant: Spring, after danger of frost
Soil: Medium moist, well drained
Watering: Infrequently once established
When to Prune: Not necessary
When to Fertilize: Typically not necessary
In Your Landscape: Back of border mixed with other tall plants, such as sunflowers (Helianthus spp.); a butterfly garden, and/or cutting garden.