Here is a List of some basic Herbs & There Medical Value.
Poppy seeds - used to numb pain
Cobwebs - used to stop bleeding
Feverfew - used to cool feverish cats and treat head pain
Borage leaves - used to treat fevers
Marigold - used to treat infection and heal wounds and sores
Horsetail - used to treat infected wounds
Burdock root - used to treat infections, especially rat bites
Chervil (root) - used to treat infections
Wild garlic - rolling in this can help to keep out infection
Coltsfoot - used to treat kittencough
Catnip - used to treat blackcough, whitecough, and greencough, and can help to relax a cat
Chickweed - used to help treat greencough
Tansy - used to treat coughs
Thyme - used to calm a cat
Camomile - used to calm a cat
Juniper berries - used to treat bellyache
Chervil - used to treat bellyache
Water mint - used to treat bellyache
Daisy leaves - used to treat aching joints
Comfrey - used to treat broken bones
Nettle leaves - used to treat swelling
Celadine - used to treat ailments of the eyes
Snakeroot - used to counter poison
Honey - used to treat sore throats
Mouse bile - used to remove parasites from a cat's coat
Dock leaves - used to make a cat's coat slippery
Yarrow - used to make a cat vomit and expel poisons from the body
Deathberries (yew) - of no medicinal value; bright scarlet berries that can kill a cat if they are not expelled quickly enough
Nightshade - of no medicinal value; much the same as yew
NOTE: Please do not use these in real life. These plants are only used in the books. Please consult a doctor if any of the above happen. Also, I Did not Type This, and i take no Credit for it:3