1. Tanacetum balsamita L. (costmary, mint geranium)
Chrysanthemum
balsamita L.
C. balsamita var. tanacetoides Boiss.
Balsamita
major Desf.
B. major var. tanacetoides (Boiss.)
Moldenke
Pl. 228 h, i;
Map 955
Plants with
rhizomes. Stems 30–120 cm long, glabrous toward the base, sparsely to
moderately hairy toward the tip. Leaves 1–27 cm long, the basal and
lower stem leaves usually much larger than the others, long-petiolate, grading
relatively abruptly into the short-petiolate to sessile median and upper stem
leaves. Leaf blades simple and unlobed or the lowermost rarely with a few deep,
irregular basal lobes, oblanceolate to elliptic, mostly rounded at the tip,
angled to long-tapered at the base, the margins bluntly and evenly toothed,
both surfaces moderately to densely glandular and densely pubescent with
appressed, grayish, silky hairs when young, sometimes the lowermost becoming
glabrous or nearly so at maturity. Heads usually discoid. Involucre 3–7
mm long, cup-shaped, the bracts in 3–5 series, the main body narrowly
lanceolate to lanceolate-triangular, tapered to a conspicuous, thin, papery
tip, the margins also thin and nearly transparent, the outer surface glandular
and hairy. Ray florets absent or the marginal florets sometimes pistillate,
occasionally somewhat raylike but inconspicuous and not markedly enlarged,
usually white. Disc florets with the corollas 1.5–2.7 mm long. Pappus a
short collar or crown. Fruits 1.3–1.6 mm long, more or less circular in
cross-section, mostly obscurely 10-ribbed. 2n=18, 54.
August–October.
Introduced,
known thus far from a single historical collection from Franklin County (native of Europe, Asia, introduced widely in North America). Fencerows and open,
disturbed areas.
Tanacetum
balsamita escapes and
becomes naturalized sporadically, most commonly in New England and the Great Lakes region. Some botanists have segregated the species into its own genus, Balsamita
Mill., based primarily on its unlobed leaves, but most botanists do not believe
that the differences merit recognition of a separate monotypic genus (Soreng
and Cope, 1991; Bremer, 1994). The rayed forms sometimes have been called var. tanacetoides
Boiss.