Woad is a biennial plant. In the first year, it forms a low-growing cluster of leaves like spinach.
It is at this stage that the leaves are harvested for dye production because they have little or no colour when they reach the second year.
In the second year, the plant produces tall stems five feet in height that are surmounted by sprays of small, neon yellow flowers.
The leaves become longer and thinner and the plant looks quite different.
After producing seeds, the plant dies down.
Sowing Woad Seeds
The seed is sown thinly spaced in either March or November, in shallow drills or in seed trays, just covering the seed (the video shows seeds planted in drills in March 2007).
The seedlings are transplanted a foot apart when they are large enough to handle. Woad likes an alkaline soil, so apply lime to the soil about a week before transplanting. For dark colours woad needs plenty of nitrogen, which it can get from fertilisers such as dried blood & bone meal or hoof & horn meal.
Planting out Seedlings
Like other plants of the cabbage family, woad is susceptible to club root. The crop needs rotating and woad cannot be planted where broccoli or other brassicas have been grown.
If your area is infested with club root, you may get away with transplanting the woad into pots, letting it grow for a couple of weeks or more and then transplanting it into the final position.
Harvesting leaves for dye extraction
Woad planted in November can be harvested from end of June till early August. Woad planted in March can be harvested from July until September. In some years, woad can be harvested as late as November but the first autumn frost may destroy the colour. Some people manage to get colour all the year round.
Use secateurs to cut the woad leaves, avoiding old leaves with blue in the leaf stalk, and leaving as much leaf stalk behind as possible. It is better to cut all the leaves of one plant, so as to let the new leaves grow again.
The leaves can now be used for dye extraction!
Collecting woad seeds
When the harvest is finished, leave a couple of strong plants for seed production. It is best to dig up the other plants before they become too large and, therefore, hard to dig up.
Collect all the seeds as soon as they are ripe. Be careful not to let woad self-seed, as it can be an invasive plant (see Facts about Woad). It does not however spread vegetatively.