An article by Ashley Walker
© copyright 2016
Weld or Dyer’s Rocket (Reseda luteola) is a UK naturalised biennial wild flower that prefers to grow on chalk or limestone soil. It has pale yellow flowers and can grow to over two metres in height in its second year. The adult flowering plants are often seen growing in great masses on waste land or recently disturbed ground and may then mysteriously disappear only to pop up somewhere else another year. It has one common close relative, Wild Mignonette (Reseda lutea) which can also be used as a dye plant. Sweet Mignonette (Reseda odorata) is a closely related plant from the Mediterranean often grown in gardens for its attractive scent and as a bee attractant. All of these plants are well known for their perfume which is particularly noticeable when the plants are dried.
Weld is a Biennial
As a biennial, Weld is usually expected to grow from seed into a “rosette” in the first year. A rosette is a ground hugging form, where all the leaves grow from a central point. The plant goes through the winter as a rosette, when there may be some die back during cold frosty weather. In the Spring the rosette grows new leaves and the central stem starts to emerge into a tall flower spike. Once flowering is over the plant is expected to die. Well that’s the official line, but anyone who has grown biennials will know that it all depends on how the plants are grown (see photo).
Left to its own devices, weld seeds get scattered from mid-Summer onward. Some of these seeds will fall to the ground and germinate during late Summer and Autumn and grow into rosettes as expected. Other seeds will lie dormant in the soil and await an opportunity to germinate, usually afforded by a disturbance to the soil (animals rooting about for grubs or roots or a gardener tilling the soil). These seeds will take their chances to germinate at any time of year when the weather is warm enough. Some seeds will germinate in early Spring and, if the conditions are right, may complete their entire life cycle in one year. If the plants are stressed for any reason e.g. by drought or physical damage, they are even more likely to flower. The later in the season the seed germinates the more likely it is that it will flower in the following year. Weld’s rather random flowering behaviour makes it an awkward plant to cultivate. It is also highly sensitive to any kind of root damage, so transplanting seedlings invariably results in numerous casualties and transplanting an adult plant is almost impossible. It is quite often the case that the best plants the garden grows are those that have self-seeded in a path or on the vegetable patch – in fact anywhere except the bed you have set aside for growing Weld! It is not for nothing that Weld is generally regarded as a pioneer plant – one of the first to colonise waste ground.
The gardener interested in growing Weld for dyeing will seek to grow as large a plant as possible. This means allowing the rosette plants to build up good food reserves in their deep tap roots before shooting that ‘rocket’ of a flower spike up into the sky. This requires a certain amount of garden pampering and a choice of strategies.
Sow seed thinly into modules in early April under glass or indoors. Do not cover seeds with compost as light helps them to germinate. When the plants have grown to around the five to ten leaf stage, carefully plant out into prepared beds in mid-May. Do not add any fertiliser to the soil as research shows dye yield falls with increased nitrogen, but do water as needed. Continue to water the young plants, particularly in hot weather, and weed throughout the year. With luck, some of the plants will grow large and flower in mid or late summer when they can be harvested.
Sow seed thinly into modules in late August and plant out carefully when large enough and water regularly, particularly in hot dry conditions. Allow to grow and go through winter and they will flower in June/July the following year.
Obtain some seed heads from wild Weld and scatter the seeds in great quantities directly onto prepared beds in spring. Keep beds watered and weeded. Scattering a few organic approved slug pellets will help to protect the young seedlings which may or may not germinate.
Now if this all sounds a bit hit and miss, it is! When I grow the seeds under glass or indoors I certainly get excellent germination but lose many seedlings on planting out. Enough, however, survive to produce adult plants some of which I allow to set seed. If this is done over several years the seeds accumulate in the soil and self-seeding will start. Note: to stand any chance of self-seeding the soil must be kept bare i.e. free of weeds and any kind of mulch (mulch suppresses seed germination and harbours slugs and snails). Remember, Weld is a pioneer plant and does not like competing with vigorous perennial weeds. Small rosette plants can be moved from inconvenient positions if carefully dug out with a large clod of earth around the roots.
Weld does not make a particularly attractive garden plant in its rosette stage but if grown in ‘mono-culture’ it can put on a surprisingly good show when it flowers. If there are gaps in the first year Weld bed you can interplant other dye plants for added colour. Coreopsis is particularly good in this respect as it is an annual.
Harvesting the plants just after they begin to flower in June is generally considered the best time. As the leaves begin to die off the amount of yellow dye starts to diminish, however, dyestuff can be obtained from the rosette leaves and from old plants that have finished flowering. All parts of the plant except the roots yield dye, including the stalks. Weld plants can be very big and take up a lot of storage space. If the plants are hung up to dry somewhere warm, dry and dark they will remain green, but if dried in the light they will turn a straw yellow or even bleached white. They will however still give good dye colour. Once dried the plant can be chopped up to save on storage space and kept in boxes, bags, storage jars etc. in a dry place.
Harvesting from the wild
Weld is often found growing on waste or disturbed ground, road verges and rail cuttings, so it is not that likely that anyone would complain about people picking it. However, the law is clear “it is illegal to uproot any wild plant without permission from the landowner or occupier. Uproot is defined as to dig up or otherwise remove the plant from the land on which it is growing, whether or not it actually has roots”. Occasionally we do harvest from the wild but we always try to be responsible by cutting the plant stalks (not pulling up the roots) and leaving plenty of plants to seed.