Cleome (Spider Flower) in Zone 9a & 9b
Cleome hassleriana
Yes, cleome (spider flower) grows in zones 9a and 9b. Start seeds indoors Dec 28–Jan 4 and plant out Mar 1–Mar 8.
When to plant cleome (spider flower) in zone 9b
Zones 9a and 9b share the same average frost dates, so this page covers both.
Method: Either: Start indoors for an earlier harvest, or direct-sow outside for less fuss. Either works.
| Start indoors | Dec 28–Jan 4 |
|---|---|
| Direct sow / transplant outside | Mar 1–Mar 8 |
| Estimated bloom | May 15–May 22 (~75 days after planting) |
Spacing: 1 per square foot (square-foot-gardening spacing). Mature height: 1.5-6 ft.
Plant alongside it in zone 9b
These go outside within two weeks of cleome (spider flower) in zone 9b, so one planting day can cover them.
- NasturtiumFeb 22–Mar 1
- MarigoldFeb 22–Mar 1
- Angelonia (Summer Snapdragon)Mar 1–Mar 8
- Bee BalmMar 1–Mar 8
- Black-Eyed Susan VineMar 1–Mar 8
- Chrysanthemum (Garden Mum)Mar 1–Mar 8
Cleome, also called spider flower, is one of the taller plants on this site, anywhere from 1.5 to 6 feet depending on the cultivar, and it earns that height by being a serious draw for hummingbirds, bees, butterflies, and predatory insects that help keep pest populations down elsewhere in the garden. The classic species form does have a downside worth knowing up front: sticky sap, a noticeable odor, and stems armed with small spines.
How cleome (spider flower) fits zone 9's season
Zone 9b's frost-free window runs about 293 days, from February 15 to December 5. Cleome (spider flower) needs about 75 days from sowing to first bloom.
Cleome (Spider Flower) 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 |
|---|---|---|---|
| 2a & 2b | Apr 1–Apr 8 | Jun 3–Jun 10 | Aug 17–Aug 24 |
| 3a & 3b | Apr 11–Apr 18 | Jun 13–Jun 20 | Aug 27–Sep 3 |
| 4a & 4b | Mar 27–Apr 3 | May 29–Jun 5 | Aug 12–Aug 19 |
| 5a & 5b | Mar 22–Mar 29 | May 24–May 31 | Aug 7–Aug 14 |
| 6a & 6b | Mar 7–Mar 14 | May 9–May 16 | Jul 23–Jul 30 |
| 7a & 7b | Feb 20–Feb 27 | Apr 24–May 1 | Jul 8–Jul 15 |
| 8a & 8b | Feb 4–Feb 11 | Apr 8–Apr 15 | Jun 22–Jun 29 |
| 9a & 9b (your zone) | Dec 28–Jan 4 | Mar 1–Mar 8 | May 15–May 22 |
| 10a & 10b | Dec 12–Dec 19 | Feb 13–Feb 20 | Apr 29–May 6 |
| 11a & 11b | Nov 13–Nov 20 | Jan 15–Jan 22 | Mar 31–Apr 7 |
Bloom dates are about 75 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 cleome (spider flower).
Where to buy cleome seeds
True Leaf Market · Burpee · High Mowing Organic Seeds (each supplier's cleome seeds)
See why we recommend these suppliers →
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See it growing
Search YouTube for "growing cleome (spider flower)" 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 Cleome (Spider Flower) in USDA zone 9b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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