Balloon Plant for Monarch Caterpillars
Gomphocarpus physocarpus: Asclepias physocarpa is the old 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
- Start seeds indoors 2 months before final frost
- Sow seeds directly after final frost (not recommended below zone USDA zone 8)
- Soak seeds in warm water 24 hours before planting
- Stem Cuttings in warm water
- Leaf cuttings
- In annual zones, balloon plants are better if you can find them locally or online
- Fastest growing annual milkweed
- Can sustain lots of monarch caterpillars late season
- 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
- Flowers aren’t super showy, but still pretty
- Up north, only pollinated by wasps (and one red admiral!)
- Potentially difficult to overwinter? (I brought one in balloon plant that died. Perhaps it wasn’t getting enough light?)
WINTER 2014 UPDATE: I’m currently overwintering 4 balloon plants and they are all thriving under CFL light bulbs
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
Not much to report up north. The only pollinator I’ve noticed visiting this milkweed on a regular basis is the blue mud dauber (black wasp). 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. 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