Dianthus barbatus Seeds | Sweet William
LATIN NAME: Dianthus barbatus
COMMON NAME: Sweet William, Dianthus
Plant Profile
Sweet William is a short-lived perennial that gardeners treat as a biennial, and it earns that treatment by flowering best in its second year. Plants make tidy clumps of flat, grey-green leaves, then send up 30-60 cm stems carrying dense, flattened heads of fringed flowers in a single colour or, more often, a mix of white, pink, crimson and near-black purple.
The scent is clove and carnation, strongest in the evening, and it belongs to the same genus as the florists carnation. Flowers open in late May and continue for six or seven weeks if deadheaded, and a plant left to seed will scatter itself gently around the parent.
The species comes from the mountains of southern Europe, where it grows in thin grass and open woodland edges. That background explains its tolerance of poor soil and its dislike of wet winters, which kill more plants than cold does.
Science & Biotechnology
The clove note comes from eugenol, the same compound that dominates clove oil, produced in the petal tissue and released most freely at dusk. Dianthus petals have been eaten for centuries as a garnish and a flavouring; the white base of the petal is the sweet part and the coloured edge is bitter.
Dianthus is a genus of roughly 300 species centred on the Mediterranean and Asia, with a long history of hybridisation that makes garden names unreliable. Sweet William crosses with other biennial pinks, and seed saved from a mixed planting will drift within a few generations.
One practical piece of biology: the species needs vernalisation, a period of cold, to initiate flowering. A spring sowing will usually grow leaf all summer and flower the following year, while a late-summer sowing flowers on a shorter plant.
Uses & Benefits
Sweet William is a cottage-garden staple for the gap between spring bulbs and the main perennial show. It suits the front of a border, a pot by a door and the cutting garden, where its short stems are ideal for jam-jar posies. The flowers last a week in water and hold their colour when dried.
Petals are edible and are used to decorate salads, syrups and cakes, though only flowers grown without pesticide should be eaten. In the garden the plants are short enough to naturalise in grass and sturdy enough to go through a windy site without staking. Seed heads feed goldfinches if left standing into autumn.
Growing from Seed
Sow in June or July for flowers the following summer, at 18-20°C, barely covering the seed, with germination in one to two weeks. Sow in autumn instead and the plants will flower on shorter stems in their first year, which is useful for pots but less useful for cutting.
Transplant at 25-30 cm apart into ordinary soil in sun or light shade, and water until established. Do not feed: rich soil gives soft growth and fewer flowers. Stake only if the site is exposed. Deadhead to prolong flowering and to stop the stems going limp in rain, but leave a few heads to ripen if you want the self-sown drift that makes the plant look as though it belongs.
Our Take
Cheap, generous and quietly old-fashioned, it fills the early-summer gap better than most things at the price. Leave a few heads to seed and it will place itself where it wants to grow.
Related Reading
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