Stock (Matthiola incana): growing, history and varieties
Biology and botanical characteristics
The stock, also called garden stock or ten-week stock, belongs to the Brassicaceae family, formerly known as Cruciferae. Its scientific name is Matthiola incana.
It is a herbaceous plant generally grown as a biennial in temperate regions (summer sowing for spring flowering), although some modern varieties are treated as annuals for quick summer flowering.
Its habit is upright and bushy, with a height of 20 to 80 cm depending on the cultivar. The simple, lanceolate to spatulate leaves are covered with a dense felt of trichomes that gives them a characteristic grey-green colour and a rough feel.
The flowers form elongated terminal clusters, followed by axillary racemes. Each flower has four petals arranged in a cross, the typical symmetry of the Brassicaceae. The colour range runs from white and cream to pale yellow, pink, carmine red, violet and deep purple. There are single-flowered varieties, often more fragrant, and varieties with dense, pompon-like double flowers.
The fruit is an elongated silique that opens by two valves and contains numerous kidney-shaped, reddish-brown seeds. The scent is sweet, powerful and penetrating, particularly marked in the single forms and often more intense at dusk.
History and geographical origins
The stock is native to the coastal and mountainous regions of the Mediterranean basin. It grows wild on limestone cliffs, rocky screes and fixed dunes in southern Europe, notably in Sicily, Malta, Crete, Greece and the Balkans.
The genus name Matthiola honours Pietro Andrea Mattioli (1501-1578), an Italian physician and botanist renowned for his illustrated commentaries on Dioscorides. The epithet incana refers to the whitish (canescent) felt of its foliage.
Introduced into botanical and aristocratic gardens from the Renaissance onwards, it was first admired for its cold resistance and its scent. From the 19th century, European breeders intensively selected double-flowered and giant strains, then in the 20th century varieties resistant to heat and rain for professional cut-flower production.
The origin of the French common name "quarantaine" (literally "forty days") is uncertain. It may come from how quickly it grows when sown early under heated cover (about forty days from sowing to bolting) — hence the English "ten-week stock" — but no explanation has been established with certainty.
Growing and care in the garden
Position and climate
Stocks need full sun to flower well. A position sheltered from prevailing winds is preferable, especially for tall-stemmed varieties grown for cutting. They like cool temperatures and tolerate light to moderate frosts once mature, but young seedlings and plants in flower are sensitive to hard frost.
Soil and feeding
Choose a light, well-drained, airy soil. Stocks cope with poor, stony or chalky ground, and dislike heavy, waterlogged soils that cause rot. A neutral to slightly alkaline pH (6.5 to 7.5) is ideal. Avoid nitrogen-rich fertilisers, which encourage excessive foliage at the expense of flowers.
Sowing and planting
Sow in open ground or under cover in small pots. For early spring flowering (grown as a biennial), sow from June to August. For summer flowering (grown as an annual), sow from March to April. The seeds are tiny: mix them with fine sand to spread them evenly and barely cover them.
Germination takes 7 to 14 days at 18 to 21 °C. Prick out into individual pots at the two-true-leaf stage, then plant out 25 to 40 cm apart depending on the cultivar's vigour. Plant up to the level of the seed leaves to keep the plant stable.
Growing on
Water moderately, at the base of the plant, avoiding wetting the foliage to limit fungal diseases. Pinch out the growing tip of young plants (6 to 8 leaves) to encourage side branching and get more flowering stems.
For cutting varieties taller than 60 cm, discreet support with mesh or netting is recommended. Regularly remove faded flowers to prolong flowering and prevent premature seed setting.
Propagation, harvest and uses
Sowing and saving seed
Propagation is almost exclusively by seed. Seeds keep for 3 to 4 years in a cool, dry place. Note: F1 hybrid varieties do not come true from home-saved seed; choose stable strains or heritage varieties for controlled reproduction.
Cuttings and other methods
Softwood cuttings are theoretically possible from non-flowering stems, but the success rate is low and development is slow. This method is marginal and reserved for conservatories of rare varieties. Neither layering nor division is possible because of the taproot.
Cut flowers and bouquets
For cut flowers, cut the stems early in the morning when two or three flowers at the base of the spike are open and before the stamens dry out. Conditioning in fresh water with a clean, slanted cut improves vase life, which reaches 7 to 12 days depending on the variety.
Mature siliques can be used in dried arrangements for their architectural look. Single flowers attract nocturnal and daytime pollinators, notably butterflies and bees.
Diseases, pests and other problems
Fungal diseases
- Grey mould (Botrytis cinerea): encouraged by stagnant humidity and cool temperatures, it causes brown wilting and grey fuzz on flowers and lower leaves.
- Crucifer powdery mildew (Erysiphe cruciferarum): appears as a white, floury coating on the leaves and can distort them.
- Damping off (Pythium, Rhizoctonia): causes sudden stunting and collapse of the seedling stems in hot, humid greenhouses.
- Blackleg (Phoma / Leptosphaeria maculans): blackish spots on the stem leading to the plant dying back.
Pests
- Flea beetles (Phyllotreta and crucifer flea beetles): jumping insects that pepper the foliage with small, round, translucent holes.
- Cabbage aphids (Brevicoryne brassicae): green or grey colonies on buds and flowers, vectors of viruses.
- Large white caterpillars (Pieris brassicae): green and yellow larvae devouring foliage and flower buds.
- Cutworms and slugs: attack seedlings and young plants in damp conditions.
As a member of the Brassicaceae, the stock attracts the same pests as cabbage and oilseed rape. If cabbage white pressure is high, consider insect netting over early sowings.
Sourcing and available varieties
The trade distinguishes garden varieties intended for amateur gardeners from those reserved for professional cut-flower production. Seeds are sold in colour mixes or as pure strains.
Notable varieties
- Brompton: a tall, old biennial form (60-80 cm), with single, fragrant flowers, ideal in beds or at the back of a border.
- 'Cinderella' series: a compact variety (about 20 cm), ideal for pots and edging, available in many colours.
- 'Yellow Wonder': a variety with bright yellow double flowers.
- 'Heritage' series: includes distinct colours such as 'Heritage White' (pure white) or 'Heritage Pink' (pink).
- 'Hot Cakes': a vigorous mix prized for its uniform flowering.
Where to buy plants and seeds
Seeds are available in garden centres and online from general seed companies (Vilmorin, Fito, Kokopelli) as well as from seed merchants specialising in heritage flowers and professional varieties (Suttons, Renee's Garden, Florian).
Pot-grown plants of pre-sown biennial varieties are offered in autumn or spring in nurseries and DIY and garden superstores. For intensive cut-flower production, growers buy bare-root plants or plug trays from specialist producers.
