China Aster in Zone 3a & 3b
Callistephus chinensis
Yes, China aster grows in zones 3a and 3b. Start seeds indoors Apr 11–Apr 18 and plant out Jun 6–Jun 13.
When to plant China aster in zone 3b
Zones 3a and 3b 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 | Apr 11–Apr 18 |
|---|---|
| Direct sow / transplant outside | Jun 6–Jun 13 |
| Estimated bloom | Sep 4–Sep 11 (~90 days after transplanting) |
Spacing: 4 per square foot (square-foot-gardening spacing). Mature height: 1.5-2.5 ft.
Plant alongside it in zone 3b
These go outside within two weeks of China aster in zone 3b, so one planting day can cover them.
- NasturtiumJun 6–Jun 13
- MarigoldJun 6–Jun 13
- Ageratum (Flossflower)Jun 6–Jun 13
- Annual Geranium (Pelargonium)Jun 6–Jun 13
- Butterfly Weed (Asclepias)Jun 6–Jun 13
- Campanula (Bellflower)Jun 6–Jun 13
China aster is not related to the perennial garden asters despite the common name; it's a true annual grown from seed each year for its full, peony-like cut-flower blooms.
How China aster fits zone 3's season
Zone 3b's frost-free window runs about 98 days, from May 30 to September 5. China aster needs about 90 days from transplant to first bloom.
China Aster planting windows in every zone
Zone 3b is highlighted. Useful for comparing against a neighbouring zone, or for a garden somewhere else.
| Zone | Start indoors | Sow or plant out | Bloom |
|---|---|---|---|
| 2a & 2b | Apr 1–Apr 8 | May 27–Jun 3 | Aug 25–Sep 1 |
| 3a & 3b (your zone) | Apr 11–Apr 18 | Jun 6–Jun 13 | Sep 4–Sep 11 |
| 4a & 4b | Mar 27–Apr 3 | May 22–May 29 | Aug 20–Aug 27 |
| 5a & 5b | Mar 22–Mar 29 | May 17–May 24 | Aug 15–Aug 22 |
| 6a & 6b | Mar 7–Mar 14 | May 2–May 9 | Jul 31–Aug 7 |
| 7a & 7b | Feb 20–Feb 27 | Apr 17–Apr 24 | Jul 16–Jul 23 |
| 8a & 8b | Feb 4–Feb 11 | Apr 1–Apr 8 | Jun 30–Jul 7 |
| 9a & 9b | Dec 28–Jan 4 | Feb 22–Mar 1 | May 23–May 30 |
| 10a & 10b | Dec 12–Dec 19 | Feb 6–Feb 13 | May 7–May 14 |
| 11a & 11b | Nov 13–Nov 20 | Jan 8–Jan 15 | Apr 8–Apr 15 |
Bloom dates are about 90 days after the sow or plant-out date, not after starting seeds indoors.
Zone 2 sows before zone 3 here, which looks wrong and is not. USDA zones rank winter cold, not season length, and zone 2 is mostly interior Alaska, where hard winters come with warm summers. More on what a zone measures.
Good companions
No well-established companions for China aster.
Where to buy China aster seeds
None of the seed suppliers we list carries China aster 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 China aster" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
← Back to the full zone 3b calendar · Plan your beds in the Garden Designer →
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Growing China Aster in USDA zone 3b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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