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What is Onosma?

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  • Written By: Terrie Brockmann
  • Edited By: Melissa Wiley
  • Last Modified Date: 30 August 2016
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The Onosma genus of plants contains about 150 species and belongs to the Boraginaceae, or borage, family. These perennials or biennials bear pretty little tubular flowers that may be white, yellow, pink, or red. Gardeners usually raise them for their blooms. Generally, growers wear gloves and protective clothing when handling Onosma plants because their protective hairs may cause irritation.

As natives of parts of Turkey and the Mediterranean regions, Onosma plants prefer temperate climates. Where the temperature may drop below 45°F (about 7°C), growers raise them in greenhouses or containers. They are difficult to transplant and generally like to stay where their seeds sprout.

The flowers grow on scorpioid cymes, meaning that the flower stem curves like a scorpion's tail and the bell-like flowers dangle from it. The flower stem generally uncoils as the flowers bloom, similar to a scorpion uncurling his tail. Typically, the flowers consist of a long five-lobed calyx surrounding a tubular corolla rimmed at the mouth with five lobes resembling petals. In some species, the flower mass appears to be a ball of flowers when in full bloom.

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The oblanceolate-shaped to narrowly oblong-shaped leaves of the Onosma plants often are radical, arising from the root or stem base. Generally, they are cauline, growing on the upper part of the stem. They are hairy, often with fine hairs that may irritate a person's skin if he or she brushes against the plant. The leaves typically are dark green with a darker green vein running up the center from base to tip. When not in bloom, the plant is a mound of erect leaf fingers.

Some of the cultivars that gardeners value are the O. alborosea, O. frutenscens,, and O. echioides, commonly called golden drop. The O. alborosea flowers mature from white to deep purple, while the O. frutenscens flowers change from bright yellow to an orangish or reddish brown. The flowers of the former species measure approximately 1.25 (3 cm) long, while the latter flowers are almost half that size. Another popular plant is O. stridii, which has an attractive maroon-tinted green calyx and stem that contrast beautifully against the long snow-white flower funnels.

Gardeners often raise Onosma plants in rock gardens. The plants typically thrive in scree beds and in rocky crevices, which are characteristic of their native habitats. A scree bed is a deep layer of stone chips or small rocks containing very little soil, similar to the conditions at the bottom of a rocky cliff. Some gardeners use Onosma plants in small garden settings, especially in dry, sandy soil.

Many of the members of the borage family have medicinal uses. O. argentatumn produces a substance that may be effective as an antimicrobial treatment for staph infections, bacteria, and Escherichia coli. Some herbalists use it for treating burns and wounds, and healers in rural Turkey use O. sericeum and O. microcarpum to treat wounds. O. echiodes may be able to slow tumor growth, and scientists are studying its healing properties. In the non-medical arena, O. hispidum produces a red dye that manufacturers use for food coloring, dyeing medicine, and even dyeing wool.

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