Sweet William plant profile
Dianthus barbatus
A biennial flower for full sun.
Last updated .
When to plant
When to plant Sweet William
Sweet William is a biennial or short-lived perennial usually grown from seed; it forms a leafy clump the first year and flowers in spring of the second. NCSU notes it thrives in sun or partial shade and tolerates heat and humidity, making it a dependable cottage-border and cutting-garden plant in cooler regions.
The calendar shows this cited seasonal window as an approximate band. It does not convert the season into frost-adjusted dates.
Open Sweet William in my garden calendarShows the source-backed planting season, not frost-adjusted dates.
Growing conditions
- Sun
- Full sun
- Soil pH
- 6 to 8
- Lifecycle
- Biennial
- Hardiness
- Zones 3a to 9bFind my hardiness zone
Common problems
Watch for these
Also watch for: crown rot, rust, snails.
Evidence trail
Evidence behind this profile
Original extension and institutional publications behind the planting, care, and safety facts on this page.
- Dianthus barbatus (Sweet William)
North Carolina Extension Gardener Plant Toolbox (NC State Extension). Supports general reference. Checked 2026-06-18.