Butterfly Weed (Asclepias) in Zone 9a & 9b
Asclepias tuberosa
Yes, butterfly weed (asclepias) grows in zones 9a and 9b. Start seeds indoors Dec 21–Dec 28 and plant out Feb 22–Mar 1.
When to plant butterfly weed (asclepias) in zone 9b
Zones 9a and 9b share the same average frost dates, so this page covers both.
Method: Start indoors: Start indoors from seed, then transplant outside. It needs a head start most zones can't give it by direct-sowing alone.
| Start indoors | Dec 21–Dec 28 |
|---|---|
| Direct sow / transplant outside | Feb 22–Mar 1 |
| Estimated bloom | About a year after planting |
Spacing: 1 per square foot (square-foot-gardening spacing). Mature height: 1.5-3 ft.
Plant alongside it in zone 9b
These go outside within two weeks of butterfly weed (asclepias) in zone 9b, so one planting day can cover them.
- NasturtiumFeb 22–Mar 1
- MarigoldFeb 22–Mar 1
- Ageratum (Flossflower)Feb 22–Mar 1
- AmaryllisFeb 22–Mar 1
- Annual Geranium (Pelargonium)Feb 22–Mar 1
- Calla LilyFeb 22–Mar 1
Butterfly weed is a native perennial wildflower grown as much for feeding monarch butterfly caterpillars, one of the milkweeds they depend on, as for its own clusters of bright orange flowers.
How butterfly weed (asclepias) fits zone 9's season
Zone 9b's frost-free window runs about 293 days, from February 15 to December 5. Butterfly weed (asclepias) takes about a year from planting to first bloom, so it spans more than one growing season.
Butterfly Weed (Asclepias) planting windows in every zone
Zone 9b is highlighted. Useful for comparing against a neighbouring zone, or for a garden somewhere else.
| Zone | Start indoors | Sow or plant out | Bloom |
|---|---|---|---|
| 3a & 3b | Apr 4–Apr 11 | Jun 6–Jun 13 | About a year after planting |
| 4a & 4b | Mar 20–Mar 27 | May 22–May 29 | About a year after planting |
| 5a & 5b | Mar 15–Mar 22 | May 17–May 24 | About a year after planting |
| 6a & 6b | Feb 28–Mar 7 | May 2–May 9 | About a year after planting |
| 7a & 7b | Feb 13–Feb 20 | Apr 17–Apr 24 | About a year after planting |
| 8a & 8b | Jan 28–Feb 4 | Apr 1–Apr 8 | About a year after planting |
| 9a & 9b (your zone) | Dec 21–Dec 28 | Feb 22–Mar 1 | About a year after planting |
Good companions
No well-established companions for butterfly weed (asclepias).
Where to buy butterfly weed seeds
None of the seed suppliers we list carries butterfly weed seeds right now. A local garden center or a specialty seed house is the place to look.
See why we recommend these suppliers →
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See it growing
Search YouTube for "growing butterfly weed (asclepias)" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
← Back to the full zone 9b calendar · Plan your beds in the Garden Designer →
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Growing Butterfly Weed (Asclepias) in USDA zone 9b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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