China Aster in Zone 5a & 5b
Callistephus chinensis
Yes, China aster grows in zones 5a and 5b. Start seeds indoors Mar 22–Mar 29 and plant out May 17–May 24.
When to plant China aster in zone 5b
Zones 5a and 5b 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 | Mar 22–Mar 29 |
|---|---|
| Direct sow / transplant outside | May 17–May 24 |
| Estimated bloom | Aug 15–Aug 22 (~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 5b
These go outside within two weeks of China aster in zone 5b, so one planting day can cover them.
- NasturtiumMay 17–May 24
- MarigoldMay 17–May 24
- Ageratum (Flossflower)May 17–May 24
- Annual Geranium (Pelargonium)May 17–May 24
- Butterfly Weed (Asclepias)May 17–May 24
- Campanula (Bellflower)May 17–May 24
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 5's season
Zone 5b's frost-free window runs about 148 days, from May 10 to October 5. China aster needs about 90 days from transplant to first bloom.
China Aster planting windows in every zone
Zone 5b 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 | 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 (your zone) | 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 5b calendar · Plan your beds in the Garden Designer →
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Growing China Aster in USDA zone 5b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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