Fire burn, and caldron bubble.
Before modern medicine, remedies for various hair and scalp treatments sounded a bit like the witch's brew in Macbeth. Here is a hair tonic recipe for dandruff published in a 19th century German newspaper, which my grandmother clipped and pasted in her scrapbook (it would seem dandruff runs in the family):
Hair tonic: A proven remedy for dandruff is burdock root. Take a handful of burdock root, place it in a container and pour a cup of water and as much mild vinegar over it. Let this stand for a few days. Then rub the scalp with the liquid several times a week until the flaking is gone. Or, grease the scalp with burdock root oil, found in any drugstore.
Starting in the 20th century, our culture has been overrun by shampoos and conditioners. Now there is a growing No 'Poo movement (yes, it even has its own entry on Wikipedia), which seems like a new thing, but is actually a return to days of yore. When I was just a young whippersnapper, I remember mom rinsing my hair with vinegar. Can't say I liked it all that much, but it worked.
The recommended recipe for washing hair is a tablespoon of baking soda in a cup of warm water. For rinsing, 1-2 tablespoons of apple cidar vinegar in a cup of water. (And then rinse that with cold water -- otherwise your hair might smell like pickles.)
At Info: Shampoo Free, I found this list of time-honored Hair Herbs:
What kind of herbs can I use to improve my hair's health?
Burdock: root helps prevent dandruff
Catmint: leaves encourage hair growth and soothes scalp irritations
Chamomile: flowers soften and lighten hair
Flannel Mullein: lightens hair
Goosegrass: tonic and cleansing, helps prevent dandruff
Henna: red hair dye and conditioner
Horsetail: non-fertile stems and branches strengthens the hair
Lavender: antiseptic, antibiotic, stimulates hair growth, and degreases
Lime: flowers clean and softens
Marigold: lightens hair color
Nasturtium: for hair growth
Parsley: enriches hair color and gives a nice luster
Rosemary: tonic and conditioner, one of the best herbs to use, gives luster and body, also slightly darkens the hair. (This is good to use if you notice your hair lightening due to baking soda use.)
Rhubarb: the root makes a yellow hair dye
Sage: tonic and conditioning, darkens the hair
Southernwood: encourages hair growth and helps prevent dandruff
Stinging Nettle: tonic and conditioning and helps prevent dandruff
Witch Hazel: leaves and bark are astringent and cleanses oily hair
And at Hubpages, 10 Natural Hair Remedies Your Locks Will Love