The Shamanic Herbal: Thor's Herbs

(Thor seems to have more associated plants and trees than any other god, but then he is a patron of farmers, and one of the most popular gods of the peasantry.)

Garlic

(Allium sativum)
Names: Spear Leek, Ajo, Poor Man's Treacle, Stinkroot
Medicinal Uses: Eat whole cloves as a mild antibiotic to raise the immune system in the face of any bacterial or viral infection, to reduce cholesterol, and to regulate blood sugar for diabetics. Topically, rub on acne or skin infections.
Household Uses: Use in any savory cooking, in whatever amount you prefer. As the Galloping Gourmet was said to have intoned: "If you like garlic and your lover doesn't, get yourself another lover." Garlic heads can also be roasted whole and eaten out of their wrappings.
Traditional Magical Uses: The ultimate protective edible plant, garlic was carried and eaten to ward off diseases, thieves, foul weather, and any evil spirits one might run into.
Shamanic Magical Uses: Sacred to Thor, this plant protects against lightning, and is specifically a ward against the "unseelie" Alfar of Svartalfheim. Wearing it while there invokes Thor's protection (make sure that he doesn't have anything against you before trying this trick) and while they may not attack you, they won't like you much either, so keep your business short.

Hawthorn

(Crataegus oxacantha)
Names: Bread And Cheese Tree, Gaxels, Hagthorn, Halves, Haw, Huath, Ladies' Meat, May Tree, Mayblossom, Quickthorn
Medicinal Uses: Hawthorn berries improve cardian circulation, dilating the blood vessels and improving the pump action, which helps both high and low blood pressure.
Traditional Magical Uses: Protects against lightning and the dead. Hawthorn is used in love charms, especially where there is pain or unrequited love involved, and also to maintain chastity or fidelity. Traditional Maypoles had three rings on the top, and the highest and smallest was made of hawthorn. Some writings will tell you to climb to the top of a hawthorn tree to gather its wood; these folks have clearly never grown hawthorns. They don't grow very tall - more like a large shrub - and to attempt to climb even the tallest would be to incur grave injury from the thorns, if you didn't knock the whole thing over. Hawthorn is one of the traditional British "hedgerow" plants.
Shamanic Magical Uses: Supposedly Thor created the Hawthorn with a single bolt of lightning. It is one of the nine woods used in funeral pyres for the cremation of warriors. The Alfar love hawthorn, and it is a good propitiatory plant for them as well. Its thorns can be broken off and stabbed through something that you wish to harm or stop, or a symbol of your foe. If you are unsure of the whether such an action is ethical, ask for Thor's blessing and protection on your action. If he does not seem inclined to give it to you, perhaps you shouldn't do it.

Houseleek

(Sempervivum tectorum)
Names: Hen and Chicks, Thor's Beard, Sengren, Welcome-Home-Husband-Though-Never-So-Drunk (I particularly like that one, and I sometimes wonder if it was Sif who made that up!)
Medicinal Uses: Rather like a weak version of aloe vera, its petals can be cut open and the salve smeared on burns.
Traditional Magical Uses: Protects a house from lightning, especially when placed on the roof in a pot. Brings good luck. Sacred to Thor in his aspect as Hurler of Lightning.

Leek and Onion

[Leek] [Onion](Allium spp.)
Names: Oingnum, Onyoun, Unyoun, Yn-leac
Medicinal Uses: All alliums raise the immune system to one extent or another.
Household Uses: Cooking. Lots of it, especially if it's traditional northern food.
Traditional Magical Uses: Leeks are carried as protective amulets in battle, and are planted around the house to drive away evil. Onions have long been sliced and rubbed on the body to heal warts, disease and infections, thus transferring the sickness into the onion, which is thrown away. They have also been stuck with pins and used as protective charms.
Shamanic Magical Uses: Sacred to Thor, along with all the other Allium family, these can be offered as tribute or cooked and eaten to ask his blessing. Along with Garlic, you can feed them to people whose bodies need a thorough cleansing, of the lightning-bolt variety. These are also powerful protective plants for any kind of safety charm; call of Thor's aid when you empower it.

Oak

(Quercus spp.)
Names: Ac, Duir, Jove's Nuts, Juglans, Iron Wood
Medicinal Uses: Highly astringent, high in tannins. Bark extract used for facial astringent on dark skin only.
Household Uses: Strong tea of oak bark used for vegetable tanning of leather.
Traditional Magical Uses: Oak twigs and acorns are hung up in windows to keep away evil and lightning. Oak wood, in a stave, lends strength. Acorns are used for any magics involving good beginnings.
Shamanic Magical Uses: Oak is claimed by various different Norse deities. The most common is Thor, but it is also claimed by the giantess Angrboda, the wife of Loki, and Hag (or Hagia, Wise Woman) of the Iron Wood. The term "iron wood" was used to refer to the rot-resistant oak, and it can be used as a talisman to get to that place. It is the tree of the rune Ac.

Thistle

(Onopordium acanthium)
Names: Thrissill, Ass-wind [Tormentil]
Medicinal Uses: Juice is said to relieve skin infections; root is said to diminish mucous discharges.
Household Uses: Stems can be blanched, peeled, and served like asparagus. Flower disk can be boiled or steamed and then eaten like artichokes. Seeds can be pressed for a household oil.
Traditional Magical Uses: Often used as a curse plant, Thistle can also be used for protection. It is sacred to Thor, and can be used to invoke his wrath when those he watches over have been wronged.

Tormentil

(Potentilla erecta)
Names: Thormantle, Biscuits, Earthbank, Ewe Daisy, Flesh And Blood, Septfoil, Shepherd's Knot
Medicinal Uses: Highly astringent, high in tannins. Root used to reduce bowel inflammation associated with diarrhea.
Traditional Magical Uses: Used to invoke Thor's protection and for male sexual potency. Those who work with spirit-possession drink the tea to prevent against unwanted spirit invasions. The root is hung up in the home to keep away evil.
Shamanic Magical Use: Root carved with rune of Thor's name can be used to take one to his hall Bilskrudnir, but only if one has prior permission to be in Asgard.