Giant Swan Plant Milkweed for Monarchs
Gomphocarpus physocarpus: Asclepias physocarpa is the former botanical name, Goose plant, Giant swan plant, Hairy balls, Family jewels, Oscar, Cotton-bush, Balloon plant milkweed
- 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 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
- Stem Cuttings
- Start seeds in water
- In annual zones, starting with plants is the best option to insure 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 amazing table centerpiece
- Use long cuttings to feed caterpillars indoors
- Last viable milkweed species before fall takes over
- Colder hardiness zones must start seeds indoors for hopes of a 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
- Use an 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
The most frequent visitor I’ve noticed up north is the blue mud dauber (black wasp). Recently, I’ve also noticed monarchs and hummingbirds sipping nectar from it. If you have noticed other pollinators on the goose plant, please leave a comment below.
nature note: Though the mud daubers look ominous, they have never shown aggression in our garden. They’re also frequent visitors to our swamp and tropical milkweed plants.
One more time: starting seeds indoors early will give you a huge jump on the season and is a must for northern gardeners. This milkweed species is a rare find in nurseries, so seeds are probably your only option in most regions.
Click here to Explore other Milkweed Options for your Butterfly Garden