By Ashley Walker
Copyright 17th February 2020

Dyers broom, Dyer’s whin and Woadwaxen

Dyers Greenweed is a member of the Fabaceae or legume family. It is a typical shrubby broom native to the UK, growing in open pasture and heathland. It is a source of an excellent light fast lemon yellow dye similar to Weld. As its name suggests it was used with indigo (from Woad) to dye textiles various shades of green.

Horticulture

Like some other native dye plants, Greenweed has declined with the rise of modern agriculture so you are less likely to be able to forage for it. It mostly grows in the West and South of England and appears to prefer slightly acidic loamy clay soils though it will grow in alkaline soils if treated well. It can grow to a height of 1 to 2m and forms a bush, usually growing from a single base stem. There are dwarf varieties and a dwarf subspecies Genista littoralis. It is extremely hardy (surviving temperatures as low as -35ºC) so it should be possible to grow it in the far North. It loses its leaves in the winter and this maybe the reason it’s able to stand the sub-zero temperatures. It does not like being waterlogged but struggles in dry soils too when it needs to be watered occasionally during hot summers.

Propagation

The seedpods of Greenweed turn black in late summer and on hot days burst apart scattering the  small pea shaped brown seed.

These may germinate in the Autumn or stay in the soil and germinate in the following spring. When I first tried to grow the plant from seed I followed the instructions to plant in the Autumn. Although some of the seeds germinated I found that the seedlings died during the winter. so I changed my strategy to planting in Spring which works very well and allows the seedlings to grow large enough during the first year to get through winter without problem.

Start seeds off indoors in modules or seed trays from March to April and plant out in June in a sunny position.

The plants will grow large, so give them plenty of space and plant about a metre apart. They can be grown as a hedge in which case plant closer (say 20 to 25cm). The seedlings are very prone to slug and snail attack, so sowing the seed outdoors is very risky without protection. Cuttings can also be taken. Cut the woody 1 to 2 year old stems in Spring or Summer and just stick them into the soil. Only about 10 to 50% will take so plant more than you need. They will need watering regularly during the summer as they take a month or two to root.

Pests and diseases

Apart from slug and snail attack when young, the next big problem is aphids, which attack the young shoots in early Summer just when you want to be picking them for dye. The damage can be extensive and I sometimes have to resort to spraying them off with a jet of water from the hosepipe. Ladybird and hoverfly larvae usually get the aphid under control by mid to late Summer and the plants will recover enough to flower. There appears to be quite a bit of natural variation amongst plants with some consistently being attacked and others being generally free of the bugs. So if you find you have a resistant plant don’t hesitate to take cuttings from it.

Deer and other large herbivores also like to eat Greenweed.

Maintenance

The young shoots are best for dyeing. As the plant gets older it produces fewer shoots so the bush needs to be pruned or cut back at least once a year to encourage this new growth. In earlier times when the plant was grown as a source of dye it was typically harvested in the second year when the whole plant was cut down. During the early Spring/Summer take the first harvest of young shoots then cut back in August to get a second growth and harvest. Growing this plant as a low hedge is ideal.

As a member of the legume family, Greenweed is capable of fixing nitrogen in its root nodules. As a result the plant does not need much, if any fertilizer and can grow on quite poor soils. Don’t plant Greenweed in your most fertile bed, so choose instead any bit of scrappy ground that gets full sun. Greenweed will not grow in heavy shade. Against a South facing wall or fence would be ideal. To help keep weeds down after planting you can add some thick mulch around the stems. Water if the soil becomes very dry.

Cultivars

Greenweed is grown as a decorative garden plant for its bright display of yellow blossom in mid to late Summer. If you grow several plants from seed they will probably have slightly different flowering times but if you buy a commercial cultivar each plant will flower at the same time. Commercial cultivars may also be less able to cope with strong pruning and are usually a lot smaller than the wild plant. Three cultivars of note are:

• Royal Gold – 0.5 to 1m
• Humifusa – dwarf variety
• Flore Pleno – dwarf variety

Dyeing

The leaves and young shoots are treated much like Weld except if the stems are woody strip the leaves first. Boiling water is poured on the cut shoots and left for an hour or so to extract the dye. Fermenting the young shoots can also have excellent results. A small amount of alkali (lime water or a drop of ammonia) will bring out the yellow. Dye your textiles in the resulting extract at around 70ºC. This dye is excellent for silk. If dyeing green with indigo a slightly better result will be obtained if you dye indigo first and then over-dye with  Greenweed. The young shoots can be dried for storage and later use.