Pycnanthemum torreyi

Torrey’s Mountain Mint (Pycnanthemum torreyi)

Seven species of mountain mint (Pycnanthemum spp.) are found in New York. Of these, four are state listed as either threatened or endangered. These mountain mints include: blunt (P. muticum), whorled (P. verticillatum var. verticillatum), basil (P. clinopodioides), and Torrey’s (P. torreyi). Outside of New York, only the last two are widely regarded as rare.

Range & Protective Status

Torrey’s mountain mint currently ranges along the Appalachians from northern Georgia to New Hampshire. A southern arc extends from this same chain to the western reaches of Kentucky, Tennessee, and southern Illinois. There are only around 35 extant occurrences of this species. With such low numbers, it receives a G2 rating of “imperiled” on the global conservation scale. It is state endangered. While always rare, habitat loss caused by both development and succession, along with deer browse, has considerably reduced its range over the years. In New York, it is confined to the southeastern portion of the state where it continues to hold on in a few strongholds, such as in the southern Hudson Highlands.

Habitat

This species favors upland environments and can most frequently be found inhabiting dry, open woods or along forest margins. It performs best in sun-dappled conditions and can attain a height of over a meter. Plants situated in full sun are often stunted and the lack the lushness and vigor of those in shadier locales. At first glance, these stunted plants that can easily be mistaken for Virginia mountain mint (P. virginianum).

Juniper Hairstreak.

Identifying Characteristics

Since many species in the genus Pycnanthemum look similar and possess relatively minor distinguishing characteristics, not to mention their often-great morphological variation and propensity to easily hybridize, it can be a challenge to positively identify this species. Recent work cataloging herbarium specimens has revealed that numerous specimens identified as Torrey’s mountain mint have been mislabeled. Most of these erroneous classifications have proven to be P. torreyi’s closest congener, whorled mountain mint (P. verticillatum).

The prime identifying feature of Torrey’s mountain mint is its narrow lanceolate calyx teeth which range between 1.0-2.0 mm in length. Some sources indicate these are typically 1.0-1.5 mm; others, 1.5-2.0 mm. The calyx is actinomorphic or radially symmetric (not bilabiate). Whorled mountain mint has shorter, broader calyx teeth deltoid in shape that measure 0.5-1.0 mm. The florets of Torrey’s mountain mint usually have strongly exserted pollen-rich stamens, in contrast to the shorter and often abortive stamens of whorled mountain mint. Plants are in bloom from late June through September.

Lanceolate calyx teeth 1.0 – 2.0 mm in length. Actinomorphic or regular (radially symmetric) calyx. Pollen-rich, strongly exserted stamens.

Another diagnostic feature is that the stem is covered with fine, uniformly distributed hairs on both the faces and angles. Other species have glabrous or densely hoary stems, or those with hairs more prominent on the stem angles. What’s more, the top of the leaves of P. torreyi are glabrous (vs. the canescence of P. verticillatum). The bottoms of the leaves are sparsely pubescent, usually following along the midvein. The leaf margins may be entire or possess a few low teeth. Narrow, lanceolate leaves are borne on short petioles. Leaf width does not surpass 1.5 cm. Whorled mountain mint generally has slightly wider leaves than P. torreyi.

Fine hairs uniformly distributed. Glabrous upper leaf surface. Short petiole. A few low teeth on leaf margins. Leaf width of less than 1.5 cm. A few fine hairs on the midvein. Each floret bears tiny purple polka dots. Mountain mints are pollinator magnets.