Taraxacum

Taraxacum, a genus within the Asteraceae family, is better known as dandelions. These plants are found nearly everywhere on Earth, missing only from tropical and polar regions. Two of the most widespread species, the common dandelion (T. officinale) and the red-seeded dandelion (T. erythrospermum), originally came from Europe and were brought to North America, where they are not native. Dandelions do well in temperate climates, turning up in lawns, gardens, roadsides, farm fields, and many other spots. Because they are abundant and adaptable generalists, they serve as a crucial early spring food source for many pollinators. The scientific and hobbyist study of this genus is called taraxacology.

The name Taraxacum comes from the Arabic *tarakhshaqūn*, meaning "bitter herb," which may have Persian roots. The Persian scholar Al-Razi used this word for dandelions, chicory, and endives, noting that "the tarakhshaqūn is like chicory, but more efficacious," though it is unclear which plant he meant. If Persian, the word could combine *talk* ("bitter") and *chakūk* ("purslane"). Gerard of Cremona, translating Arabic into Latin around 1170, spelled it *tarasacon*. The English name "dandelion" comes from the French *dent de lion* ("lion's tooth"), referring to the jagged leaves. Other common names include blowball, cankerwort, doon-head-clock, witch's gowan, milk witch, lion's-tooth, yellow-gowan, Irish daisy, monks-head, priest's-crown, puff-ball, faceclock, pee-a-bed, wet-a-bed, swine's snout, white endive, and wild endive. The folk name "piss-a-bed" (and French *pissenlit*) points to the leaves' strong diuretic effect. In Swedish, it is called *maskros* ("worm rose"), after the thrip nymphs often found on the plant.

Taraxacum species are tap-rooted, perennial herbs native to temperate areas of the Northern Hemisphere. Many species reproduce by apomixis (asexual seed production), which creates many local populations and endemism. In the British Isles alone, 234 microspecies (morphologically distinct clones) are recognized within nine loosely defined sections. Some dandelions act as ruderals, quickly colonizing disturbed soil. The common dandelion has spread across much of the temperate world, especially along roads, in cemeteries, lawns, and pastures. A week or two after flowering, the flower head turns into a round seed head. The bracts (specialized leaves around the flower) curve backward, the yellow petals fall away, and the parachute ball opens fully. Mature seeds attach to white, fluffy parachutes that detach easily and glide on the wind.

Leaves are 5–25 cm long or longer, simple, lobed to pinnatisect, forming a basal rosette above the central taproot. Flower heads range from yellow to orange, opening in sunlight or on warmer days and closing at night. They sit atop a hollow, leafless stem (scape) that rises 1–10 cm or more above ground. Stems and leaves ooze a white, milky latex when broken. A rosette can produce several flowering stems at once. Each flower head is 2–5 cm across and consists entirely of ray florets. Heads mature into spherical seed heads (blowballs or clocks) containing many single-seeded fruits called cypselae, similar to achenes. Each cypsela has a pappus of fine hairs that aids wind dispersal. The pappus's unique shape creates a vortex ring that stays attached to the seed, helping it travel far. It can also adjust its form based on air moisture, closing up to reduce separation from the stem until conditions are right for dispersal and germination.

In Taraxacum ovules, only the megaspore mother cell enters meiosis. *T. officinale* can reproduce sexually through meiosis and haploid gametes, or asexually through parthenogenetic apomixis, which produces diploid seeds identical to the mother plant. This parthenogenesis lets an unreduced egg cell develop into an embryo without fertilization. Dandelion flowers contain various phytochemicals, including polyphenols like apigenin, isoquercitrin, and caffeic acid, as well as terpenoids, triterpenes, and sesquiterpenes. The roots hold a lot of the prebiotic fiber inulin. Dandelion greens contain lutein. Taraxalisin, a serine proteinase, is found in the latex of the roots, with peak activity in April, at the start of the plant's growth.