Sweet William is a perennial grown for its red blooms, which open in summer and return year after year. It's hardy across USDA zones 3 through 9, shrugs off deer and grows just as well in a container as in the ground. Its summer flowers are a moderate draw for butterflies and moths.
Zones
3-9
pH Range
6.5-7.5
Sun
Full Sun
Days to Maturity
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Score Sweet William on your exact land.
Zone averages can't see the slope, soil, frost, and sun that decide whether sweet william actually takes — and those shift from one yard to the next. Enter your address and we'll score sweet william against your land's real conditions.
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What Sweet William is
Sweet William grows as a perennial and reaches around a foot and a half at maturity. It blooms red in summer. It's also deer-resistant and well suited to containers.
How to grow Sweet William
Sweet William grows in USDA zones 3 through 9. Sweet William does best in full sun — at least 6 hours of direct sun a day — and soil from pH 6.5 to 7.5, on well-drained ground.
USDA Zones
3-9
USDA PHZM 2023
Soil pH
6.5 - 7.5
USDA PLANTS Database
Sun
Full Sun
Growable Ground plant catalog
Drainage
well (dry spells)
Growable Ground plant catalog
Mature Height
1.5 ft
Growable Ground plant catalog
Start the season right
Plant sweet william 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 William prefers pH 6.5 to 7.5 (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 william blooms in the cool of the morning, just as they open, for the longest display.
Good to know
Good news for pet owners — sweet william isn't known to be toxic to dogs or cats. (Source: ASPCA.)
Sweet William offers moderate value to bees and other pollinators. (Source: Pollinator Partnership.)
Where Sweet William thrives
Sweet William is hardy across USDA zones 3 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.
Zones 3–9·Where Sweet William growsOpen map →
On USDA hardiness-zone overlap, Sweet William can grow in these states:
See if Sweet William will thrive on your land
Zone averages are a start. Your exact soil pH, drainage, sun exposure, and frost dates shape whether sweet william actually takes — we score it against the real conditions at your address.
Three things about your exact spot that zone averages miss:
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Frequently Asked Questions
Can I grow Sweet William in my zone?
Sweet William grows in USDA hardiness zones 3 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 William?
Sweet William 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 William need?
Sweet William 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 William need?
Sweet William prefers soil pH 6.5 to 7.5, on well-drained ground (Growable Ground Plant Database). Your report scores your parcel's actual soil against that using USDA SSURGO data.
Does Sweet William attract pollinators?
Yes — sweet william's flowers are a solid nectar source for butterflies and moths. (Source: Pollinator Partnership.)
Is Sweet William safe for pets?
Sweet William is not known to be toxic to dogs or cats based on available data. Always supervise pets around new plantings. (Source: ASPCA.)