I gathered some Eucalyptus leaves during a recent visit to Corfu. Eucalyptus makes a wonderful dye, both from the leaves and the bark.
I dyed both wool and some cellulose fabrics (linen and cotton)

To make the dye, I used 50 grams of Eucalyptus leaves and put them into a dye pot filled with water.
I simmered the dyepot for +1 hour at 50 degrees Celsius.
I then added the mordanted wool and fabric samples to the dyepot.
I simmered the dyepot for +1 hour.
Then I turned off the heat and let the dyepot cool and left it overnight. I find that I get stronger colours when leaving the yarn to soak longer.

All cellulose fibres, yarns and fabrics must be scoured prior to mordanting or dyeing. Please see my previous article on how to do this.
How to Scour Linen

For these samples, I used several different linen and cotton fabrics as well as wool yarn.

Unbleached Cotton
Bleached Linen
Linen/Cotton Blend
Natural Linen (light weight)
Natural Linen (heavy weight)

Please look for my naturally dyed yarns in my Paivatar Yarn Shop on Etsy.

More about Naturally Dyed Yarns

Apple Leaf Dye
Madder Root Dye
Alkanet Root Dye
Brazilwood Dye
Himalayan Rhubarb Plant Dye

Natural Dye Books
Indigo from Seed to Dye
Indigo: Dye It, Make It: Techniques from plain and dip-dyeing to tie-dyeing and batik, in natural indigo blue
Wild Color, Revised and Updated Edition: The Complete Guide to Making and Using Natural Dyes
Natural Dyes
The Art and Craft of Natural Dyeing: Traditional Recipes for Modern Use
EBAY – NATURAL DYES
NATURAL DYES – US
NATURAL DYES – UK