Updated: Apr 20, 2020
Woad was formerly widely grown in Britain as a source of blue dye, which was extracted from the leaves after they had been dried, powdered, and fermented. In medieval times there were important woad-growing regions in England, Germany and France. The first archaeological finds of woad seeds date to the Neolithic. Woad contains the same blue pigment as indigo, byt in lower concentrations, and as such when the indigo trade began, the growing on woad was no longer profitable and went out of fashion in europe. Native to Central Asia through to Eastern Siberia and Western Asia. It is now also found in Central Europe and Western North America. Woad is a biennial plant that in its first year forms a rosette of leaves, and in the second year of growth produces large heads of yellow flowers. It is the woad leaves in the rosette form, not the flowers, which are used for dyeing.
Woad seeds are sown in Spring around April or in Autumn, and do not require much warmth to germinate. The seeds have a germination inhibiting coating around them that needs water and constant moisture to dissolve. Generally the seeds will germinate in about two weeks, each seed can actually produce multiple seedlings. When sown in spring the woad plants should be in their rosette form and ready to harvest in July all the way through September. When planting in soil blocks from our kits, plant 2-3 seeds per block and allow them to grow until they have their first true leaves, they can then be carefully separated and planted out into their final growing position or onto larger pots. Woad seeds can also be sown directly into the soil once the risk of frost has passed, but it may be difficult to determine the difference between your seedlings and competing weeds. When planted in the autumn, some plants will remain in the rosette stage into the following year for harvest in early summer.
Woad is best grown in the ground leaving at least 30cm between plants. To get a good yield of pigment from your plants, they require rich soil and benefit from the addition of fertiliser such as chicken manure. The amount of pigment in the leaves is dependent on many factors, including the stage of the plant and the climate. The amount of pigment increases in hot and sunny conditions, but as soon as the plant begins to flower the amount of pigment falls dramatically, if the plants start to flower you can cut the flowering stem back to attempt to increase pigment again in the leaves. If left to flower, large amounts of seeds can be saved for planting the following year.
To harvest, use sharp pruning shears or garden scissors and select healthy fresh leaves. Once harvested the leaves should be used the same day, drying will result in loss of the pigment.