A Cape Town Lion’s Head tagged image from photographer – Feggy Art as published on Flickr.
Dandelion Close-Up
Image by Feggy Art
Taraxacum is a large genus of flowering plants in the family Asteraceae. They are native to Eurasia and North America, and two species, T. officinale and T. erythrospermum, are found as weeds worldwide. Both species are edible in their entirety. The common name dandelion (pronounced /ˈdændɨlaɪ.ən/ DAN-di-ly-ən, from French dent-de-lion, meaning lion’s tooth) is given to members of the genus, and like other members of the Asteraceae family, they have very small flowers collected together into a composite flower head. Each single flower in a head is called a floret. Many Taraxacum species produce seeds asexually by apomixis, where the seeds are produced without pollination, resulting in offspring that are genetically identical to the parent plant.
The species of Taraxacum are tap-rooted biennial or perennial herbaceous plants, native to temperate areas of the Old World.
The leaves are 5–25 cm long or longer, simple and basal, entire or lobed, forming a rosette above the central taproot. The flower heads are yellow to orange colored, and are open in the daytime but closed at night. The heads are borne singly on a hollow stem (scape) that rises 1–10 cm or more above the leaves and exudes a milky sap (latex) when broken. A rosette may produce several flowering stems at a time. The flower heads are 2–5 cm in diameter and consist entirely of ray florets. The flower heads mature into spherical ‘clocks’ containing many single-seeded fruits called achenes. Each achene is attached to a pappus of fine hairs, which enable wind-aided dispersal over long distances.
The flower head is surrounded by bracts (sometimes mistakenly called sepals) in two series. The inner bracts are erect until the seeds mature, then flex downward to allow the seeds to disperse; the outer bracts are always reflexed downward. Some species drop the ‘parachute’ from the achenes; the hair-like parachutes are called pappus, and they are modified sepals. Between the pappus and the achene, there is a stalk called a beak, which elongates as the fruit matures. The beak breaks off from the achene quite easily, separating the seed from the parachute.
A number of species of Taraxacum are seed dispersed ruderals that rapidly colonize disturbed soil, especially the Common dandelion (T. officinale), which has been introduced over much of the temperate world. After flowering is finished, the dandelion flower head dries out for a day or two. The dried petals and stamens drop off, the bracts reflex (curve backwards), and the parachute ball opens into a full sphere. Finally, the seed-bearing parachutes expand and lift out of it. The parachute drops off the achene when it strikes an obstacleAfter the seed is released, the parachutes lose their feathered structure and take on a fuzzy, cotton-like appearance, often called ‘dandelion snow’
Reproduced from Wikipedia under the Creative Commons License.
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