On Sunday I havested the woad seeds which have been growing on the allotment for about 13 months now. They are big heavy plants! Hopefully combined with some alum mordant I might get some pinkish or pale greenish hues. If not I have alot of fresh seeds for next year. I start my seeds off in 3" pots of compost (2 per pot then thin the weaker seedling or carefully transplant, watch the big roots which do n't like being disturbed) in a cold greehouse about mid April time. They are easy seeds to germinate so as long as it does n't go into the low minus tempratures. When danger of frost has gone (end of may-ish) I plant them in a fertile patch about 2 foot apart as they can reach over 5 foot in height. The better your soil the more blue pigment you will receive. Woad plants are very greedy feeders and are biennial so look after your soil as if in my case they are on an allotment not much will grow well afterwards if you have n't mulched / composted / mucked you ground at the end of the year. In the first year harvest leaves before the first frosts come (September) to get decent blue colours as people say the dye pigment gets ruined by the cold. I have no experience of that but am not going to risk finding out! Either use fresh or dried. There are many good receipes out there to follow for experimenting with. I use the book Wild color by Jenny Dean. In the second year huge flower spikes with yellow brassica flowers form in May and then seeds in June. These might need staking as they are prone to blowing over and other than a water in dry spells it is easy to grow. The only problem I have encountered is munching insect friends so watch if you want perfect leaves and pick off slugs. Cut down seed spikes as it can be an invasive bully of a plant if left to self seed and will quickly fill your plot!