Post last updated: November 12th, 2019
Gomphocarpus physocarpus is the botanical name for a plant more commonly known as Balloon plant, Balloon Cotton bush, Bishop’s Balls, Elephant Balls, Family Jewels Tree, Goose Plant, Giant Swan Plant, Hairy Balls, Monkey Balls, and Oscar.
Cee, the Southern Rural Route’s butterfly lady, introduced the plant to me as Hairy Balls. Thus, it will always be Hairy Balls because I’m doing good to remember any name at all. Throw in a name change and I would be in serious trouble. She generously shared a couple of 2-inch plants for experimental growing in my garden.
Gomphocarpus physocarpus was formerly Asclepias physocarpa. I don’t know when it was reclassified. Confusion will abound going forward because there is always someone who didn’t get the memo on reclassification. For instance, the USDA plant database seems aware of the change but their charts still reflect the Asclepias classification.
It is a species of milkweed, a tropical/tender perennial (for Zones 8 through 11) that blooms in the late summer and early fall.
The plant resembles the common milkweed but it can grow to 5 or 6 feet, the leaves are a lighter shade of green, and not as wide or long as common milkweed leaves.
It is both a host and nectar plant for the Monarch butterfly.
Typical of milkweed plants, aphids can be a problem.
My plant became very unattractive – a single, woody stalk curling out towards the sun. I pulled it out and tossed it after collecting seeds. Research indicates that I could have pruned it in the late spring to make it bushier. Late spring may work for northern climates but in the South, if you wait that long the plant will be four feet tall. Use your own judgment for your climate.
The seed pods are yellowish-green round balls that grow to about 2-1/2 inches in overall length. They are covered with soft whisker-like hairs spaced 1/4-inch from each other.
Collect seeds in the fall. Allow the pod to turn a rosy-tan color for seed maturity. After the seed pod cracks, break it open and strip the seeds from the white “silks.” The seeds should be brown/black and dry looking. Dry completely before storing.
Hairy Balls is normally grown from seeds wind-sown by the plant (bag the seeds to avoid). In Southern climates it can be fall-sown. In northern climates, start seeds indoors in the early spring several weeks before the last frost. The seed does not need to be cold stratified.
Do not cover the seed when sowing and keep the soil moist and in bright light to aid germination (15 to 30 days). Being a tropical milkweed, it will germinate best in warm temperatures (68-80F).
It is considered an invasive in the tropics, subtropics, semi-arid and hyper-arid climates. It grows freely in Hawaii and Africa.
Poisonous if ingested.