Making Natural Dyes from Garden Plants

Why Garden Colour Is Worth the Faff

There is something quietly satisfying about pulling a bundle of wool out of a pot and finding it the colour of a late-summer marigold — a colour you grew, watered and picked yourself. Natural dyeing is slow, occasionally unpredictable and almost always rewarding. It also turns kitchen waste into something useful: those papery onion skins you would normally bin will dye a surprising amount of wool a warm, glowing gold.

You do not need a dedicated studio. A camping stove in the garden, a couple of old stainless steel pans and a bag of alum are enough to get started.

What You Will Need Before You Begin

• Dedicated pans and utensils — once they have held dye or mordant, never use them for food again.
• Scales accurate to a gram, plus a notebook and pencil.
• Alum (potassium aluminium sulphate) and cream of tartar for the mordant bath.
• Ferrous sulphate (iron) for modifying colours — effective, but use it sparingly.
• Soft water if you can get it; rainwater is ideal. Hard water shifts colours, often dulling them.
• Rubber gloves and an apron. Natural dyes stain hands and worktops cheerfully.
• Fibre: wool, silk, cotton or linen. Wool takes natural dye most readily of all.

Scour and Mordant First

Nothing dyes well if it is greasy or dirty. Wool straight from the fleece needs a gentle scour in hot water with a little pH-neutral soap — no agitation, or it will felt. Yarn and fabric should be washed thoroughly and rinsed.

Mordanting is the step that makes colour stick, and skipping it is the most common reason a beautiful dye bath washes straight out. Dissolve roughly 10–15% alum and 5% cream of tartar by weight of dry fibre — so 10g alum for 100g of wool — in hot water, add the wet fibre, and hold the bath at around 80°C for an hour. Do not boil wool; it goes harsh and brittle. Let it cool in the bath overnight if you have the patience. Cotton and linen benefit from a tannin dip first — tea, oak galls or rhubarb leaves will do — followed by the alum bath.

Plants That Actually Deliver

• Onion skins. Save them in a paper bag through the winter. Roughly equal weights of skins and fibre give rich golds and coppers. Simmer the skins for an hour, strain, then add the fibre and simmer gently for another hour. A dip in iron afterwards turns it a handsome olive-brown.
• Beetroot. Gives a lovely pink on wool, but it is a fugitive dye and fades in sunlight. Use it for items that will not live on a windowsill. Peelings work as well as whole roots, and the colour is best on animal fibres.
• Marigolds. Calendula and tagetes both dye generously, giving clear yellows and golds. Use the flowers fresh or dried, at roughly equal weight to the fibre. An alum mordant keeps them bright; a pinch of iron saddens the yellow towards olive.
• Nettle. A free crop from any hedgerow. Gives soft greens and grey-greens on alum-mordanted wool, and takes well to an iron afterbath.
• Dahlia flowers. Surprisingly good, especially the dark red and bronze varieties. Collect the blooms as they fade and use them fresh.
• Rhubarb. The leaves are rich in oxalic acid and useful as a mordant assistant for plant fibres; the roots give soft yellows and browns.

Always Test Small Samples First

This is the single most useful habit in natural dyeing. Before you commit a jumper's worth of wool, dye a small skein or a 10cm square of fabric. Weigh it, mordant it exactly as you plan to mordant the full batch, and dye it alongside a scrap of the same fibre left unmordanted so you can see the difference the mordant makes.

Keep notes: date, plant, weight of dyestuff, weight of fibre, mordant, temperature, time and water source. Colours vary wildly with the season, the soil and even the pan. Marigolds picked in June will not give the same shade as those picked in October. Without notes, you will never repeat the results you love.

Getting the Best from Your Dyes

Simmer, do not boil, for most plant dyes. High heat dulls colours and damages wool fibres. A longer soak often deepens a shade more kindly than more heat. After dyeing, rinse in water of the same temperature as the bath — a sudden cold shock can set creases in wool that are difficult to shift.

Dry dyed fibre in the shade. Sunlight is the enemy of most natural colours, beetroot especially. Store finished pieces away from direct light, and expect a gentle softening over the years; that is simply part of the character of naturally dyed cloth.

Finally, do not be disheartened by a muddy result. Overdyeing is your friend. A disappointing yellow dipped briefly in an iron modifier becomes a respectable olive, and a pale pink overdyed with onion skins turns a warm apricot. Every pot teaches you something, and the second batch is always better than the first.