Milkweed Seeds - Balloon


Unavailable for 2024

Gomphocarpus physocarpus

Previously classified as Asclepias physocarpa, but changed to reflect its tropical roots, this variety also has several common names like Swan plant, Balloon plant, Hairy Balls, and Family Jewels. Extremely popular in the cut flower industry for its unusual ball-shaped seed pods, and the flowers, though less showy than other milkweeds, are loved by pollinators. Summer blooming. Full Sun. Perennial in the South, but should be cut back in fall to encourage proper Monarch butterfly migration behavior. Non-native tropical milkweeds growing late in the year in the Southeastern US may encourage Monarchs to lay their eggs too far north, where the eggs will not survive the winter. 

SMALL FARM GROWN by Milkweed Meadows, Hendersonville, NC

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  • Planting Information
  • Growing Information


Average Seed / ozSeed / 100' RowAverage Yield / 100' RowDays to Harvest
Planting SeasonIdeal Soil TempSunFrost Tolerance
Fall65-80°FFull SunLightly Tolerant
Sowing MethodSeed DepthDirect Seed SpacingSeeds Per Packet
Direct Seed1/8"6-8"80
Mature SpacingDays to SproutProduction CycleSeed Viability
24-36"21-28Perennial2-3 years

Site Selection


This tropical milkweed is hardy in zones 8-10 and grown as an annual elsewhere. Prefers full sun and will thrive in dry to medium moisture soils.




Seeds can be started indoors 6-8 weeks before the last frost date. Sow seeds 1/8" deep and 6-8" apart. Optimal soil temperature for germination is 65-80˚F. Seeds will sprout in 10-28 days. Thin seedlings so that mature plants are 24-36" apart. Transplant outdoors once the danger of frost has passed.


*A note about tropical milkweeds i.e. Balloon Milkweed (Gomphocarpus physocarpus), and Bloodflower Milkweed (Asclepias curassavica)

There is some controversy over whether it is good practice to plant non-native milkweed. We at Sow True Seed believe that all food and habitat for pollinators is a good thing! However, if you are gardening in zones 8-10, where tropical milkweed can survive year round, please cut back these plants in early fall, before seed pods reach maturity. There is evidence that tropical milkweeds surviving late in the season in the Southern US discourage the proper southward migration of Monarch butterflies by providing egg-laying habitat too far north, when the butterflies should be headed for Mexico. Thank you for caring for our pollinators!