Mentha L.
Family: Lamiaceae
Mentha image
Christopher Noll  

Key to Wisconsin Mentha

Author: John G. Zaborsky

    • 1a. Flowers in the axils of typical leaves, these gradually reduced in size distally 2

    • 1b. Flowers all or mostly in crowded terminal inflorescences without conspicuous bracteal leaves between the whorls 3

    • 2a. Bracteal leaves smaller distally but still petiolate and resembling the principal foliage leaves; calyx tube pubescent M. canadensis

    • 2b. Bracteal leaves greatly reduced distally to sometimes inconspicuous bracts not exceeding the flowers, usually sessile or sometimes with very short petioles; calyx tube glabrous, the lobes ciliate M. × gracilis

    • 3a. Leaves glabrous or nearly so 4

    • 3b.Leaves densely pubescent 5

    • 4a. Inflorescence head-like, the verticillasters densely packed (the lowermost usually separated by a long internode), nearly the same thickness throughout and rounded at its apex; leaves petiolate, ovate M. × piperita

    • 4b. Inflorescence spike-like, the verticillasters widely separated (at least proximally), tapered to an acute apex; leaves sessile or with short petioles not longer than 3 mm, lanceolate M. spicata

    • 5a. Fertile anthers 4; leaves oblong-lanceolate to ovate, with nearly parallel sides M. × rotundifolia

    • 29b. Fertile anthers 0; leaves ovate to suborbicular M. × villosa

This is a taxonomically difficult genus due to hybridization, morphological plasticity, and a long history of cultivation. Matters are only made worse by the hundreds of (often misused) superfluous names that have been given to the many variants. Since most of our introduced taxa are hybrids, they are included in the key below. Other hybrids have been attributed to the state but don’t appear to be widespread (or may not be correctly identified) and are not accounted for here. Considering the large amount of hybridization and backcrossing in the genus, it seems easiest to only treat the most commonly encountered taxa.
Species within Green Lake County 2016