24 Mei 2010

Verbascum thapsus

Verbascum thapsus (Great or Common Mullein) is a species of mullein native to Europe, northern Africa and Asia, and introduced in the Americas and Australia.

It is a hairy biennial plant that can grow to 2 m or more tall. Its small yellow flowers are densely grouped on a tall stem, which bolts from a large rosette of leaves. It grows in a wide variety of habitats, but prefers well-lit disturbed soils, where it can appear soon after the ground receives light, from long-lived seeds that persist in the soil seed bank.

It is a common weedy plant that spreads by prolifically producing seeds, but rarely becomes aggressively invasive, since its seed require open ground to germinate. It is a very minor problem for most agricultural crops, since it is not a very competitive species, being intolerant of shade from other plants and unable to survive tilling.

It also hosts many insects, some of which can be harmful to other plants. Although individuals are easy to remove by hand, populations are difficult to eliminate permanently.

It is widely used for herbal remedies with emollient and astringent properties. It is especially recommended for coughs and related problems, but also used in topical applications against a variety of skin problems. The plant was also used to make dyes and torches.

Verbascum thapsus is a dicotyledonous plant that produces a rosette of leaves in its first year of growth.The leaves are large, up to 50 cm long. The second year plants normally produce a single unbranched stem usually 1–2 m tall.

In the East of its range in China, it is, however, only reported to grow up to 1.5 m tall. The tall pole-like stems end in a dense spike of flowers that can occupy up to half the stem length.

All parts of the plants are covered with star-shaped trichomes. This cover is particularly thick on the leaves, giving them a silvery appearance. The species' chromosome number is 2n = 36.

Flowers are pentamerous with five stamen that are fused to the petals, a 5-lobed calyx tube and a 5-petalled corolla, the latter bright yellow and an 1.5–3 cm (0.5–1 inch) wide. The flowers are almost sessile, with very short pedicels (2 mm, 0.08 in).

The five stamens are of two types, with the three upper stamens being shorter, their filaments covered by yellow or whitish hairs, and having smaller anthers, while the lower two stamens have glabrous filaments and larger anthers.

The plant produces small ovoid (6 mm, 0.24 in) capsules that split open by way of two valves, each capsule containing large numbers of minute brown seeds less than a millimetre (0.04 in) in size, marked with longitudinal ridges. A white-flowered form, V. thapsus f. candicans, is known to occur.

Flowering lasts for up to three months from early to late summer (June to August in northern Europe), with flowering starting at the bottom of the spike and progressing irregularly upward; each flower opens for part of a day and only a few open at the same time around the stem.

Source: http://en.wikipedia.org/wiki/Verbascum_thapsus

See Also: flowers brisbane, flower sydney, flowers philippines, flowers jamaica

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