A group of Weld, Reseda luteola, plants growing at the edge of a field near Norwich (mid June 2020).

In the last couple of years I have grown Weld, Reseda luteola, in the garden.

Weld is a biennial. In its first year it forms rosettes of narrow, dark green, shiny leaves. These have a prominent white mid-rib and are often crisped and wrinkled like angled aluminium tent pegs. Below ground, the plant forms a long tap root.

In its second year, Weld grows upwards, producing flowering shoots to 1.5 metres (5 feet) high or sometimes more. These often branch towards the tip and bear racemes of pale yellow flowers from June onwards. As the plant ages the plant often takes on an orangey-yellow tinge, as the rear plants have done in the photograph above.

In the British Isles Reseda luteola is thought to be an archaeophyte (an ancient introduction). It is native to Eurasia and parts of North Africa, including Egypt and Libya, Portugal, Spain, Albania, Bulgaria, Greece, Italy and the former Yugoslavia, Afghanistan, Cyprus, Iran, Iraq, Turkey and Pakistan. It has been introduced into North America and parts of Australia.

Weld is a member of the Resedaceae, the Mignonette family. Worldwide, the family contains 107 known species in 8 to 12 genera, but in Britain we only have five species of Reseda and you’re most likely to encounter just two of them: Weld (Reseda luteola) and Wild Mignonette, Reseda lutea (note 1).  Wild Mignonette is also a biennial but it is a shorter plant with divided leaves. My way of remembering the difference between the plants is that Wild Mignonette has divided leaves but Weld’s are entire – as if they have been welded together.

I grow Weld in the garden because I like its flowers and its upright growth habit, which allows it to fit into fairly small spaces, a useful habit if you want to grow a wide range of plants.

But my main reason for growing Weld is to attract Yellow-face (Hylaeus) bees, especially the Large or Mignonette Yellow-face Bee, Hylaeus signatus. In Britain the female bees only collect pollen from Weld and Wild Mignonette and even a single plant (which is all I have room for) will attract the females and also groups of males, which swarm around the flower heads in the hope of finding mates. Today is cool and damp so they have just been sitting on the flowers, but on a hot sunny day the males whizz round and round the flowers. There are twelve species of Yellow-face bees in the British Isles and nine in Norfolk; we get seven species in our garden in Norwich. Hylaeus signatus is the largest and Weld also attracts Hylaeus pictipes, the Little Yellow-face Bee, which we re-found in Norfolk in 2017 in our garden, after an absence of over a hundred years.

Large or Mignonette Yellow-face Bee, Hylaeus signatus, on Weld flowers.

Little and Large: Hylaeus pictipes (bottom left) and Hylaeus signatus on Weld flowers.

In the British Isles, Weld grows on neutral or base-rich soils, which means that it becomes much scarcer in Highlands of Scotland and in western Ireland. The Online Atlas of the British and Irish Flora lists its habitats as:  roadsides, waste ground and marginal land, in brick yards, gravel-pits and urban demolition sites, and, less commonly, arable or grassy areas.

Weld is a useful dye plant and it has a history of use from at least the first millenium BC and was reputedly used to dye the robes of the Vestal Virgins in Roman times. Nowadays synthetic dyes have mostly taken its place but the plant is still grown for this purpose. It contains significant quantities of the flavonoid luteolin, a yellow dye (note 2). Another name for the plant is Dyer’s Rocket.

The leaves or seeds of Weld are used to produce dye (note 3). The Plants for a Future website says that “the plant is harvested as the last flowers fade. Most of the dye is found in the seed.” The Wild Colours website advises that “the colour is more concentrated in the leaves, flowers and seed capsules; the stalks do not have much colour. Old, dried-up weld plants give a dull yellow.”

The Dyeing Crafts website says “Cut the plant about 10 days after the start of it flowering. The leaves, flower heads and seed capsules provide the maximum dye content. The plant can be used fresh or dried for storage to be used at a later date.” It also gives a recipe for making the dye.

I grow my Weld plants from seed. I buy mine from Emorsgate Seeds, but there are plenty of other suppliers if you do an internet search. I sow my seeds in late summer in peat-free compost in an unheated greenhouse and transplant them to their final home in late winter, before the tap root is too long. It is important not to cover the seeds with too much compost, as they need light to germinate. Seeds can also be sown in spring. Plug plants are also available from companies such as Naturescape. (I haven’t tried these, but it would be a quick way of establishing plants.)

If you want to produce a green dye (such as Lincoln Green) you can mix the yellow dye from Weld with the blue dye from Woad (Isatis tinctoria).

With apologies to Louis Armstrong, “And I think to myself what a wonderful Weld“.

Notes

Note 1 – Stace (Fourth Edition, 2019) lists Reseda luteola (Weld), R. lutea (Wild Mignonette), R. alba (White Mignonette; casual on waste ground), R. phyteuma (Corn Mignonette; rare and decreasing casual of waste ground) and R. odorata (Garden Mignonette; occasional garden escape).

Note 2 – Weld also contains two other dyes: apigenin and chrysoeriol.

Note 3 – The seeds also contain an oil that has been used in lighting.