Stinging nettles, Urtica dioica and the annual Urtica urens, friend or foe?
Of course it all depends on your view, but as far as the French are concerned they're very much on side.
Being rich in nitrogen, magnesium, potassium, oligoelements, encymes, and trace minerals, they are held in such high regard that there is even a society devoted to them, the Association des Amis d'Ortie!
Purin d'ortie is liquid nettle manure. A wholly natural fertiliser which is popular even with non organic gardeners. A simple concoction which can be used as a drench or a foliar feed, I count myself lucky that I have nettles in abundance growing on waste ground near the river at the back of Le Banquet. A true compost mine
Making the 'brew' is a simple affair. I literally take the sheers out back and chop as many nettle tops as I can stuff into a large tub, fill it with water and let it ferment for anything up to two weeks. Once the bubbles stop rising to the top, it's ready. Be warned though, this stuff stinks, it really smells, think silage, so it's sensible if the tub has a lid.
To use it as a drench, I dilute it to about ten percent. For a foliar spray, a weaker solution is effective and easily absorbed.
Horsetail, Equisetum arvense, is also commonly used to make a similar preparation and indeed just about all weeds can be 'drowned' in this way and the resulting sludge chucked on the compost heap as an activator, nothing is more satisying than putting annoying perennial and annual weeds to good use.