Sweetwilliam (Dianthus barbatus)

How much light does a Sweetwilliam need?

Full sun outdoors suits sweet william best, with at least six hours of direct sunlight a day. It also tolerates part shade. Full sun is the light level listed as its preference, while part shade is the other condition it tolerates. This species is classed as a shrub. Its flowers appear in pink, purple, red, white, or multicolor combinations.

• Light: Full sun and part shade (full sun preferred)¹

Best soil for a Sweetwilliam

Sweet william needs soil with good drainage that also stays moist. A soil pH between 6 and 8, a near-neutral range, suits it well. It grows at a medium rate, and its maintenance need is rated medium. At maturity, it typically reaches 1 to 2 ft (0.3 to 0.6 m) tall and 6 in to 1 ft (0.15 to 0.3 m) wide.

• Soil drainage: Well drained and moist¹
• Soil pH: pH 6–8¹

Hardiness and temperature

USDA zones 3a through 9b cover the outdoor hardiness range for sweet william. That span runs from the coldest zone, 3a, to the warmest, 9b. A gardener anywhere within that range can grow it outdoors year-round. Deer and rabbits are also reported to avoid this plant.

• Hardiness: Zones 3a–9b¹

How to plant a Sweetwilliam

Outdoors, sweet william is hardy in USDA zones 3a through 9b. Its native range includes Austria, Bulgaria, France, Hungary, Italy, Poland, Romania, Spain, Ukraine, and several neighboring countries across Europe and Asia. In the continental United States and in Alaska, it is recorded as introduced rather than native. Deer and rabbits are also reported to leave this plant alone.

• Hardiness: Zones 3a–9b¹

Winter care

Sweet william is hardy outdoors from USDA zone 3a to zone 9b. It needs soil with good drainage that also stays moist. It has a medium maintenance rating. Its growth rate is also rated medium. Its native range reaches from parts of Europe to Korea.

• Hardiness: Zones 3a–9b¹

How to propagate a Sweetwilliam

Sweet william can be propagated from seed or by division. Both of these methods are listed as the ways this source names for starting new sweet william plants. It is classed as a shrub. Its flowers come in pink, purple, red, white, or multicolor forms. This species also has a medium growth rate and a medium maintenance need.

• Propagation: Seed and division¹

Common problems

Sweet william can be bothered by slugs and snails, especially in shaded areas. Other pests recorded for it include Ditylenchus dipsaci, Liriomyza huidobrensis, Naupactus leucoloma, and Spodoptera ornithogalli. It is also susceptible to crown rot and rust, particularly in poorly drained soils. Other diseases recorded for it include Dickeya dianthicola, Erwinia chrysanthemi, Phialophora cinerescens, Phymatotrichopsis omnivora, and Candidatus Phytoplasma solani. Deer and rabbits are reported to avoid this plant.

• Common pests: ditylenchus dipsaci, liriomyza huidobrensis, naupactus leucoloma, spodoptera ornithogalli, slugs and snails^2,1
• Common diseases: candidatus phytoplasma solani, dickeya dianthicola, erwinia chrysanthemi, phialophora cinerescens, phymatotrichopsis omnivora, crown rot and rust^2,1

Questions and answers

Is sweet william toxic to cats and dogs?

Yes, sweet william is toxic to both cats and dogs. The poison characteristics listed for both are low toxicity if eaten and minor skin irritation.

What light does sweet william need outdoors?

Sweet william grows best outdoors in full sun, and it also tolerates part shade. It is hardy outdoors from USDA zone 3a to zone 9b.

How do you propagate sweet william?

You can propagate sweet william from seed or by division. Both methods are listed as the ways this source names for starting new plants of this species.