A cottage garden plant of old, this creeping variety has prostrate stems which carpet the ground and root from the leaf nodes as they spread. Attractive whorls of lilac-blue flowers appear in mid to late summer, held above the foliage on stout stems.
It can be used to carpet a shady corner or make a “lawn” smelling deliciously of peppermint, also useful to make a scented seat. It is found wild and naturalised throughout the civilized world in strong, moist soil on the borders of ponds and streams, and near pools on heaths and commons.

A highly aromatic herb, with a strong peppermint scent to its dark green leaves, even more so than other mints, and is so named for its reputed power to drive away fleas. Pulex being the Latin for flea, hence the Italian pulce and the French puce.
It was formerly much used medicinally and is still in culinary usage abroad but in this country the taste and odour are too pronounced for our taste buds. In France and Germany the essential oil is still used commercially.
One of its popular names is 'Pudding Grass,' from being used in stuffings for hog's puddings ('grass' simply meaning 'herb').

In the UK, pennyroyal is now found in abundance only in the New Forest and on the western shores of Lough Beg in Northern Ireland. It has suffered one of the most severe and widespread declines of any species in the British flora over the last 50 years. Before 1970 it was known from 229 ten km squares, but has been recorded in only 15 of these since 1980. It is widespread in Europe where it is not threatened as a whole, but it is declining in many areas (e.g. Germany).
In Britain this species is now classified as Vulnerable, and is specially protected under Schedule 8 of the Wildlife and Countryside Act 1981

Sowing: Late winter/late spring and late summer/autumn.
It is easily grown from seed and succeeds best in a moist situation.
Surface sow at 15mm (1/16in) deep in pots or trays containing good seed compost. Do not cover the seed as they need light for germination.
Make sure the compost is moist but not wet and seal inside a polythene bag until germination which usually takes 5 to 21 days at 20°C (68°F).
Transplant the indoor seedlings when large enough to handle into pots and grow on. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts. Their ideal position would be in full sun, with a fertile soil that is not too wet. Space 30cm (12in). Water regularly until mature.

Cultivation:
Prune in spring or after flowering to encourage bushiness. It self-seeds easily when happy, so deadhead it if you don't want a lot more rue. It is perennial, but mulch in winter in very cold areas. Once it gets going, you can propagate it by cutting off the tips of branches and rooting them.

Harvesting:
Pennyroyal is mostly sold and used in the dry state for making tea, the stems being cut when the plant is just about to flower and dried in the usual manner.

Medicinal Uses:
The most popular current use of the tea is to settle the stomach, but should be taken in small amounts and never be consumed by pregnant women. Please consult a qualified herbal practitioner. (Note – Oil of Pennyroyal should never, ever be taken internally!)

As a Deterrent:
Traditionally the herb is planted between paving stones to deter ants. It is an effective deterrent of fleas and is also thought to repel mice. Dried pennyroyal has also been recommended as a natural flea control.
Pennyroyal is highly toxic to cats, although they generally avoid it, it should not be planted where they might ingest it and should never rubbed onto their skin.