"Nettles are so well known, that they need no description; they may be found by feeling, in the darkest night."
Hopefully, you won't stumble on Nettles at night. Or during the day. It is worth learning to identify nettles by sight so that you can avoid accidental contact with the plant. Parents especially should learn so that they can teach their childern. The stinging of Nettles is usually not immediate and for this reason they can be diffictult to learn. If you brush up against them while walking along a path or pushing through a thicket you might be well away from the plants by the time you notice the stinging. In order to harvest them you may want to use scissors, which can be done in such a way as to avoid touching the plant. Gloves can be helpful, but often the Nettles will sting through thin or light material. With callouses you may not need gloves at all. Except for in sensitive individuals, the stinging property of Nettle breaks down with cooking or drying. Nettle is a favorite green vegetable and nourishing herbal tisane.
Here are some images from April: http://www.nathanielwhitmore.com/blog/nettles
"This is also an herb Mars claims dominion over. You know Mars is hot and dry, and you know that Winter is cold amd moist; then you may know as well the reason why Nettle-tops eaten in the Spring consume the phlegmatic superfluities in the body of man, that the coldness and moistness of Winter hath left behind... ...to open the pipes and passages of the lungs... ...helps the swelling of the almonds of the throat... ...to heal and temper the inflammations and soreness of the mouth and throat... ...to provoke women's courses... ...against the stinging of venemous creatures... ...The seeds or leaves bruised, and pu tinto the nostrils, stays the bleedign of them, and takes away the fresh growing in them called polyps... ...aches and gouts, and the defluxation of humours upon the joints or sinews..."
Quick description of a medicinal soup: http://www.nathanielwhitmore.com/blog/nettle-chive-soba-soup