Round-leaved Mint
Scientific name: Mentha suaveolens Ehrh.
Diagnostic features
Plant pubescent, with sickly scent.
Stems erect, to 1m.
Leaves oblong-ovate to suborbicular, strongly rugose, with teeth bent under and hence appearing as blunt crenations, sessile or ± so.
Upper whorls in axils of bracts, congested to form very narrow often much-branched panicle of spike-like heads.
Calyx bell-shaped, 1-2mm.
Corolla usually whitish.
Chromosome number: 2n=24.
Habitat
Native; ditches and other damp places, waysides.
Distribution
Locally frequent in West & South Wales, Southwest England and Channel Islands, naturalized sparsely elsewhere in British Isles.
This species is keyed out on Page 3116 in the Text Key.
Notes
This species belongs to the Mentha spicata group, involving Mentha spicata (tetraploid), Mentha suaveolens (diploid) and their hybrids with each other and with the non-British Mentha longifolia (diploid), are particularly difficult, especially owing to the great variation of Mentha spicata, which is itself derived from Mentha longifolia x Mentha suaveolens. The 2 triploid hybrids are sterile, but the diploid hybrid and the species are fertile in bisexual plants or in female plants open to a pollen source. Pubescent plants that are not Mentha suaveolens are often impossible to name for certain. Characters of Mentha suaveolens often seen in its hybrids are the broad, obtuse, very rugose leaves with teeth partly folded under the margin and with patchy or clumped indumentum on lowerside; of Mentha longifolia are the lanceolate-oblong, acute, flat leaves with sharp patent teeth and with felted grey indumentum; and of Mentha spicata are the lanceolate to ovate, acute, not to slightly rugose leaves with usually forward-directed teeth and relatively coarse pubescence. Mentha spicata is the most variable; very broad-leaved plants, and strongly rugose-leaved plants occur, but this is the only species of the 3 that can be glabrous to sparsely pubescent and the only species that can smell of spearmint. Hybrids (especially Mentha villosa(x)) can be very variable, showing many combinations of characters not always connected by intermediates, but they do not exactly duplicate the combinations shown by any of the species.
Hybrids
- Mentha x carinthiaca Host (= Mentha arvensis x Mentha suaveolens) (Synonym: Mentha x muelleriana F.W. Schultz) occurred in South Devon and Dorset but is now extinct; it is similar to Mentha arvensis but has usually larger, broader leaves with deeper, sharper serrations and is sterile. Chromosome number: 2n=60.
- Mentha x suavis Guss. (= Mentha aquatica x Mentha suaveolens) (Synonym: Mentha x maximilianea F.W. Schultz) occurs near the parents in West Cornwall, North Devon and Jersey; it is similar to Mentha aquatica but has more rugose leaves with more cordate base, and much narrower (c.9-15mm) often longer terminal heads. Chromosome number: 2n=72, 84.
- See Mentha villosa(x) Huds. (= Mentha spicata x Mentha suaveolens) |
