Scarlet pimpernel

THERE AREN’T MANY WEEDS that adorn your pasture. But scarlet pimpernel's scientific name – Anagallis arvensis – means 'adornment of the fields', a reference to its unusual ability to close its flowers when the sun disappears. That's also why its other common names are 'poor man's barometer' and 'shepherd's clock'.

If you're wondering what the link is to the famous book, The Scarlet Pimpernel, the flower is the emblem of the book's hero, Sir Percy Blakeney.

Scarlet pimpernel is a small and scrambling plant, widely distributed across the world and a member of the primrose family ( Primulaceae).

Its native to North Africa, Europe and Western Asia, but this weed is a world traveller, crossing the globe both by accident and deliberate distribution as an ornamental flower.

It likes New Zealand growing conditions. When it has favourable temperatures, scarlet pimpernel establishes almost anywhere: flower gardens, crops, ditches, hedges, pastures. Soil type isn't specific, although the plant is more competitive in open spaces or recently cultivated soil with a good measure of sunlight.

This weed has a number of distinguishing features:

prostrate stems that scramble along the ground, crawling up and over objects;

the stems are actually square and hairless which makes them easy to identify when compared with other common pasture and garden weeds such as chickweed (circular hairy stems with white flowers) or staggerweed (hairy stem with ridged leaves);

some leaves which branch directly off the stem (with no stalk), perpendicular in opposite pairs;

the leaves are oval-shaped with a hairy underside that is also dotted with small black glands.

This weed is most noticeable in flower, when it's at its highest, about 40cm. The orange flowers open predominantly in sunlight. They can attract a variety of pollinators thanks to the upright nature of the stamens, the pollen-producing organ of the flower.

However, one of the secrets of its worldwide success is its ability to autopollinate once the flower closes.

How to control it

You can easily pull scarlet pimpernel out of the ground.

There is also a wide range of chemical options available to eradicate it – check the label and find one that best suits your conditions.