I have dyed yarn with onion skins, though that was a long time ago. I am working on spinning enough alpaca yarn to make it worthwhile to try my hand at dying, but haven't got that far yet. I have been doing some research into the matter though.
Do you know what sort of plants you will need for the colors you want?
I haven't had the chance to try natural dyeing. Somewhere out in the shed I have a couple old books on dyeing. One actually has yarn swatch pictures to show what the different mordants did to the color on cotton and wool. I've been thinking about this since spring when the Scotch Broom bloomed, since I know the flowers and leaves are listed as a good dyes and there are so many of the invasive things here.
I remember seeing woad seeds available from LocalHarvest. Apparently it doesn't need a mordant to create a blue dye, it is an edible, easily grown annual in the brassicae family (wonder if it turns your tongue blue?) and you can use the stems in basket making. Sounds like a valuable plant.
The Woad Song
What's the use of wearing braces?
Spats and hats and boots with laces?
Vests and pants you buy in places
Down on Brompton Road?
What's the use of shirts of cotton?
Studs that always get forgotten?
These affairs are simply rotten,
Better far is woad.
Woad's the stuff to clothe men.
Woad to scare your foemen.
Boil it to a brilliant hue
And rub it on your back and your abdomen.
Ancient Britons never hit on
Anything as good as woad to fit on
Necks or knees or where you sit on.
Tailors be you blowed!!
2.
Romans came across the Channel
All wrapped up in tin and flannel
Half a pint of woad per man'll
Clothe us more than these.
Saxons used to waste their stitches
Building beds for bugs in britches
We have woad to clothe us which is
Not a nest for fleas
Romans keep your armours.
Saxons your pyjamas.
Hairy coats were meant for goats,
Gorillas, yaks, retriever dogs and llamas.
Tramp up Snowdon with your woad on,
Never mind if you get rained or snowed on
Never need a button sewed on.
Bottoms up to Woad!!