How to Dye Wool Yarn with Decorative Grass

Materials & tools you'll need

Step 1 — Prep the wool skein

Soak your white wool skein in hot water with a little soap, working it gently so the water reaches through the whole skein. This cleans off any residual oils or processing agents that could otherwise block the dye from taking evenly. Rinse the skein thoroughly until the water runs clear of soap, then set it aside to dry completely before moving on to mordanting.

Step 2 — Brew the grass dye bath

Fill a pot with regular water and add all of your collected purple-colored decorative grass tops — around 10 to 15 seed heads is enough for one skein. Let the mixture sit for an hour or two, checking on it every half hour or so as the color slowly releases from the grass into the water. Don't be surprised if the liquid looks quite different from the green you're expecting at this stage — the color often shifts as the dye process continues.

Step 3 — Mordant the wool with alum

While the dye bath continues simmering gently on low heat, dissolve one tablespoon of alum powder into a separate pot of hot water. Heat this alum solution at medium-low heat until the powder is completely dissolved, with no visible granules left in the liquid. Add your pre-cleaned wool skein to the alum solution and let it sit for an hour to an hour and a half. This mordant step helps the wool fibers bond with the natural dye so the color takes hold properly instead of washing back out later.

Step 4 — Let the dye bath rest overnight

Once the wool has finished its time in the alum mordant, leave the grass dye bath to rest undisturbed overnight. This extended rest gives the dye extra time to fully develop in the water before the wool goes in, which makes for a more even, saturated result than a same-day dye bath typically produces.

Step 5 — Filter and finish dyeing

The next day, strain the dye bath through a fine strainer or cloth to filter out all the plant material, leaving you with a clear, colored liquid. Soak your pre-mordanted wool skein in this filtered dye bath, checking periodically until you're happy with the depth of color. Don't be surprised if what started as purple-red grass fronds produces a soft, gentle green in the wool instead — and keep in mind the color may lighten a little further once the finished skein is washed.

Frequently asked questions

How much decorative grass do I need to dye a skein of wool?
Around 10 to 15 seed heads of purple-colored decorative grass is enough to dye one wool skein. The exact color strength will vary depending on how fresh the grass is and how long you let the dye bath sit.

What safety precautions should I take when dyeing with alum?
Alum powder and the acidic materials used in this process should always be handled with safety equipment such as a mask and gloves, and you should avoid ingestion or skin contact.

What color does decorative grass dye wool?
Despite starting with purple-red grass fronds, the finished wool comes out a soft, gentle green — a common surprise with natural dyes, since the dye color often differs from the plant's own color. This green may lighten further after the yarn is washed.

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