Scarlet Pimpernel is usually an annual spread by seed, preferring lighter, well-drained soils and as well as popping up occasionally in the garden, it is found among arable crops and on waste ground. It is not usually a problem and can be quite attractive on an informal path.
The Genera name comes from the Greek 'anagelao' for 'laugh' as it has some mention for use to lift low spirits. Other herbal uses include liver complaints an as a cure for hydrophobia (rabes). It was also said to ward off malevolent beings.

The leaves are stalkless with veins running their length and are arranged in opposing positions along the square stems. There are black gland-dots on the undersides. When growing in poor ground the plant is compact, reaching about 5cm in height, but in better conditions a more sprawling habit develops (main picture).

The distinctive flowers tend to open around 8 a.m. and close in the afternoon in warm sunny weather, but will also close up in dull conditions. This is the origin of many of the common names listed above. They are borne on a stalk arising in the leaf axils, appearing form June to August/September and are usually red-orange, but can be pink, lilac, blue-purple or white.

The plant is easily uprooted, but as there will probably be plenty of seed present so it will return.

A contact or a systemic weedkiller would both work. To keep a path clear use a residual agent which will prevent the seed from germinating.

See also Yellow Pimpernel, Chickweed and Bog Stitchwort which have similar foliage.

Follow these links for further details on Weeds, Weed Removal and Weed Prevention.