Yesterday I went down the allotment to harvest weeds.*
Specifically, I dug up a bunch of dandelion roots, and gathered a handful of what I suspected was (and now am sure is) chickweed. I've been reading this fantastic herbalism zine, which told me that both of these are medicinally useful.
Dandelion root can be used to stimulate the liver, gallbladder, and kidneys; or just as a general tonic containing lots of minerals (including iron, potassium, and calcium, all particularly useful if you're vegan). To preserve it, dry the roots (wash them and leave them somewhere dark; if you split larger roots down the middle they'll dry faster), and store them in a sealed container in a cool, dark place. To use it, make a decoction by putting 1oz of root and 1pt of water in a pan and simmering until the water has reduced by 50%. Strain and drink.
Chickweed is good as an infusion of dried herb for coughs and hoarseness; and as an infused oil to treat minor skin problems (burns, rashes, itching, dryness). Alternatively you can just eat the leaves as a salad leaf. I tried my sample plants after I'd IDed them, and found it quite tasty. To dry it, it's best to hang it somewhere dark and warm (but spread on a windowsill is fine if that's the easiest option for you). To make an infusion, pour boiling water over the dried herb, cover, and leave for 10-30 min. To make an infused oil, macerate the dried herb in olive oil, place in a warm sunny window for 2 weeks, strain, and bottle in a dark glass bottle. (You can make a stronger oil by adding more herbs and leaving for another fortnight.)
I can't yet report back on how these work (or taste!) as I'm still in the drying stage. I'll update in a couple of weeks.
The best bit about all of this is that these are not plants which I have any trouble at all in growing. Currently the chickweed is popping up all over the squash bed as the squash dies down. I'm incredibly pleased to find out that there's something useful (beyond just chucking it in the compost heap) that I can do with it.
Next task: try to establish whether any of my other weeds are useful. Sadly I'm not sure we have any yarrow.
* I planted some broad beans and early dwarf peas, as well -- we have an Aphid Problem which means that the only chance to get any actual broad beans is to get the plants up and producing in the spring before the aphids have woken up. Which in turn means overwintering them.