Urtica dioica

Scientific Name Urtica dioica L.
Synonyms Urtica dioica spp. gracilis, Urtica gracilis, Urtica procera, Urtica viridis
Common Names English: Stinging nettle, tall nettle, California nettle, slender nettle; German: Große Brennessel; French: Grande ortie ; Spanish: Ortiga menor, marrachincha; Portuguese: urtiga vermelha
Description Erect, herbaceous perennial with an extensive underground network of rhizomes (horizontal underground stems) that can spread 150 cm (59.05 inch) or more in a season. Fibrous roots are produced along the rhizomes.

Descriptions

Characteristic Features

A perennial plant with rhizomes, lanceolate leaves with toothed margins, erect usually unbranched stems, and fairly long 'stinging' hairs.

Young Plant

Cotyledons are oval, with a notch at the tip. The first leaves are opposite, oval to egg-shaped, thin and bright green. The toothed margins of the first few leaves are more rounded than in older plants. Young leaves and stems are covered with hairs and a few stinging hairs.

Cotyledons

Oval, with a notch at the tip.

Stems

Stems are mostly unbranched, and grow 90 - 200 cm (2.95 - 6.56 ft) tall (sometimes up to 270 cm; 8.85 ft). They are covered with bristly stinging hairs (fewer in the upper part of the stem), and otherwise, are smooth or have a few soft hairs. Stems are slender and approximately square in cross section.

Leaves

The thin, bright to dark green leaves are positioned opposite, with saw-toothed margins and infamous stinging hairs on the underside. Leaves are broadly to narrowly egg-shaped, 5 - 15 cm long, 2.5 - 5 cm wide (1.97 -5.9 inch long, 0.59 - 1.97 inch wide), with a rounded or heart-shaped base and a pointed tip. Aside from the stinging hairs, the upper and lower leaf surfaces are usually smooth (the lower surface may be slightly hairy). Pointed stipules (small leaf-like appendages) occur at the base of the leaf, but senesce early. Leaf stalks are 1/4 to 2/3 the length of the leaf.

Propagatio Organs

Flowers

Tiny, greenish-white flowers are arranged in clusters on slender, branched spikes formed in the leaf axils (usually 4 spikes per node). Male and female flower clusters are produced on the same plant (monoecious), but usually from different leaf axils. Male flower spikes are longer than female flower spikes.

Flowering Period

May-October.

Fruit

Stinging nettle produces a small, dry, oval-shaped, 1-seeded fruit (achene) that is yellow to grayish-tan. Fruits are clustered along drooping flower spikes.

Seeds

Germination occurs at alternating temperatures of 25ºC (77ºF) and 15ºC (59 ºF) following warm stratification and in the presence of light.

Viability Of Seeds

Abundant seeds are produced, most are short lived but some viable seeds remain in cultivated soil for up to 5 years.

Propagation

Vegetatively and by seeds.

Occurrence

Habitat

Pastures, nurseries, orchards, neglected yards, waste places, roadsides, flood plains, stream banks and ditches.

Soil

Moist, nitrogen-rich areas. The rhizomes have difficulty penetrating compacted soil. U. dioica prefers open textured soils of pH 5.0 to 8.0.

Additional Crop Information

Field crops, oat, barley, rye.

Agricultural Importance

The weediness of Urtica dioica is attributed to its spread by rhizomes, allowing it to form dense colonies that exclude other species by suppression. Stinging hairs on the stem and leaves of stinging nettle cause irritation upon contact with skin. They contain acetylcholine and histamine. Stinging nettle is a nitrophilic weed and an important alternative host of carrot fly. U. dioica is used as medicinal plant. Leaf extracts are considered to cure tuberculosis and rheumatism. They also can be a component in anti-dandruff shampoo.

Control

Integrated Crop Management

Eradication of an established colony is difficult because the subterranean system expands yearly and cannot be suppressed by mowing. This species does not compete well with grasses, but is able to establish and spread among legumes or other forbs. Stands of stinging nettle are thought to persist for 50 years. Distribution of this species is limited by its intolerance of poor fertility, dense shade and frequent disturbance. Some control may be obtained through repeated tillage and repeated cultivation over several years.

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