Sweet Alyssum in Zone 10a & 10b
Lobularia maritima
When to plant sweet alyssum in zone 10b
Zones 10a and 10b share the same average frost dates in our data, so this page covers both.
Method: Start indoors: Start indoors from seed, then transplant outside. In your zone, Sweet Alyssum needs a head start on the heat that direct-sowing elsewhere doesn't require.
| Window | Fall window |
|---|---|
| Start indoors | Aug–Jan |
| Direct sow / transplant outside | Oct–Mar |
| Estimated bloom | Nov 10–May 10 '27 (~40 days after transplanting) |
Spacing: 3 per square foot (square-foot-gardening spacing). Mature height: 3-10 in.
Zone 10b dates sourced from growinginthegarden.com.
Sweet alyssum is one of the better-documented companion flowers in this whole list, backed by actual published field research on why it's planted alongside crops like lettuce and broccoli. It stays low, a 4- to 8-inch spreading mat, and disappears under dense clusters of tiny, four-petaled white or purple flowers.
How sweet alyssum fits zone 10's season
Zone 10b's frost-free window runs about 324 days, from January 30 to December 20. Sweet Alyssum needs about 40 days from sowing to first harvest.
Good companions
- Broccoli: Sweet alyssum intercropping is documented to attract aphid-eating hoverflies, but the published research behind this (Brennan 2013) specifically tested lettuce, not broccoli — treat the broccoli extension as plausible but unconfirmed by that study.
- Lettuce: A published field study (Brennan 2013, Biological Control) found strip-intercropping lettuce with sweet alyssum reduces aphid pressure via hoverflies, whose larvae can eat up to 150 aphids a day — real, measured pest control, not folklore.
Where to buy sweet alyssum seeds
See why we recommend these suppliers →
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See it growing
Search YouTube for "growing sweet alyssum" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
← Back to the full zone 10b calendar · Full companion planting guide · Full plant profile · Plan your beds in the Garden Designer →
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Growing Sweet Alyssum in USDA zone 10b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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