Dianthus barbatus, sweet William
1 / 6
Perennials

Dianthus barbatus

sweet William

CaryophyllaceaeEurope, Asia

At a Glance

TypeBiennial
HabitUpright
FoliageEvergreen
Height12–24 inches (30–60 cm)
Width9–12 inches (23–30 cm)
Maturity1 years

Growing Zones

USDA Hardiness Zones

3 - 9
Zone 3
Zone 4
Zone 5
Zone 6
Zone 7
Zone 8
Zone 9
These zones indicate the coldest temperatures this plant can typically survive.
Frost Tolerancehardy

Key Features

Attracts Pollinators
Attracts Butterflies
Fragrant (light)
Container Friendly
Maintenancemoderate

Overview

Dianthus barbatus, commonly called sweet William, is a herbaceous biennial or short-lived perennial in the family Caryophyllaceae, native to southern Europe and parts of Asia, from the Pyrenees east through the Balkans to Russia. Plants grow 12–24 inches (30–60 cm) tall with opposite, lance-shaped bright green leaves joined at swollen nodes. In late spring to early summer, dense, flattened clusters (corymbs) of up to 30 flowers, each 0.8–1.2 inches (2–3 cm) across with five fringed-edged petals, are produced at stem tips in white, pink, red, salmon, purple, and bicolored or eyed combinations. Wild plants produce red flowers with a white basal zone; the species has been cultivated since at least the sixteenth century and a vast range of cultivars exists. The flowers carry a light, spicy-sweet clove fragrance. Grown as a biennial in most Pacific Northwest gardens — sown in summer, overwintered as a rosette, and flowering the following year — though perennial strains exist. Mildly toxic; may cause skin irritation in sensitive individuals and mild gastrointestinal upset if ingested in large quantities by pets.

Native Range

Native to southern Europe, from the Pyrenees through France, Italy, the Balkans, and east through southeastern Europe to Russia and parts of western Asia. The species grows in open meadows, rocky slopes, and scrub at low to moderate elevations. It has been widely cultivated since the sixteenth century and is naturalized in many temperate regions, including parts of North America.

Suggested Uses

Sweet William is a classic cottage garden biennial for mixed borders, cutting gardens, and spring bedding schemes. The dense flower clusters in a wide range of colors and bicolored combinations create bold splashes of late-spring color. Plant in successive waves — first- and second-year plants together — for continuous display. Combines well with roses, foxgloves, and alliums in late-spring borders. The lightly fragrant flowers are attractive to butterflies and bees and make excellent cut flowers with moderate vase life.

How to Identify

Sweet William is identified by opposite, lance-shaped bright green leaves with bases that clasp the stem at swollen nodes, giving a characteristic jointed appearance. Flower stems are erect, bearing dense, flattened-topped clusters of fringed five-petaled flowers in white, pink, red, or bicolored combinations, often with a contrasting basal eye zone of a different color. The spicy-clove fragrance is a further identifying feature. Plants overwinter as low rosettes of flat, broad leaves.

Appearance

Size & Dimensions

Height1' - 2'
Width/Spread9" - 1'

Reaches mature size in approximately 1 years

Colors

Flower Colors

white
pink
red
salmon
purple

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~6 weeks
J
F
M
A
M
J
J
A
S
O
N
D
SpringSummer
Sweet William blooms in late spring to early summer, typically May through July in Pacific Northwest gardens. The flattened flower clusters open over four to six weeks, with individual flowers persisting for one to two weeks. Plants grown as biennials flower in their second year; if stems are cut back after the first flowering flush, plants may produce a smaller secondary bloom in late summer. Removing spent flower heads before seed set may extend the blooming period.

Detailed Descriptions

Flower Description

White, pink, red, salmon, purple, or bicolored

Foliage Description

Bright to medium green, lance-shaped

Growing Conditions

Sun Requirements

Full Sun
Partial Shade
Requires 4-8 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.5 - 7.5(Neutral)
357912
Soil Types
loamsandchalk
Drainage
well drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

1–2 years

Care & Maintenance

Care Guide

Treat sweet William as a biennial for best results: sow seeds indoors in June–July or directly in the garden in late summer, overwinter transplants in the ground, and flowers will appear the following May through July. Plant in full sun to part sun in fertile, well-drained, neutral to slightly alkaline soil; poor drainage or acidic soil reduces vigor. Space plants 9–12 inches (23–30 cm) apart. Water regularly during establishment and in dry periods; established plants have moderate drought tolerance. Deadhead spent flower clusters promptly to prolong blooming. Allow a few plants to self-seed for succession planting. Susceptible to crown rot in poorly drained, wet winter soils.

Pruning

Deadhead spent flower clusters at the stem tip as they fade to prolong blooming; remove the entire stem to the basal rosette once all flowers on that stem have finished. For biennial cultivation, remove spent plants entirely after seed set in midsummer and replace with new seedlings for the following year's display. Perennial strains can be cut back to the basal rosette after flowering to encourage a second flush of growth and possible rebloom.

Pruning Schedule

J
F
M
A
M
J
J
A
S
O
N
D
summer

Maintenance Level

moderate

Container Growing

✓ Suitable for container growing

Minimum container size: 2 gallons

⚠️ Toxicity Warning

Toxic to pets