Woad
Isatis tinctoria · Brassicaceae
The gardener's calendar
Ideal time to plant woad: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.
ID card
- Common name
- Woad
- Family
- Brassicaceae
- Type
- Biennial herb
- Adult height
- 60 to 120 cm
- Flowering
- April to June (yellow flowers)
- Foliage
- Deciduous, blue-green
- Hardiness
- Very hardy (-15°C)
- Origin
- Mediterranean region and Western Europe
Expert tips
The key tip
Woad grows vigorously but demands well-drained soil, otherwise the roots rot come spring. Sow directly in place from March to May, as it hates transplanting. Year 1 it stays low, year 2 it bolts into flower: that's normal, plan your space accordingly.
The common mistake
Gardeners sow it too early in the preceding autumn and watch it flower/bolt that same winter, instead of letting the natural two-year biennial cycle run with winter dormancy.
The pro's trick
Harvest the dye leaves in the first year before the plant bolts. Once you see the stem elongating in January-February, the colour potential is done. If you're growing it purely for dye, remove flower buds as soon as they appear.
Seasonal watch
Autumn-winter: woad fears stagnant moisture. Soil that stays waterlogged after winter rain will kill it. On clay, raise your beds or drastically improve drainage.
Care
Sunlight
Woad appreciates a sunny to partially shaded location. It tolerates bright spots well, ideally with at least 4 to 6 hours of direct sunlight per day. Too much shade weakens the plant and reduces the production of coloring pigments.
Soil
Well-drained and fertile soil is preferable. Woad adapts to chalky or neutral soil, even slightly alkaline. Avoid overly compact or waterlogged soils, which promote root rot.
Watering
Water regularly during the first year, particularly during active growth and in dry spells. Once established, the plant tolerates drought better. Keep the soil moist but without excess stagnant water.
Fertilizing
A moderate application of balanced fertilizer in spring is usually sufficient. Avoid excess nitrogen, which stimulates foliage at the expense of flowering. Woad is not a heavy feeder and copes well with poor soils.
Pruning and harvesting
Remove spent flowers to prolong blooming. In traditional cultivation, leaves are harvested before flowering, when indigo concentration is at its highest. Cut the main stems to encourage branching.
Diseases and pests
Woad can suffer from powdery mildew in warm, humid weather; ensure good air circulation. Aphids and whiteflies occasionally target it. Apply biological treatments if necessary and remove diseased leaves.
Did you know?
Woad was the main source of indigo dye in Western Europe during the Middle Ages and Renaissance, before the arrival of pastel and exotic dyes. Its use was so important that dyer corporations fiercely opposed indigo imports from the Indies, staunchly defending their "woad blue." Fermented and processed leaves produced a precious powder that dyed fabrics a deep and lasting blue hue, highly prized by the nobility.
Where to buy it
Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.
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Tips generated and checked by Viridia — adapt them to your local climate.