When the sharp, pointed hairs penetrate skin, they break off releasing an irritating fluid, which consists of many chemicals.  This was originally thought to be formic acid, similar to what ants emit, but recent research has revealed it to be three main chemicals—a histamine to irritate the skin, acetylcholine to bring on a burning sensation, and hydroxytryptamine to encourage the other two (Elliott 1997).  The affected skin is left with a small rash that can last for hours or even days.  The severity depends on the part of the body affected, the length of the contact, the size of the plant and the individual response.   The hairs are generally on the underside of the leaves and on the stem.  The genus name Urtica comes from the Latin verb urere, meaning ‘to burn,’ because of these stinging hairs.  The species name dioica means ‘two houses’ because the plant usually contains either male or female flowers (Taylor 1998), which are either on different branches or different plants altogether.

Nettle reproduces vegetatively and by seeds.  Nettle produces abundant seed.  Plants growing in the shade produce approximately 500 to 5,000 seeds per shoot and plants growing in full sunlight produce 10,000 to 20,000 seeds per shoot (Carey 1995).  Seeds remain on the plant until frost when they fall to the ground.  Seeds are not dormant and can germinate 5 to 10 days after maturity (Carey 1995).

Distribution Map: Urtica dioica

A normal habitat for the nettle is stream banks, the borders of deciduous woodlands, moist sites along streams, on mountain slopes, in woodland clearings, and in disturbed areas.  Which happens to be pretty much everywhere.   Nettle tends to be found in temperate and tropical wasteland areas around the world, many countries have a variety of the plant.   The order Urticales has subdivided itself into six families: Moraceae- the mulberry family, Urticaceae- the nettle family, Cecropiaceae- the cercropia family, Ulmaceae- the elm family, Cannabaceae- the hemp family, and Barbeyaceae.   The Urticaceae family has about 40 genera with 500 species.  These tend to be in America, Asia, Africa and Europe.  The Urtica genus has about 30 species which occur in Europe and North America (Gibbs 1950).   The nettle is native to Eurasia and said to have been brought to North America by English settlers.  Even though the common nettle is now highly known for being in mild and moist soils, they are often found in association with human settlements (Godwin 1956).  So where they might have started in Eurasia, nettles followed humans as we migrated across the world.  Urtica dioica are found nearly everywhere in the United States staying closer to the coasts, but going as far south as Kentucky.  Nettles are less likely to be found in the south.  In the Bay Area there are three native species and two known European species.   Records have shown the Urtica dioica to have been present in interglacials of three different ages, the full-glacial, the late-glacial, and the post-glacial (Godwin 1956).   It has a high altitudinal and latitudinal range in conformity with the likelihood that it was a full-glacial survivor.  Nettle generally grows on deep, rich soils ranging from sea level to 10,000 feet (3,000 m) (Jepson).

The nettle is able to survive through just about anything, however persistent flooding and mowing will kill it.  Nettles occur and produce seed in shady habitats but produces more seed in the full sun.  They love the warmth, but will take the cold.  Seeds will remain on the plant until frost when they fall to ground.  They are not dormant and will germinate five to ten days after its maturity (Carey 1995).   In short the nettle is a weed and will almost never go away.    

    Once you encounter a nettle you will never forget it.  I remember the first time I was 12, I think, and I was in Germany visiting relatives with my mom and brother.  We were waiting to cross the street and I saw that there was this green plant to the right of me, but I didn’t think very much of it.  Until the light turned green and I somehow extended my arm right into it.  As soon as I touched the plant, I quickly brought my arm in and inspected it.  My arm was red and had small bumps.  It didn’t exactly hurt; I was more confused than anything.  I did have a burning sensation and I quickly brought it to my mom’s attention.  She told me about the plant and then got something to cool it. 

 My next encounter was when I was 16, also in Germany, and I was hanging out with my aunt and her husband.  Well for some reason I was riding a tandem bicycle with her husband and I remember getting really annoyed with him.  I was thinking that I would do anything to get out of this situation and go home, or go shopping.  When we stopped to take a break I saw a nettle plant near the trail.  I think I pretended to do some sort of stretch when I just stuck my whole arm into the plant.  My arm was red and surprisingly it still didn’t really hurt, it was more irritating.  I complained about it hurt and how I should go and tend to it.  I really just freaked out on him and left.  From that incident stemmed a long running joke with my brother and how I would love to just have nettle around me for situations just like those.

**  In the Hans Christian Anderson story, "The Wild Swans," the 11 brothers of a beautiful princess were trapped by an evil spell in the bodies of swans. The spell could only be broken if the princess made each brother a coat from nettles and didn’t utter a word the whole time she was doing it. As one might expect, she succeeded. **

Last nettle note: Urtica is apparently also very efficient in the filtering of metals, minerals and waste materials from contaminated water, storing these substances in its plant fibers and cleansing water supplies. It's excellent for organic waste treatment and as a detoxification system. Many of the materials it collects can be recovered afterward from the dead plant matter.  It's great for composts.