Stinging nettle (Urtica dioica), also known simply as nettle, grows in moist, shady environments throughout North America. An herbaceous perennial, hardy in U.S. Department of Agriculture plant hardiness zones 2 through 9, stinging nettle is collected for both food and home remedies, sold in tea form at supermarkets and avoided by those on outdoor excursions. The stinging sensation from the hairs that grow along the stem and undersides of the leaves is one way to confirm its identity, which fortunately causes only temporary discomfort; however, dogs have died from heavy exposure. Fortunately, there are numerous visual characteristics that help to identify stinging nettles in spring when it forms a lush carpet on the ground wherever it grows.
Stinging nettles, dormant in winter, regrow every spring from a network of underground rhizomes. In early spring, the dead stalks from the previous year's growth may still be present when new leaves emerge from the ground. The plants grow rapidly throughout spring as the weather warms, eventually reaching 3 to 6 feet in height by early summer. Their size in spring depends on how long it has been since they broke dormancy and began to grow.
Stinging nettles grow as single stalks, which may branch slightly at the top, though this does not usually occur until summer. Typically a vast network of underground rhizomes support dense colonies consisting of hundreds of individual stalks. The stalks can be widely spaced, but are more often concentrated in patches that form a vibrant green, ground cover in spring.
Stinging nettle leaves grow opposite each other along the stalks, with every leaf pair being perpendicular in orientation from the ones above and below. The leaves have serrated margins and are oval or spade-shaped in spring, though they often develop into heart shapes as the plants mature. When they emerge in spring, the first leaves may be only 1-inch wide and 2 inches long, although the leaves that form lower on the stalk as it rises from the ground are larger, measuring up to 2 inches wide and 6 inches long. The young leaves are covered in hairs on both sides, but the stinging hairs are concentrated on the undersides.
Stinging nettles grow in moist woods and disturbed soils, such as roadside ditches and wet places in lawns and pastures. They prefer rich bottomland soils, however, and grow most abundantly in riparian areas and flood plains. Partial to full shade is a common denominator in all the habitats where stinging nettles are found, though the plant can tolerate full sun in cooler climates.
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