Thymes & Mints
What are they?
These species are all members of the Lamiaceae, the Labiate family. This group of plants are all highly aromatic in all their parts. Their flowers are rather different to those of most other labiates in having four, more or less equal petal lobes, without the 'hooded', enlarged upper lip of other labiates. The majority of these plants are well-known for their use as culinary herbs.
Where are they found?
These are mostly plants of open heaths and areas of short grass. Some species are non-native and occur as garden escapes, so may turn up on roadsides and waste places in urban areas.
Identification
Separating some of these species can be difficult and sometimes requires careful attention to details. With the thymes, it pays to check the arrangement of the hairs on the square-sided stems, while the mints can be problematic due to the high incidence of hybrids in this group. Note that plants in this family have the five sepals fused together into a tube, known as a calyx. The tip of each sepal is usually pointed and therefore the calyx has five teeth and the size and shape of these teeth can be useful for identification, especially in some of the mints.
Water Mint Mentha aquatica
Widespread in wetland habitats. Flowers July to October. A strongly aromatic species with a rich, minty smell. Flowers in tight clusters in the upper leaf axils towards the top of the plant, with a rounded cluster topping the main stem. The calyx teeth are long, narrow and sharply pointed.
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Corn Mint Mentha arvensis
Widespread in damp soil on the edges of grassy tracks and fields. Flowers June to October. A strongly aromatic species with a rich, minty smell. Flowers in tight clusters in the leaf axils, with the stems topped with small leaves, not flowers. The calyx lobes are about as long as they are wide, forming an equilateral triangle.
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Whorled Mint Mentha x verticillata
Widespread but uncommon in damp soil on the edges of grassy tracks and rough ground. The hybrid between Water Mint and Corn Mint and sometimes found in the absence of both parents. Flowers June to October. A very variable plant in the size, shape and hairiness of the leaves. Said to have a 'sickly scent' but this is not apparent to some people. Flowers often have stamens that don't project beyond the mouth of the flower, but this is not always the case (as in the photos here). Calyx 2.5-4mm in length, including teeth of more than 1mm, with the calyx tube more than twice as long as wide. The plant generally has the look of an over-sized Corn Mint, with stems 30-90cm in height, but with the calyx lobes being twice as long as wide.
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Ginger Mint Mentha x gracilis
(Bushy Mint) The hybrid between Spear Mint and Corn Mint which is often grown as a garden herb and occasionally escapes, though there were far more records in the past and it is not much recorded these days. Flowers August to October. A very variable plant in the size, shape and hairiness of the leaves, with the form grown in gardens as 'Ginger Mint' often having variegated leaves. Flowers all in whorls in the leaf axils. Calyx 2-3.5mm in length, including teeth of less than 1mm, with the calyx tube less than twice as long as wide.
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Apple Mint Mentha x villosa
A hybrid species, grown commercially and often found spreading from dumped garden waste. Flowers August to September. A spreading plant with rounded leaves and a sweet, minty or spearmint aroma. Flowers pale pink in long, sometimes branched, terminal spikes. The teeth on the leaf edges are not strongly down-turned, giving the leaves a sharply-serrated edge.
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Round-leaved Mint Mentha suaveolens
A rare native in SW England but only a casual escape from cultivation in East Anglia. Flowers August to September. A spreading plant with rounded leaves and a rather sickly-sweet aroma. Flowers white in long, usually branched, terminal spikes. The teeth on the leaf edges are strongly down-turned, giving the leaves the appearance of having rounded lobes along the margins when viewed from above.
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Spear Mint Mentha spicata
Very popular and widely grown as a garden herb and frequent escaping onto waste ground and roadsides. Flowers August to September. A rather agressive, spreading perennial plant, smelling strongly of spearmint. Leaves hairless, lance-shaped, with sharply-toothed margins. Flowers pink or white, in elongate spikes.
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Pennyroyal Mentha pulegium
Once native, this species was long lost from the region due to draining of its favoured habitat of seasonally-flooded grasslands; however it is currently plentiful on a site in South Norfolk, though probably of cultivated origin. Elsewhere, it is uncommon as a garden plant but occasionally found as a garden escape. Flowers August to September. native plants were low and creeping but plants of cultivated origin are more upright. Leaves small, ovate.
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Corsican Mint Mentha requienii
Introduced from southern Europe as a garden ornamental and found twice as an escape from cultivation in Suffolk. Flowers June to August. A minuscule plant with leaves no more than 5mm long and tiny flowers carried in clusters of six or less. Looks rather more like a low, creeping thyme than a mint.
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Common Marjoram Origanum vulgare
A native of thin, chalky soils, thinly scattered in suitable habitat but can be quite common in suitable habitat on old banks and commons. Flowers July to September. An upright, clump-forming species with a rich, herby smell. Pale pink flowers appear in flattened heads among reddish bracts.
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Large Thyme Thymus pulegioides
A species of short-grazed grassland on usually chalky soils; common in Breckland but rare and scattered elsewhere. Flowers July to August. A wiry subshrub with a strong thyme smell. The flowerheads tend to be a little larger than those of other thymes, but it is best told by the stems, which have long hairs only on the corners and short down on just two of the four sides.
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Wild Thyme Thymus praecox subsp. britannicus
(Thymus drucei, Thymus polytricchus) A species of short-grazed grassland on chalky soils. Most frequent in Breckland but rare and scattered elsewhere. Flowers June to August. A wiry subshrub with a strong thyme smell. Best told from other thymes by the stems, which have dense hairs on two sides of the stem and no hairs on the other two sides.
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Breckland Thyme Thymus serpyllum
A rare native, in the UK confined to Breckland in Norfolk and Suffolk. Flowers July to August. A creeping subshrub with a lemon-thyme smell. Very showy when in flower, but it is best told by the stems, which are less four-angled than on Wild and Large Thyme and are equally hairy on all sides.
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Common Thyme Thymus vulgaris
Introduced from the Mediterranean region as a culinary herb and twice recorded in Norfolk as a garden escape. Flowers July to August. A wiry-stemmed perennial, usually more upright than our native thymes. The whole plant has a grey-green look and the stems are rounded and roughly downy. The leaves have distinctly down-turned margins.
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