Mint family (Lamiaceae)
This perennial plant is about ½–¾' tall and occasionally to abundantly
branched. The foliage of this plant smells like mint when it is
crushed. The stems are light green to reddish purple, 4-angled, and
glabrous or nearly so; sometimes the sides of the stems have
longitudinal central grooves. Pairs of spreading opposite leaves
occur along these stems. Individual leaves are ½–1" long and about 3
mm. (1/8") across; they are linear to linear-oblong in shape, entire
(smooth) along their margins, and sessile. Smaller pairs of
secondary leaves often develop from the axils of the preceding leaves,
and sometimes even smaller tertiary leaves develop from the axils of
the secondary leaves, causing the leaves along the stems to appear
whorled. Both the lower and upper surfaces of these leaves are
yellowish green to medium green and glabrous; both surfaces are also
pitted with transparent glands (use a 10x hand lens to see). The tips
of the leaves are bluntly acute to acute. Individual leaves have
prominent central veins.
Solitary flowers develop from the axils of the
leaves. Because such flowers can develop from primary, secondary, and
even tertiary leaves, they often appear to occur in clusters (up
to 6 flowers per node). Each flower is about 12 mm. (½") long,
consisting of a pale lavender (rarely white) trumpet-shaped corolla
with 2 lips, a light green to reddish purple calyx that is tubular in
shape with 5 teeth, 4 stamens with pale lavender anthers and white
filaments, and a pistil with a single divided style. The corolla is
slightly compressed (flattened), becoming wider toward its lips; the
upper lip consists of a pair of adjacent
upper lobes that are erect-recurved, while the lower lip consists of 3
lower lobes that are
slightly descending and spreading. All of these lobes have rounded
margins. The outer upper surface of the corolla is finely hairy.
Two stamens are slightly exserted near the upper lip, while the
remaining pair of stamens are inserted. The style is also inserted
within the corolla.
The tubular calyx is about one-third the length of
the corolla; it is slightly compressed (flattened) and there are 10
longitudinal ribs along its length. The teeth of the calyx are narrowly
triangular. The slender pedicels of the flowers are 6-10 mm.
(about 1/3") in length. The blooming period occurs from
early to late summer, lasting about 2-3 months. Afterwards, the flowers
are replaced by small nutlets (4 nutlets per flower). These nutlets are
to 1 mm. across, brown, and finely pitted. The root system is fibrous
and stoloniferous. Outside of the main growing season, this plant also
produces a low rosette of basal
leaves; the latter are substantially wider than the opposite leaves.
Cultivation: The preference is full or partial
sun, moist to mesic conditions, and
calcareous soil that is sandy or rocky. This plant could be cultivated
in sunny rock gardens. It doesn't tolerate much competition from taller
ground vegetation. Standing water is tolerated if it is temporary.
During hot dry spells, this plant should be watered.
& Habitat: Low Calamint occurs primarily
in NE Illinois, where it
is uncommon and native (see Distribution
Map). Rather oddly, this plant
is widespread in Missouri, but it hasn't been found in southern
Illinois. Habitats consist of mesic gravel prairies, sandy savannas,
limestone glades, limestone cliffs, rocky areas along springs, moist
sand flats along Lake Michigan, and fens. Low Calamint is found in high
quality natural areas.
Associations: The flowers are probably
cross-pollinated by bees. Both
nectar and pollen are available as floral rewards. The larvae of a fly,
Ophiomyia labiatarum, bore through the stems of
Calamint species (Spencer &
Steyskal, 1986). Because the foliage of this plant has a strong mint
fragrance, it is probably avoided by mammalian herbivores.
wildflower garden of the webmaster, and the edge of a sand flat near
Lake Michigan in NE Illinois.
Comments: Low Calamint (Clinopodium
arkansanum) has an
history, and it has several scientific synonyms, including Satureja
arkansana, Satureja glabella angustifolia,
Calamintha arkansana, and Clinopodium
glabrum. Another common name for this
plant is Limestone
Calamint. It is a bushy-looking little plant that becomes attractive
during its peak flowering period (typically mid-summer), when numerous
small flowers are in bloom at the same time. It also has a fairly long
period of bloom. Low Calamint can be distinguished from similar plants
by the strong mint fragrance of its crushed foliage, hairless or nearly
hairless foliage, short narrow leaves without significant teeth, finely
ribbed calyces, and solitary axillary flowers (although it can appear
to have clusters of flowers if secondary and tertiary leaves are
produced). Other species of plants in the Mint family that have foliage
with a mint fragrance include mint, spearmint, and peppermint (Mentha
spp.), and American Pennyroyal (Hedeoma pulegioides).
Compared to Low
Calamint, the various mints have wider leaves with conspicuous teeth
and their flowers occur in dense axillary or terminal clusters.
American Pennyroyal differs by having hairy stems, slightly wider
leaves with petioles, and smaller flowers (about 6 mm. or ¼" in length)
with shorter pedicels.