Lysimachia arvensis platyphylla (Lysimachia arvensis platyphylla)

Description

When found as a summer annual, the Scarlet Pimpernel has a low-growing creeping habit, but as a winter annual, it forms a half-rosette with an upright stem. It has weak sprawling stems with square cross-section growing to about 5-30 centimetres (2-12 in) long. They bear bright green, soft, ovate sessile leaves in opposite pairs. The orange, red or blue, radially symmetric flowers, about 10-15 millimetres (0.4-0.6 in) in diameter, are produced singly in the leaf axils from spring to autumn. The petal margins are somewhat crenate and have small glandular hairs. The stamens have lollipop hairs and therefore attract a variety of pollinators, especially flies, but the flowers are also capable of autopollination. The dehiscent capsule fruits ripen from August to October in the northern hemisphere. The weight of the fruiting body bends the stem, and the seeds are transported by the wind or rain. Blue-flowered plants (A. arvensis Forma azurea) are common in some areas, such as the Mediterranean region, and should not be confused with the related Blue pimpernel, Anagallis foemina, sometimes ssp. foemina. In 2007, a molecular phylogenetic study showed that Anagallis foemina is more closely related to Anagallis monelli than to Anagallis arvensis, and should be treated as a separate species.The taxonomy has however not yet been resolved and various authorities propose either the subspecies Anagallis arvensis subsp. foemina (Mill.) Schinz & Thell, or the species Lysimachia foemina (Mill.) U.Manns & Anderb.The plant has a diploid chromosome count of 2n=40.Scarlet pimpernel flowers open only when the sun shines, and even close in overcast conditions.This habit leads to names such as "shepherd's weather glass". It has recently started to occur along the verges of salted roads, creating a broad red band along the roadside.The Scarlet Pimpernel has a wide variety of flower colours. The petals of the type arvensis are bright red to minium-coloured; carnea is deep peach, lilacina is lilac; pallida is white; and azurea is blue. The blue form can be difficult to distinguish from A. foemina, but the petal margins are diagnostic: whereas foemina has clearly irregular petal margins with only 5 to 15 glandular hairs, A. arvensis f. azurea has 50 to 70 hairs on only slightly irregular margins.