Sweet Alyssum is an annual or perennial grown for its blooms, which open from spring through fall and return year after year. It's hardy across USDA zones 5 through 9, shrugs off deer and grows just as well in a container as in the ground. Its flowers are a real draw for honeybees, native bees, and butterflies.
Sweet Alyssum — the short answer
Sweet Alyssum: grown in zones 5–9, full sun, pH 6–7, about 55 days to maturity.
- USDA zones
- 5–9
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Soil pH
- 6–7
- Growable Ground Plant Database
- Sun
- Full Sun
- Growable Ground Plant Database
- Days to Maturity
- 55 days
- Growable Ground Plant Database
- Frost-kill temp (growing season)
- 25°F
- Growable Ground Plant Database
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — each tile names its own row's source, because per-field provenance varies.
Score Sweet Alyssum on your exact land.
Zone averages can't see the slope, soil, frost, and sun that decide whether sweet alyssum actually takes — and those shift from one yard to the next. Enter your address and we'll score sweet alyssum against your land's real conditions.
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What Sweet Alyssum is
Sweet Alyssum grows as an annual or perennial and reaches around 6 inches at maturity. It blooms from spring through fall. It's also deer-resistant and well suited to containers.
How to grow Sweet Alyssum
Sweet Alyssum grows in USDA zones 5 through 9. Sweet Alyssum does best in full sun — at least 6 hours of direct sun a day — and soil from pH 6 to 7, on well-drained ground. It needs around 600 growing degree days to mature and a growing season of at least 40 frost-free days, which is why climate matters as much as soil.
USDA Zones
5-9
USDA PHZM 2023
Soil pH
6 - 7
Growable Ground Plant Database
Sun
Full Sun
Growable Ground plant catalog
Drainage
well (dry spells)
Growable Ground plant catalog
Frost Kill Temperature
25°F
Where cold starts killing growing tissue. Not a winter-survival floor — a dormant perennial takes far colder, which its hardiness zone answers.
Growable Ground Plant Database
Days to Maturity
55 days
Growable Ground plant catalog
GDD Required
600+
Growing degree-days of accumulated warmth it needs to mature — humid summers reach this faster than cool coastal ones.
Growable Ground plant catalog
Mature Height
0.5 ft
Growable Ground plant catalog
Frost-Free Days
40+
The frost-free stretch it needs start to finish — short-season areas may need an indoor head start.
Growable Ground plant catalog
Start the season right
Plant sweet alyssum in full sun with at least 6 hours of direct sun. It grows in the cool halves of the year, so sow it in spring or late summer rather than waiting for midsummer heat.
Match the soil
Sweet Alyssum prefers pH 6 to 7 (Growable Ground Plant Database). A quick soil test from your local Extension lab tells you whether to add lime or sulfur to land in band.
Water steadily
Keep the root zone evenly moist through establishment. A 2–3 inch mulch layer holds moisture without waterlogging.
Harvest at its peak
Cut sweet alyssum blooms in the cool of the morning, just as they open, for the longest display.
Where Sweet Alyssum thrives
Sweet Alyssum is hardy across USDA zones 5 through 9. Zone is only the starting point, though: the soil pH, drainage, and frost dates on your specific land decide how well it actually does.
A USDA zone is a 10°F band of average annual extreme winter minimum, so zones 5–9 spans average winter lows from -20°F to 30°F (USDA PHZM 2023). Across the 50 states and DC, that band covers 25 outright and splits 25 more down the middle — and which side of that line your land sits on changes the answer.
Zones 5–9·Where Sweet Alyssum growsOpen map →
This map is derived from the USDA ARS / PRISM Plant Hardiness Zone Map (2023) and is not the official USDA Plant Hardiness Zone Map.
Where Sweet Alyssum stands, state by state
Sweet Alyssum is rated for zones 5–9 — a cold floor USDA puts at -20 to -10°F. Across the 50 states and DC, 25 sit fully inside that band, the line runs through 25 more, and 1 sits outside it — and inside every split state, the same line runs on at county grain.
Fully inside zones 5–9
25 states
3 of 25 shown
The line runs through
25 states
3 of 25 shown
Sweet Alyssum’s band covers part of each of these states — which side of the line your county sits on changes the answer, and each state page draws it.
Outside zones 5–9
1 state
- North Dakota · zones 3b-4b
Winter cold is the limit here — the same plant often works in a container that comes under cover. Each link is that state’s own growing hub.
State zone extents: USDA Plant Hardiness Zone Map (PHZM) 2023. A zone is a 10°F band of average annual extreme minimum temperature, so a state that splits the band contains the boundary — its own page draws the county line, and a parcel report resolves which side your land sits on.
What grows around Sweet Alyssum
Growing guides for sweet alyssum
In rotation planning, sweet alyssum counts as a Brassica — beds recover best when brassica crops don’t follow each other in the same spot year over year. (Growable Ground derivation — crop-rotation group from botanical family)
Related plants in annual flower
Good to know
Good news for pet owners — sweet alyssum isn't known to be toxic to dogs or cats. (Source: ASPCA.)
Sweet Alyssum is a standout pollinator plant — high value to bees and other pollinators. (Source: Xerces Society.)
Your land is one point inside Sweet Alyssum's range
This page resolves to the species. Your state page draws the county line, and a report reads the parcel — the soil pH, drainage, sun, and frost dates on your exact ground, which no species average can see.
See if Sweet Alyssum will thrive on your land
Zone averages are a start. Your exact soil pH, drainage, sun exposure, and frost dates shape whether sweet alyssum actually takes — we score it against the real conditions at your address.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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How we know this about Sweet Alyssum
The figures above are cited per row, not per site: the pH band names this plant’s own source column, the three temperature figures each carry their own, and days-to-maturity cites the publication that actually lists it. All of it comes from the Growable Ground Plant Database — a compilation over FAO ECOCROP, USDA PLANTS, and university Extension sources, published openly with per-field provenance.
Grounded inUSDA PLANTS Database•USDA PHZM•ASPCA
Frequently asked questions
Can I grow Sweet Alyssum in my zone?
Sweet Alyssum grows in USDA hardiness zones 5 through 9 (USDA PHZM 2023). Zone is one factor — soil pH, drainage, and frost dates on your specific parcel also shape whether it takes.
When should you plant Sweet Alyssum?
Sweet Alyssum is a cool-season crop, so it goes in during the cool halves of the year — early spring, and again in late summer for a fall planting — rather than at the height of summer heat. Your local frost dates set the exact window — a Growable Ground report reads them for your address.
How much sun does Sweet Alyssum need?
Sweet Alyssum needs full sun — a spot that catches at least 6 hours of direct summer sun a day. In more shade it still grows, but usually gives a smaller, later crop. The catch is that a yard rarely gets even light everywhere — a fence, the house, or one tall tree can quietly take those hours. A Growable Ground report reads the real sun-hours across your land, canopy and buildings included, so you can pick the brightest bed before you plant.
What soil does Sweet Alyssum need?
Sweet Alyssum prefers soil pH 6 to 7, on well-drained ground (Growable Ground Plant Database). Your report scores your parcel's actual soil against that using USDA SSURGO data.
Does Sweet Alyssum attract pollinators?
Yes — sweet alyssum's flowers are a strong nectar and pollen source for honeybees, native bees, and butterflies. (Source: Xerces Society.)
Is Sweet Alyssum safe for pets?
Sweet Alyssum is not known to be toxic to dogs or cats based on available data. Always supervise pets around new plantings. (Source: ASPCA.)
Keep exploring Sweet Alyssum
Sweet Alyssum state by state
Every state sweet alyssum's zone reaches — 3 link straight to that state's sweet alyssum growing page; the rest open the state's full growing guide.