This herbaceous perennial wildflower is 3-6' tall and unbranched or
sparingly so. The central stem is green, stout, and terete, bluntly
angular, or ribbed; it is sparsely short-pubescent along the upper half
length, becoming glabrous below. Alternate compound leaves occur along
the entire length of the stem that are evenly pinnate with 6-12 pairs
of leaflets. Individual leaflets are 1¼-2½" long and ½-1" across; they
are oblong-elliptic in shape and smooth along their margins. The upper
surface is medium green or bluish green and hairless, while the lower
surface is pale
green or bluish green, often glaucous, and hairless.
At the base of each leaflet,
there is a short petiolule (basal stalklet) 1/8" (3 mm.) long or less.
petioles of compound leaves are 2-6" long, light green, grooved along
their upper surfaces, and either sparsely short-pubescent or hairless.
At the base of each petiole, there is a pair of small stipules that are
linear-lanceolate in shape and tardily deciduous. Along the upper side
of each petiole near its base, there is a small gland that functions as
an extra-floral nectary; this gland is often dome-shaped and dark
gray-purple, with or without a short stalk at its base. The crushed
foliage has an unpleasant scent.
Both terminal and axillary
inflorescences are produced. The terminal inflorescence is ½-1' long,
consisting of either a raceme or panicle of flowers. The axillary
inflorescences are up to ½' long, consisting of racemes of flowers.
Individual flowers are about ¾" across, consisting of 5 spreading
yellow petals, 5 spreading greenish yellow sepals, 10 stamens with dark
brown anthers, and a pistil with a style that curls upward at its tip.
The sepals are
smaller than the petals; the former are joined together at the base and
obovate in shape. The stamens are organized into three groups: the
lower 3 stamens have long filaments and long anthers, the middle 4
stamens have short filaments and long anthers, while the upper 3
stamens have short filaments and short anthers. Of these, the lower and
middle stamens are fertile, while the upper stamens are sterile. The
slender green styles are covered with short appressed hairs. The
flowers are without nectaries. The stalks of each inflorescence are
green, often angular, and usually short-pubescent. The blooming period
occurs from mid- to late summer for about 3-4 weeks.
afterwards, the flowers are replaced by drooping seedpods. These
seedpods are narrowly oblong in shape and flattened with single-seeded
segments. They are initially green and their sides are covered with
appressed short hairs, but they become dark brown and more hairless at
maturity, dividing into two parts along its length to release the
seeds. Individual seeds are a
little less than ¼" long, dark-colored, oblongoid-ovoid in
shape, flattened, and more
pointed on one end than the other. The
shallow root system is fibrous and long-rhizomatous. Small colonies of
clonal plants often develop from the rhizomes.
The preference is full or partial sun, moist well-drained conditions,
and soil containing loam, sand, rocky material, or other soil
types. The root system
does not add nitrogen to the soil, unlike many species in the closely
related Bean family (Fabaceae). This tall flowering plant is easy to
cultivate in gardens.
Maryland Senna is widely distributed throughout Illinois, but it is
relatively uncommon (see Distribution
). Populations of this species appear to be
declining. Habitats include moist prairies, openings in wooded areas,
thickets, savannas, riverbanks, and limestone glades. Occasionally this
wildflower is cultivated in gardens. In wooded natural areas, some
is required to reduce competition from trees and shrubs.
The flowers are cross-pollinated by
collect pollen from the flowers. The extra-floral nectaries attract
ants and occasionally flies, which feed on the nectar. The foliage of
Maryland Senna and the closely related Wild Senna (Senna hebecarpa
consumed by caterpillars of the butterflies Eurema nicippe
Orange), Phoebis philea
(Orange-barred Sulfur), and Phoebis
(Cloudless Sulfur). The foliage is also eaten by the caterpillars
of Epargyreus clarus
(Silver-Spotted Skipper) and Ascalapha
(Black Witch), while the flowers are eaten by
caterpillars of the polyphagous moth, Pleuroprucha insulsaria
(Common Tan Wave). A negro bug, Cydnoides
, has been found in association with Maryland
Senna, other Senna
(Sennas), and Cassia
(Partridge Peas); they are possible host plants of
Because the foliage is somewhat toxic and cathartic, it is usually
avoided by White-Tailed Deer and other mammalian herbivores.
A woodland opening at Busey Woods in Urbana,
A scientific synonym of this species is Cassia marilandica
common name of this wildflower is Southern Wild Senna, because
its range doesn't extend as far north as a closely related
species, Senna hebecarpa
(Wild Senna). These two species are very
similar in appearance and they are occasionally confused with each
other. The flowers of Maryland Senna have styles with short appressed
hairs, while the flowers of Wild Senna have styles with long spreading
hairs. Maryland Senna also tends to produce fewer flowers
than Wild Senna, although variations in environmental conditions can
produce exceptions to this rule.