Plant care: Woad

I would like to kick start this new series of blog posts on plant care and cultivation by looking at one of our most asked about and popular plants; Woad.

Woad (Isatis tinctoria) is arguably one of the most famous of medieval plants. As the second half of its taxonomic name suggests, tinctoria, this plant is famous for its use as a dye plant. Woad was highly prized for the blue pigment it could produce, leading to a whole industry arising in the production of this plant. Throughout the Middle Ages the major centre of woad production was in France in the Languedoc and the area earned the name of ‘Pays de Cocagne’ or the land of woad balls.

Woad is a beautiful plant, flowering in its second year of growth it produces a flower stem in May and June covered in yellow cruciform (four petaled, cross shaped) flowers. The flower stems arise from the rosette of blue green leaves and stand up to 2m tall although 1m is more usual. Originating from south eastern Europe they are a very drought tolerant species, favouring free draining, alkaline conditions.

Woad flowering in modern drought tolerant planting.

Woad dyeing shares many similarities with another famous dye plant. Indigo (Persicaria tinctoria). This plant from east Asia also produces a blue dye similar to woad, in fact the chemical constituent indigotin is identical in both plants.

We will be happy to produce a guide on Woad dying in a subsequent post, this post however is more preoccupied with the growing of this plant.

Propagation

With all dye plants quantity is important and so I shall begin with how to create more of your plants. Woad is a biennial plant, this means it flowers in its second year at the end of its life cycle. Although this may seem like a disaster it actually provides the greatest opportunity for the medieval gardener to increase their stock. Allowing the yellow flowers to bloom and set seed will give you plenty of new stock for next year. Allow the pendulous seed to dry on the flower stems, but make sure not to loose the seeds to the local birds as the seeds are very tasty to goldfinches. Store your seed in brown paper envelopes until you are ready to sow.

Woad flowers starting to develop their pendulous seeds.

Sowing seed:

sowing seed is often a scary process for new gardeners but can be the most rewarding and cheapest way to build a garden.

There are 2 options when sowing woad, directly into the ground or into trays. So far we have only found references to direct sowing in the medieval period, but sowing into trays can help keep closer eye on seedling development.

Seeds should germinate 2 weeks after sowing, but may take another week or 2. If no germination occurs after 4 weeks then try again and consider getting a hold of fresh seed.

Timing your sowing is also an important part of the process, If you are direct sowing then woad should be sown in the spring after the last frosts into a prepared bed. Clear the ground and rake the soil to a fine crumb. Seeds can be sown over the top and gently pressed for good contact with soil.

For tray sowings this can be done slightly earlier if protected in a greenhouse or on a windowsill.

Plants sown in trays will need pricking out once they are large enough to handle. Gently tease each seedling out of the trays by grasping their seed leaves, and gently teasing the roots out with a pencil or seed label. The seedling can then be carefully potted up into individual pots to grow on before being large enough to go in the ground. By using trays you can have strong seedlings ready to go for the last frost and get large plants ready to harvest by the end of summer.

Potential problems

With all garden plants there are known issues. Woad is no exception.

Pests:

Woad is a member of the Brassica family and as such can suffer from many of the same pests. Cabbage white butterflies in particular will be all too happy to munch through a woad patch. Being diligent in picking off caterpillars will protect your crop, these can be fed to your local birds or can be a favourite snack of chickens.

Caterpillars like this cabbage moth can be physically removed to minimise damage

Disease:

Woad as previously mentioned is a relative of cabbages, and so suffers from many of the same diseases. The main problematic one will be cabbage clubroot. This disease will distort the roots of your plant, and dwarf your plants. The disease can linger in the soil and so if growing large quantities of Woad the location of your woad patch should alternate each year. Try to avoid growing woad with other Brassicas to help minimise the risk of this disease.