This evergreen perennial prefers moist or wet soil and can grow in boggy conditions at stream and lake shores. It spreads by seed and the clump enlarges by rooting stems. It is not usually a garden pest and is loved by many. It is a native of Europe and Asia, but was introduced to North America and is now naturalised. The species name refers to the shape of the stem as it emerges in a coil similar to a scorpion tail.
The leaves have a covering of fine hairs, arranged in pairs up the stem. the plant can grow up to 45cm with a spread of about 60cm.
The flowers are 8 to 13mm in diameter, pale blue with a yellow centre and white honeyguides, appearing between May and October. They bear both male and female parts and are pollinated by flies, bees, moths and butterflies. The calyx has flattened or sometimes no hairs.
The plants are easily uprooted and should be removed before flowering.
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