Foray into natural dyes. in Tales from the kitchen witch

I want to try my hand at natural dyes. Just for funsies.
To start im reading about marigold as a natural dye to dye fiber a sunshiney yellow tone.

it says to harvest marigolds at its peak of health. Dry till ready to use.
Mix alum ( a mordant) to your water, then simmer your flowers and wool in the same pot till the dye extracts.
Sounds easy enough right?
going to try this tomorrow. I bet if i can use the marigolds dried. I can use them fresh too!