Friday, 21 June 2019

Cultivating Weld Plants for Dye

I walked out into the garden thinking this could be the perfect day for sowing weld seeds and as I reached the greenhouse, my companion jumped up in delight. The miserable June weather has forced her to move her deckchair inside and while the interior of the new greenhouse does provide an exclusive orangery ambiance, mobile phone reception is so dodgy that the poor soul often has to trek back to the house to order her tea and biscuits.
"Feeling parched and peckish again, Elinor?" 
A gust brought rain in through the greenhouse door and mud splattered the gravel as I dumped down half a sack of sodden seed compost. My companion shuddered and stepped back.
"Do shut the door - if you care nothing for me, at least spare a thought for your chilli peppers. I can't think why you're bringing in compost, Beaut. This weather might feel like April but it's far too late to be sowing seeds."
I wiped my hands on my jeans and the rain off my specs.
"The summer solstice is upon us. Weld seeds germinate best with lots of light and since this is the longest day of the year, it must surely be a good time to start sowing next year's weld plants."

I usually sow all my dye plant seeds in March. The seed trays sit on the underfloor heating in the bathroom and within a matter of days, tiny shoots appear and off they go, out to the greenhouse to grow on. Weld is the only plant with delayed germination. I've found that even when seeds are sprinkled on the surface of the compost with no earth or vermiculite on top, they remain inert until they get not only warmth but really decent light. Still, sooner or later, weld seedlings do appear in the March sown trays and although officially a biennial, with an early start, most of the plants will flower the same summer. 

This year's March sown weld plants are presently modest clumps of leaves, half of which have put up flowering spikes about 40cm high. They'll grow bigger and when I cut the main spikes, plenty more will shoot from the lower leaf axils. A few young weld plants won't flower, they'll just remain as low rosettes of leaves. Next spring, those will grow into plants 1.5m tall which start flowering by the end of May.

Weld flower spikes provide a great weight of material and thus a better harvest of luteolin dye than picking individual leaves from young clumps. Spikes are also simple to hang up in bunches to dry and dried weld leaves store their strong yellow dye for at least five years. Once they have finished flowering, the weld plants die. Since the second year plants grow so much bigger and generate ten times as much material as those that flower in their first year, it has become clear to me that though you have to wait longer, it's altogether more productive to cultivate weld as a true biennial. I've tried sowing fresh seed in September, straight from the last of the weld spikes, but once again, have found germination is uncertain. Maybe that's because the plant has been forced to go on flowering unusually long because I've picked spikes til the end of August and by September, the light levels are diminishing with the season. Left unpicked, early weld flower spikes would be setting seed already which would be scattered by the wind around the summer solstice. 
So theoretically, I reckon today could be the ideal time to sow weld. Even if there's little sunshine, we do have have long hours of daylight. Next week it's due to get warmer and I'll try to remember to put up another photo of that seed tray. See how long it takes the seeds to germinate.

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