Wood sorrel, Oxalis acetosella
Wood sorrel, or common wood sorrel, is found in Finland in spruce (fir) forests and in mixed forests as far north as Oulu. This delicate plant grows well in shaded areas, and can be easily identified by its heart-shaped leaves.
Wood sorrel is well suited for making dyes for natural fibres. Woollen yarns, for example, can be dyed different shades of blue with the plant. The leaves of wood sorrel have an acidic and salty taste. They can be used in salads, in small amounts.
Something to try
Dyeing woollen yarn blue
100 g dried or 1 kg of fresh wood sorrel leaves and inflorescences (the flowering parts)
20 g of alum (a binding agent that helps the dye to be retained by the yarn)
100 g woollen yarn
First prepare the dye.
Chop the wood sorrel into thin strips and put in a saucepan.
Add enough water to just cover the sorrel.
Cook for about two hours.
Pour the mixture through a sieve to remove the plant material.
Add enough cold water to give 3-5 litres of dye.
Add the alum to the dye and stir well.
Wet the woollen yarn with lukewarm water and add the dye.
Slowly bring the mixture to boiling point over a low heat, stirring occasionally for about an hour.
Let the yarn soak in the dye for a few days.
After that, rinse the yarn thoroughly and allow it to dry in a shaded place.
Gathering the plants
Wood sorrel leaves can be picked throughout the growing season, and the flowers can be picked in May-June. It is not recommended to consume large amounts of wood sorrel, because it contains considerable amounts of oxalic acid, which is harmful to humans at high concentrations.
Other interesting facts
Due to the oxalic acid contained in wood sorrel, it was in the past used to remove ink stains from fabrics. Oxalic acid is still used for in conservation work, and for cleaning old objects.