Natural Dyeing with British Garden Plants

Why keep a dye pot on the go?

There is something quietly satisfying about pulling a skein of wool out of a pan of simmering onion skins and watching it turn the colour of honey. Natural dyeing asks very little of you: a large stainless steel or enamel pot, a wooden spoon, a heat source, and whatever your garden or the hedgerow is throwing away. The colours are softer and more changeable than synthetic dyes, and they shift with the seasons and the water you use. That unpredictability is part of the pleasure. Nothing beats a jumper, a cushion cover or a set of napkins that carries the particular tint of your own plot.

Mordants: what turns a wash-out into a keeper

Without a mordant, most plant colour sits on the surface of the fibre and rinses away within a few washes. A mordant binds the dye to the fibre, and it also nudges the final shade. For wool and other animal fibres, potassium aluminium sulphate (usually sold simply as alum) is the workhorse. Use roughly 10% of the dry weight of your fibre, plus 5% cream of tartar, dissolved in enough warm water to cover the goods. Bring the bath slowly to around 80°C — a gentle steam, never a rolling boil — and hold it there for an hour, then leave the fibre to cool in the liquid overnight.

Cellulose fibres such as cotton and linen are more stubborn. Give them a tannin pre-bath first by simmering them for an hour in strong black tea, then mordant with alum. A pinch of chalk in the mordant bath helps cotton take colour more evenly. Iron — ferrous sulphate — is used after dyeing, at around 2% of fibre weight, to sadden and darken colours, but treat it with respect: it is corrosive, it can make wool brittle if overdone, and a two-minute dip is usually plenty. Keep a dedicated dye pot and never use it for food again, label your jars clearly, and work in a well-ventilated space.

Onion skins: the forgiving place to start

Save your brown and yellow onion skins in a paper bag for a few weeks and you will soon have a dye bath for free. Aim for roughly the same weight of skins as fibre — about 100g of skins for 100g of wool. Simmer the skins gently for 45 minutes, strain them out, then add your wet, mordanted fibre and hold it at a low simmer for an hour. Left to cool overnight, wool emerges in shades from pale gold to deep bronze; the older and drier the skins, the richer the result.

A pinch of soda ash added to the bath pushes onion skins towards copper and orange-red, while a splash of clear vinegar keeps things on the golden side. Onion skins are also wonderfully colourfast, which makes them the ideal first experiment for a beginner.

Marigolds: sunshine in a saucepan

French marigolds and pot marigolds (calendula) both give a clear, bright yellow that lifts a grey winter room. Pick the flower heads only, deadheading your plants as you go, and use around 200–300g fresh or 50–100g dried per 100g of fibre. Fresh heads freeze beautifully, so you can collect a bagful over the summer and dye in autumn.

Simmer the heads for 30 minutes to extract the colour, strain, then dye as usual. Marigold yellows are strongest on wool and silk, softer on cotton. A quick dip in an iron bath afterwards turns them olive and sage green, which is a lovely way to get two distinct shades from one dye pot.

Nettles: colour from the wilder corner

Nettles are free, abundant and quietly generous. Cut the top few leaves of young plants before they flower, wearing gloves, and use about 500g fresh nettles per 100g of fibre. Simmer them for an hour — the kitchen will smell distinctly green — then strain and dye your mordanted goods in the liquor.

With alum alone, nettles give soft sage and olive greens on wool, and greyer tones on cotton. Adding an iron after-bath deepens them to a serious slate green that suits wool coats and heavy linen. Never strip a single patch: take a little from several stands and leave plenty for the butterflies.

Habits that make the difference

• Weigh everything. Work from the dry weight of your fibre and note quantities, temperatures and timings in a book. You will be glad of it next year.
• Soak fibre thoroughly before it goes near the pot, and add it to a bath that is already warm rather than heating it from cold.
• Heat gently. Wool felts if it is shocked, so raise and lower temperatures slowly and let the pot cool overnight.
• Rinse in water of a similar temperature, then wash with a pH-neutral soap and dry in the shade to protect the colour.
• Keep modifiers separate. A jar of vinegar, a jar of soda ash solution and a jar of iron solution, clearly labelled, give you a whole palette from one dye bath.

Start with onion skins, add marigolds when the garden is generous, and let nettles fill in the gaps. Before long you will have a shelf of dyed skeins that look like a record of your year.