Gomphocarpus physocarpus: Asclepias physocarpa is the former botanical name, Goose plant, Giant swan milkweed, Hairy balls, Family jewels, Oscar, Cotton-bush, Balloon plant
Perennial for USDA hardiness zone 8 and above (lows -12.2 °C or 10 °F)
Fast-growing annual for colder zones
Full sun to part shade
Height: 4 to 6 feet (can grow taller)
Spacing: 2 to 3 ft
Flowers: white with purple accents
Blooms mid to late summer
Not the same plant as its bushier brother swan milkweed
Start Seeds indoors 2 months before the final frost.
Sow seeds directly after final frost (not recommended below zone USDA zone 8)
Soak seeds in water 24 hours before planting, no cold stratification.
Start Seeds in water.
In annual zones, starting with plants is the best option to ensure plants have time to seed.
Fast-growing annual milkweed
Can sustain lots of munching monarch caterpillars late season
Nectar source for monarch butterflies
Long stems with pods make an amazing table centerpiece
Use long cuttings to feed caterpillars indoors
The last viable milkweed species before fall takes over
Colder hardiness zones must start seeds indoors for hopes of seed harvest, or overwinter indoors under CFL light bulbs
Flowers aren’t super showy, but still pretty
Fewer pollinators use this than native milkweeds
Goose Growing Tips:
Start seeds indoors 1-2 months before avg last frost
Seeds germinate in less than one week with heat and moisture
Description automatically generated oscillating clip fan on seedlings to strengthen the stems to simulate an outdoor breeze…a must for strong stems!
Grow this as a back border so it doesn’t shade your other butterfly plants
Cut I- you can cut them back late spring for bushier growth
Staking may be required if not cut back in perennial zones
Cut II- Is fall setting in before seeds are ready to harvest? Take stem cuttings with the largest pods (leave seed pods attached) and place them in water. This should give them the time they need to finish developing.
Don’t force open seed pods…they will start to open when they are ready.