Swan Milkweed for Monarch Caterpillars
Gomphocarpus fruticosus: Asclepias fruticosa is the old botanical name, Narrowleaf cotton bush, Swan bush, Swan milkweed
- Perennial for USDA hardiness zone 10a and up 10a-11 (lows to -1.1 °C or 30 °F)
- Fast growing annual for colder zones
- Full sun to part shade
- Height: 4 to 6 feet (compact shrub compared to balloon plant milkweed)
- Spacing: 3 to 4 ft
- Flowers: White
- Blooms mid to late summer
- Start seeds indoors 2 months before final frost
- Cool moist stratification? put containers in a 3-season porch two months before final frost to experience extreme temperature fluctuations (use same containers as cold moist stratification)
- 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
- In annual zones, buying plants is recommended if you can find them locally or online
- In annual zones, overwintering plants indoors is also an option
- Seed propagation directly in water
- Fast growing annual milkweed
- Can sustain lots of late season monarch caterpillars
- Year one– this gets more eggs in our northern garden than balloon plant (G. physocarpus)
- Stems with unique seed pods can be used for a table centerpiece
- Use long cuttings to feed caterpillars indoors
- Lasts until after first hard freeze
- Annual hardiness zones must start seeds indoors for hopes of harvesting mature seed
- Flowers aren’t very showy, but still pretty
- Should be cut back in perennial regions like tropical milkweed to avoid spreading OE parasites.
- Still testing to see whether this is a nectar source for monarchs or other pollinators. Try native species or tropical milkweed if you’re looking for a sure thing.
Swan 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!
- Can hybridize with Gomphocarpus physocarpus- choose one if you don’t want this to happen
- Cut- 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 plain tiger butterfly (Danaus chrysippus) uses swan bush as a host and nectar plant in regions of Africa, Asia, and Australia. I’ll report on North American visitors as they are seen or reported by others. Please comment below if you know of any North American pollinators that frequent this milkweed variety.
One more time: starting seeds indoors early or overwintering plants 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 best option to get started in most regions.
Click here to Explore other Milkweed Options for your Butterfly Garden