Dyeing With Cosmos Flowers: A Simple Guide to Summer Color

This year, I filled a sunny stretch of my dye garden with cosmos flowers, and they rewarded me with the happiest colors I’ve seen in a long time. Cosmos sulphureus, sometimes called orange cosmos or sulfur cosmos, produces some of the most joyful natural dyes I’ve ever used. Even though I’m not a huge orange fan, I love the warm tangerine oranges and deep persimmon tones that I ended up with in this project.

an orange skein of yarn, a pile of orange fabric, and a small pile of dried cosmos flowers

Natural dyeing with cosmos is very similar to dyeing with coreopsis flowers. If you’ve tried those before, you’ll feel right at home here. Cosmos is forgiving, abundant once it gets going, and can produce a whole range of colors from lighter shades of peachy-yellow to richer orange, on mordanted fabrics and wool.

In this post, I’ll walk you through how I grew, harvested, dried, and dyed with cosmos so you can try it yourself — even if you only have a small patch of garden or a few pots on a balcony.

Growing Cosmos for Dyeing

Choosing the Right Varieties

There are different varieties of cosmos, and not all of them are strong dye plants. The ones that work best for dyeing are:

Cosmos sulphureus (orange or sulfur cosmos) — strongest dye
Yellow cosmos — also good for flower dyes

If your goal is color, focus on the orange cosmos types. These will give you the richest hues in the dye pot.

Planting and Growing Conditions

Cosmos loves sunshine. For best results, plant in full sun in soil that drains well. Cosmos isn’t picky about nutrient levels — in fact, if the soil is too rich, they may grow tall and leafy without producing many blooms. This makes them a great option if your garden is still improving and the soil isn’t perfect yet.

You can direct seed cosmos outdoors after your last frost. Simply scatter seeds over loosened soil and lightly rake them in. Keep the soil moist for the first couple of weeks until seedlings establish. Once they’re several inches tall, they’ll need only occasional watering.

By early summer, I had feathery green plants filling their bed, and before long, they burst into full bloom.

Harvesting Cosmos Flowers for Natural Dyeing

Once the plants start producing, the more you harvest, the more they bloom. I like to go out every day or two and gather the fresh flowers. This encourages the plants to keep sending up buds all season.

If you want to dye right away, you can use fresh flowers. However, most natural dyers collect over time and dry their flowers so they have enough plant materials to create a strong dye bath.

To dry cosmos flowers:

Lay them on a screen or mesh rack
Keep them out of direct sun and moisture
Allow airflow
Store in an airtight container once crisp

If you won’t be dyeing within the next couple of months, consider freezing dried flowers to keep them bright.

Equipment for Dyeing

When working with natural dyes, all equipment must be used only for dyes, not for cooking food.

two large stainless steel stock pots
large mesh strainer
tongs and/or wooden spoon
mordant ingredients (depending on fiber, see below)
portable burner (or just use your stove)
drying rack
mesh bags (for loose fibers)
kitchen scale

Making a Cosmos Flower Dye Bath

The basic ratio for cosmos dyeing is based on the weight of fiber (WoF). This means you weigh your fiber first, then measure your flowers accordingly.

For a deep orange shade:
→ Use 100% WoF (equal weight of flowers to fiber)

For lighter shades:
→ Try 25–50% WoF

Steps:

Place your dried flowers in a pot.
Cover well with hot water.
Heat to a gentle simmer — do not boil. Boiling can dull the color.
Keep at a simmer for about one hour.
Carefully strain out the flowers by pouring the dye liquid through the large strainer, into the other large stock pot. This is your immersion dye bath.

You should now have a golden-orange dye bath ready to receive fiber.

Mordanting Your Fiber

All fibers must be mordanted before placing in the dye bath. There are a few ways to do this, depending on the type of fiber being dyed.

Cosmos works beautifully on protein fibers like wool, alpaca, and silk. To mordant these types of fibers, read thorough instructions here.

It also dyes cotton nicely, though cotton benefits from tannins in the mordanting stage. A dark tannin base such as oak galls, pomegranate rind, or even strong tea can shift the color toward rustier oranges. Farm and Folk has great instructions on mordanting cotton fabric.

For the cotton yarn I dyed, I purchased Dye-lishus cotton, which doesn’t need to be mordanted due to a special treatment. This type of cotton also requires much less dye. Read more here.

Whatever fiber you use, make sure it is:

Natural (no acrylics or synthetics — they won’t take the dye)
Mordanted properly beforehand

Before adding mordanted fiber to the dye, let it soak thoroughly in warm water so it absorbs evenly.

Dyeing the Fiber

Gently place the soaked, mordanted fabrics or fibers into the dye pot.
Heat slowly and keep the temperature low and steady — again, no boiling.
Let the fiber sit in the hot dye for at least one hour.
Turn off the heat and let the fiber cool in the dye bath. This deepens the color.

Once cooled, remove the fiber and rinse gently until the water runs clear.

If you’re using wool, be mindful to avoid temperature shock or agitation to prevent felting.

Using the Exhaust Bath

Your first dyeing will usually produce the deepest colors. But don’t throw the dye bath out — cosmos is a great exhaust bath plant. Add another batch of mordanted fiber and repeat the process. The second round typically yields lighter shades — soft apricot, yellow, or honey tones that are just as lovely.

Sometimes I like to layer those exhaust bath colors with other dyes later.

The Finished Color

This fall I dyed:

Cotton fabric for quilting
Cotton yarn

I’m looking forward to dyeing more over the winter!

A Few Final Notes

Cosmos flowers and stems can be pressed and used for eco printing. The Dogwood Dyer has an excellent class on this process.
Let some of your flowers dry in the garden and go to seed. Gather and save the seeds in a dark, dry place and use them for next year’s garden.
Even a small planting can produce enough flowers for a beautiful small batch dye project.
Keep naturally dyed items out of direct sunlight as much as possible. Many natural dyes are lightfast, but all dyes (even synthetic ones) will eventually fade given enough time and sun. Cosmos dye is a bit more susceptible to fading than some other natural dyes.

Natural dyeing invites us to slow down, observe the seasons, and work with what the garden gives. Cosmos has become one of my favorite summer dye plants, and I hope you’ll enjoy working with it too.

Watch my video of the process below: