Scarlet pimpernel is a low-growing annual plant.
Commonly known as blue-scarlet pimpernel, red pimpernel, red chickweed, poorman’s barometer, poor man’s weather-glass, shepherd’s weather glass or shepherd’s clock.
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”.
A common annual weed in Pakistan.
Stem decumbent to erect, not rooting at the nodes, square in outline.
Leaves sessile, opposite-decussate, pale green, 10-16 x 7-12 mm, ovate-oblong, obtuse or subacute, upper ones smaller, nerves faint, gland dotted (dots reddish), margin minutely papillose.
Flowers solitary axillary, red or blue (or shades of them); pedicel 1.4-2.5 (-3.5) cm long, slender, glandulose (hairs with reddish heads), nodding in bud condition, usually exceeding the subtending leaf.
Calyx shortly campanulate; lobes 3.5-4 mm long, ovate-lanceolate, subacuminate, midrid pro¬minent, margin membranous and minutely ciliolate.
Corolla rotate; lobes 4-5 mm long, obovate, apex erose-denticulate, glandular-stipitate; the glands 3-celled, with the terminal cell globose.
Stamens ± equalling the carpel; filaments 2-2.5 mm long, reddish-pink, basally dilated and connate; glandular, the glands 7-11-celled, pinkish, towards base colourless; anthers 1 mm long, basifixed, yellow, ± apiculate.
Ovary globose, less than 1 mm broad; style 2-2.2 mm long, pinkish, persistent.
Pyxidium globose, 4-5 mm broad. Seeds trigonal, c. 1 mm broad, dark brown, vesiculose.
The native range of the species is Europe and Western Asia and North Africa. A. arvensis is now naturalised almost worldwide, with a range that encompasses the Americas, Central and East Asia, the Indian Subcontinent, Malesia, the Pacific Islands, Australasia and Southern Africa.
This common European plant is generally considered a weed and is an indicator of light soils. It has been reported as being toxic to poultry and rabbits, and the seed to birds.
Anagallis arvensis is insecticidal, or at least is repellent to some insects, possibly by virtue of its pungent essential oil which has a characteristic smell.