Four different stinging nettle-like plants are found in Florida, three of which belong to the genus Urtica. Stinging nettles have tiny hairs covering either all or certain parts of the plants that contain a toxic substance. When you touch the tiny stinging hairs, you'll experience a painful, stinging or burning sensation and often a reddish rash on your skin. Although all stinging nettle-like plants in Florida are considered herbs, they're also regarded as weeds.
Heart-Leaf Nettle (Urtica Chamaedryoides)
Also called the weak nettle or ortiguilla, the heart-leaf nettle is an annual herb with stinging hairs that's native to Florida. The multiple-stemmed plant grows upright but weak and can reach 20 inches in height. Its leaves are triangular to heart-shaped, ½- to 2-½ inches long and ½- to 1-½ inches wide, and arranged opposite one another in pairs along the branching stems. The leaves have coarse teeth on the edges. The heart-leaf nettle produces tiny greenish flowers in globe-shaped clusters in the leaf axils from spring until summer. You'll find this stinging nettle plant growing in rich soils in floodplains, woods, farm land and disturbed soils.
Stinging Nettle (Urtica Dioica)
The stinging nettle plant is similar to the heart-leaf nettle and is found in Florida, but it's native to Eurasia and is a perennial herb. The stinging nettle has oval-shaped leaves with pointed ends and jagged teeth along the edges. The leaves are arranged opposite each other along the stems with flowers in long compound clusters. The spiky, stinging spines are most noticeable on the leaves and stems.
Burning or Dwarf Nettle (Urtica Urens)
The burning nettle, also called the dwarf nettle, is also found in Florida but is native to Europe and blooms in elongated flower clusters. This annual herb also has coarsely lobed, oppositely arranged leaves with toothed margins, but its leaves are more deeply toothed than the stinging nettle (Urtica dioica). Also different are the flower spikes, which are shorter than the stinging nettle's flowers, and the leaf shape, which is more round. The sting of the burning nettle is milder than the other nettle plants.
Bull Nettle (Cnidoscolus Stimulosus)
Unrelated to the other Urtica species, the bull nettle also has stinging hairs and is found throughout Florida, thriving in dry, sandy soils along roads, as well as in abandoned fields, disturbed sites, pine forests and other wooded areas. The bull nettle has stout stems that branch out into a V-shape and grows up to 3 feet tall. The bull nettle's leaves are hand-shaped with three to five deep, toothed lobes and are alternately arranged along the stems. Also called the tread softly, stinging nettle and spurge nettle, the bull nettle produces white, star-shaped flowers, followed by spiny, globe-shaped or cylindrical seed capsules that contain dark-brown seeds. The capsules, stems and leaves are all covered in the spiny, toxic hairs.