Picking and using horsetail.
Horsetail (Equisetum arvense) is best picked early in the season: it's nice and soft then, and can be infused for ready use.
As summer progresses the green summer shoots of horsetail get harder and harder, and if you pick your horsetail late in summer it requires decoction.
Do label your pickings so you know when they were picked.
We only use the one horsetail in Finland; all the others are considered toxic. Not that they are, if you look at the use of horsetails in other countries: for instance, they use any and all of them in the US. And not that they are, if you look at actual hospitalizations: Equisetum is not even mentioned in a toxic plants book I own, where the authors looked at German hospital records ("Giftpflanzen in Natur und Garten", Buff + v.d. Dunk, 1988).
But we know that marsh horsetail (Equisetum palustre) does contain small amounts of nicotine. Not much, but enough to label it "toxic" over here, and enough to necessitate the teaching of the differences between the two species, over here. There are differences, even in the green summer shoots which look confusingly alike.
All horsetails are toxic when growing in extremely rich soil, like the ditch off a pigsty. Don't pick them there. Find more normal circumstances and pick your horsetails there instead.
Uses, well, it's diuretic, but where it shines is in helping to heal broken bones. Horsetail contains loads of silica, which makes nice grids for calcium to adhere to: faster healing of bones. Add calendula or plantain (Plantago spp.) to your tea for a nicely rounded bone-healer.
Horsetail contains loads of other minerals and trace elements, and it's a good choice for a mineral herb when you're convalescent. Like after a major flu or after an operation. Or when you're mending broken bones.
The minerals etc. are best absorbed in teas.
Infusion (early summer pickings): 1 teaspoon dried or fresh herb to 2 dl boiling water, let sit for 10 or so minutes, strain.
Decoction (late summer pickings): 1 teaspoon dried or fresh herb to 2.5 dl cold water, bring to a boil, let boil for a while, let cool to drinkable, strain.
Drink 2-3 cups a day for a week or two, or until the cast is off if you're healing bones. Either tea should be drunk within an hour of making it for maximum mineral absorption. Don't drink it late at night: it is a diuretic.
Minerals are also nicely absorbed in vinegars. Make a herbal vinegar and take 1 tea- or tablespoon 2-3 times a day in a glassful of water, or use in your salad dressings.
A tincture of mineral-rich herbs is a waste of both herb and alcohol - that is, if you're after the minerals.
Related entry: Getting rid of horsetail.