Mentha x, L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1972, Flora Europaea. Volume 3. Diapensiacea to Myoporaceae, Cambridge: Cambridge University Press : 185

10. M. x piperita L. , Sp. Pl. 576 (1753)

( M. nigricans Miller ) (AT. aquatica x spicata ).

Perennial 30-90 cm, with a pungent scent, usually subglabrous but occasionally hairy to greytomentose, often purple-tinged. Leaves 40-80(-90) x 15-40 mm, ovate-lanceolate or lanceolate, rarely ovate, cuneate to subcordate and long-petiolate, usually serrate. Inflorescence usually of numerous congested verticillasters with inconspicuous bracts forming a terminal, oblong spike (3O-)5O-8Ox 12-18 mm, often interrupted below, rarely a narrow elongate spike or subglobose head. Calyx 3 4 mm, tubular, the tube usually glabrous; teeth ciliate. Pedicels usually glabrous. Corolla lilac-pink. Sterile. 2« = 66, 72. Widespread as a garden escape and also spontaneous. [Au Az Be BI Br Bu Cz Da Ga Ge G r Hb He Ho Hs Hu It Ju Lu Po Rm Rs (C, W, E) Si.] The subglabrous plants were formerly widely cultivated and have escaped to become well naturalized in many areas. They are usually easy to recognize. Hairy plants may have arisen spontaneously where both parents occur. They are much more variable in shape of leaf and inflorescence, and in scent, and are readily confused with M. x dumetorum (see below). Without field information and further cytological study the limits of the two are uncertain.

M. x piperita nm. cifrata (Ehrh.) Boivin, Naturaliste Canad. 93: 1061 (1966) (AT. odorata Sole, AT. adspersa Moench), a sterile cultivar with In = 84, 120, is widely cultivated and occasionally naturalized. It has a strong scent resembling Eau de Cologne, glabrous or subglabrous ovate, subcordate leaves, and an inflorescence like that of 9, but smaller.

M. x maximilianea F. W. Schultz , Pollichia 12: 34 (1854) (AT. rodriguezii Malinv., AT. suavis Guss., AT. schultzii Bout. ) (AT. aquatica x suaveolens ), with 2« = 60, 72-78, 120, occurs occasionally in the vicinity of both parents, and is intermediate between them and usually sterile, although fertile back-crosses are reported. It has been confused with AT. x dumetorum and 10. M. xtutinii P. Silva in Palhinha, Cat. Pl. Vase. Açores 103 (1966), from the Açores, which reputedly is 10 x 11, appears to be a narrow-leaved variant of 9 x 11.

M. x dumetorum Schultes , Obs. Bot. 108 (1809) (AT. pubescens auct.,? an Willd., AT. nepetoides Lej., AT. ayassei Malinv., AT. hirta Willd. ) (AT. aquatica x longifolia ), occurs in many places in the vicinity of its parents, but, owing to confusion with hairy variants of 10, its distribution and frequency are uncertain. M. x pyramidalis Ten. , FI. Nap. 1, Prodr.: 34 (1811) (AT. reverchonii Briq. ) (AT. aquatica x microphylla ), with 2zi=c. 72, occurs in S. Italy and Kriti. (11-14). M. spicata group. Leaves sessile or the lower very shortly petiolate. Flowers in slender spikes 5-15 mm in diameter. Nutlets red-brown to black, reticulate (except in glabrous variants of 14).

In the key no attempt has been made to include the vast array of cultivated and wild hybrid variants; those involving AT. spicata are usually recognizable by their sterility. Among the most valuable characters are the indumentum on the lower surface of the leaves and the length of the fertile anthers and nutlets. Glabrous plants or those with the sweet scent of 14 can unhesitatingly be referred to this species or one of its hybrids, although the absence of these characters is no positive indication to the contrary. 1 Stems and leaves glabrous or sparsely hairy 14. spicata 1 Stem and leaves hairy

2 Leaves not more than 45 mm, with numerous branched hairs beneath

3 Leaves 20-40 mm wide, ovate-oblong to suborbicular, obtuse, sometimes minutely apiculate, rarely subacute; verticillasters crowded, except at base 11. suaveolens 3 Leaves 5-20 mm wide, ovate to ovate-lanceolate, usually acute; verticillasters distant 13. microphylla 2 Leaves (3O-)5O-9O(-11O) mm, branched hairs absent, or if present usually few beneath

4 Hairs all simple; leaves widest near the middle; fertile anthers 0-28-0-38 mm 12. longifolia 4 Some branched hairs usually present on the leaves beneath; leaves widest near the base; fertile anthers 0-38-0-52 mm

14. spicata