Sweet William Dianthus barbatus
Sweet William (Dianthus barbatus) is a biennial flowering plant in the Caryophyllaceae family, native to Southern Europe, from the Pyrenees to the Balkans. It grows 30–60 cm (12–24 in) tall and 20–35 cm (8–14 in) wide, wants full sun and moderate water, and is hardy to about -34 °C (-29 °F). Space plants about 25 cm (10 in) apart.
Plan Sweet William in your garden →
Free. Draw your beds, then watch it grow through the year in 2D and 3D.
Sweet William at a glance
| Type | Biennial flowering plant |
|---|---|
| Family | Caryophyllaceae |
| Mature height | 30–60 cm (12–24 in) |
| Mature spread | 20–35 cm (8–14 in) |
| Spacing | 25 cm (10 in) centre to centre |
| Sun | Full sun, at least 6 h of direct sun a day |
| Water | Moderate; drought tolerance low, waterlogging tolerance none |
| Soil pH | 6–7.5 |
| Cold hardiness | About -34 °C (-29 °F) once established (roughly USDA zone 4) |
| Heat stress | Likely above about 30 °C (86 °F) |
| Flowering | about 47–57 weeks after planting, for 4–6 weeks |
| Wind tolerance | Low |
| Pollinator value | High |
| Edible | Not grown as food |
| Native to | Southern Europe, from the Pyrenees to the Balkans |
| Common in gardens of | 🇬🇧 United Kingdom, 🇩🇪 Germany, 🇷🇺 Russia |
Is Sweet William toxic?
- People: mildly toxic
- Cats: mildly toxic
- Dogs: mildly toxic
- Parts: all parts, flowers
ASPCA lists Dianthus (sweet William) as mildly toxic to cats and dogs, causing mild vomiting, diarrhoea and skin irritation.
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with Sweet William
No well-documented helpful pairing. Group it with plants that like full sun and moderate water.
See Sweet William in a botanical garden
It grows in this sample garden, which you can walk through in 3D:
- Monet’s gardens at Giverny (70 plants)
Questions about Sweet William
- How far apart should I plant Sweet William?
- About 25 cm (10 in) apart, centre to centre. A mature plant spreads 20–35 cm (8–14 in).
- Does Sweet William need full sun?
- Full sun: at least 6 hours of direct sun a day.
- How much water does Sweet William need?
- Moderate water. Drought tolerance is low and waterlogging tolerance none.
- How cold-hardy is Sweet William?
- It tolerates about -34 °C (-29 °F) once established, roughly USDA zone 4. As a biennial it is usually planted out after the last frost and flowers in its second year.
- When does Sweet William flower?
- About 47–57 weeks after planting, for 4–6 weeks.
- Is Sweet William poisonous to cats and dogs?
- For cats it is mildly toxic; for dogs mildly toxic; for people mildly toxic. ASPCA lists Dianthus (sweet William) as mildly toxic to cats and dogs, causing mild vomiting, diarrhoea and skin irritation.
- What grows well with Sweet William?
- There is no well-documented companion pairing for Sweet William. Group it with plants that like the same sun (full sun) and water (moderate).
Sources and evidence
Evidence grade B (B: extension service or peer-reviewed).
- RHS Plant Finder, Royal Horticultural Society
- Missouri Botanical Garden Plant Finder, Missouri Botanical Garden
- ASPCA Toxic and Non-Toxic Plant List, ASPCA
Notes and assumptions
- Typical garden-form values; cultivars and local conditions differ.
- Grown as a biennial (or short-lived perennial); sown in early summer, flowers the following May to July; self-seeds.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
Related plants
- Carnation Dianthus caryophyllus
- China pink Dianthus chinensis
- Snow-in-summer Cerastium tomentosum
- Moss campion Silene acaulis
- Soapwort (bouncing bet) Saponaria officinalis
- Rock soapwort Saponaria ocymoides
- Creeping baby’s breath Gypsophila repens
- Maiden pink Dianthus deltoides