Urtica dioica in the context of Contact dermatitis

Bast fibre (also called phloem fibre or skin fibre) is plant fibre collected from the phloem (the "inner bark", sometimes called "skin") or bast surrounding the stem of certain dicotyledonous plants. Some of the economically important bast fibres are obtained from herbs cultivated in agriculture, for instance flax, hemp, or ramie, but bast fibres from wild plants, such as stinging nettle, and trees such as lime or linden, willow, oak, wisteria, and mulberry have also been used. Bast fibres are soft and flexible, as opposed to leaf fibres from monocotyledonous plants, which are hard and stiff.

Since the valuable fibres are located in the phloem, they must often be separated from the woody core, the xylem, and sometimes also from the epidermis. The process for this is retting, and can be performed by micro-organisms either on land (nowadays the most important) or in water, or by chemicals (for instance high pH and chelating agents), or by pectinolytic enzymes. In the phloem, bast fibres occur in bundles that are glued together by pectin and calcium ions. More intense retting separates the fibre bundles into elementary fibres, which can be several centimetres long. Often bast fibres have higher tensile strength than other kinds, and are used in high-quality textiles (sometimes in blends with cotton or synthetic fibres), ropes, yarn, paper, composite materials and burlap. An important property of bast fibres is that they contain a special structure, the fibre node, that represents a weak point, and gives flexibility. Seed hairs, such as cotton, do not have nodes.

Chrysaora fuscescens, the Pacific sea nettle or West Coast sea nettle, is a widespread planktonic scyphozoan cnidarian—or medusa, "jellyfish" or "jelly"—that lives in the northeastern Pacific Ocean, in temperate to cooler waters off of British Columbia and the West Coast of the United States, ranging south to Mexico. The Pacific sea nettle earned its common name in-reference to its defensive, 'nettle'-like sting; much like the stinging nettle plant (Urtica dioica), the sea nettle's defensive sting is often irritating (possibly mildly painful) to humans, though rarely dangerous.

The Pacific sea nettle has a distinctive, golden-brown bell—the main functioning 'body' or 'head' of a jelly—with a reddish tint. The bell can grow to be larger than one meter (3’) in diameter in the wild; however, most are less than 50 cm across. The long and spiraling, whitish oral arms (and 24 undulating, maroon tentacles) may trail behind the nettle as far as 15 feet (4.6 m).

Seventeen elements or nutrients are essential for plant growth and reproduction. They are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), iron (Fe), boron (B), manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo), nickel (Ni) and chlorine (Cl). Nutrients required for plants to complete their life cycle are considered essential nutrients. Nutrients that enhance the growth of plants but are not necessary to complete the plant's life cycle are considered non-essential, although some of them, such as silicon (Si), have been shown to improve nutrient availability, hence the use of stinging nettle and horsetail (both silica-rich) macerations in biodynamic agriculture. With the exception of carbon, hydrogen and oxygen, which are supplied by carbon dioxide and water, and nitrogen, provided through nitrogen fixation, the nutrients derive originally from the mineral component of the soil. The law of the minimum expresses that when the available form of a nutrient is not in enough proportion in the soil solution, then other nutrients cannot be taken up at an optimum rate by a plant. A particular nutrient ratio of the soil solution is thus mandatory for optimizing plant growth, a value which might differ from nutrient ratios calculated from plant composition.

Plant uptake of nutrients can only proceed when they are present in a plant-available form. In most situations, nutrients are absorbed in an ionic form by diffusion or absorption of the soil water. Although minerals are the origin of most nutrients, and the bulk of most nutrient elements in the soil is held in crystalline form within primary and secondary minerals, they weather too slowly to support rapid plant growth. For example, the application of finely ground minerals, feldspar and apatite, to soil seldom provides the necessary amounts of potassium and phosphorus at a rate sufficient for good plant growth, as most of the nutrients remain bound in the crystals of those minerals.

CR gas or dibenzoxazepine (chemical name dibenz[b,f][1,4]oxazepine, is an incapacitating agent and a lachrymatory agent. CR was developed by the British Ministry of Defence as a riot control agent in the late 1950s and early 1960s. A report from the Porton Down laboratories described exposure as "like being thrown blindfolded into a bed of stinging nettles", and it earned the nickname "firegas".

In its effects, CR gas is very similar to CS gas (o-chlorobenzylidene malononitrile), but twice as potent, even though there is little structural resemblance between the two. For example, 2 mg of dry CR causes skin redness in 10 min, 5 mg causes burning and erythremia, and 20 mg‍—‍strong pain. Water usually amplifies the pain effect of CR on skin. CR aerosols cause irritation at concentrations of 0.2 mcg/L, becoming intolerable at 3 mcg/L. The LD₅₀ of CR through air inhalation 350 mg·min/L.

Pioneer species are resilient species that are the first to colonize barren environments, or to repopulate disrupted biodiverse steady-state ecosystems as part of ecological succession. Various kinds of events can create good conditions for pioneers, including disruption by natural disasters, such as wildfire, flood, mudslide, lava flow or a climate-related extinction event, or by anthropogenic habitat destruction, such as through land clearance for agriculture or construction or industrial damage. Pioneer species play an important role in creating soil in primary succession, and stabilizing soil and nutrients in secondary succession.

Because pioneer species quickly occupy disrupted spaces, they are sometimes treated as weeds or nuisance wildlife by humans, such as the common dandelion or stinging nettle. Even though humans have mixed relationships with these plants, these species tend to help improve the ecosystem because they can break up compacted soils and accumulate nutrients that help with a transition back to a more mature ecosystem. In human-managed ecological restoration or agroforestry, trees and herbaceous pioneers can be used to restore soil qualities and provide shelter for slower growing or more demanding plants. Some systems use introduced species to restore the ecosystem, or for environmental remediation. The durability of pioneer species can also make them potential invasive species.

Urtica is a genus of flowering plants in the family Urticaceae. Many species have stinging hairs and may be called nettles or stinging nettles (the latter name applying particularly to U. dioica). The generic name Urtica derives from the Latin for 'sting'.

Due to the stinging hairs, Urtica are rarely eaten by herbivores, but provide shelter for insects. The fiber has historically been used by humans, and cooking preparations exist.