Woad is a biennial which grows to about 1.5m tall. It has blue grey foliage topped by acid yellow, long lasting flowers in spring and early summer. It should be sown direct into the soil in the autumn or spring and in the first year will make a rosette of strap-like leaves. The flower stem shoots up in the second year. Bees and hoverflies enjoy the nectar and pollen and the seed set is prolific. It will tolerate most soils and sun or light shade. Good at the back of a border, and will hold its own amongst shrubs. Dye is extracted from the first year leaves by mashing in hot water and using sodium nitrate to precipitate the dye.