This perennial wildflower is 4-12" tall; it is branched at the base
and often branched above. The ascending to erect stems are light to
hairy, and terete. Alternate trifoliate leaves occur at intervals along
the stems. The leaflets are ½-1½" long and 4-8 mm. across; they are
elliptic in shape, while their margins are entire (smooth) and ciliate.
The upper leaflet surface is medium green and glabrous to sparsely
short-pubescent, while the lower leaflet surface is light green and
sparsely short-pubescent. The petioles of the trifoliate leaves are up
to ¼" long, light green, and hairy. The base of each petiole and a
portion of the adjacent stem are surrounded by a pair of of green to
brown stipules; each stipule tapers to a ciliate beak. The terminal
leaflets have petiolules (basal stalklets) up to ¼" long, while the
lateral leaflets are sessile (or nearly so). Leaf venation is pinnate;
the veins along the upper leaflet surfaces often appear to be shiny.
flowers are produced individually (rare in clusters) from the axils of
the leaves. The pedicels of the flowers are
up to ¼" long. Each flower has 5 yellow petals, a light green calyx
with 4-5 lobes, and the enclosed reproductive organs. The petals are
arranged in a pea-like floral structure, consisting of a large banner,
a pair of forward-projecting wings, and an enclosed keel. The flowers
are oriented either laterally (with erect banners) or they are held
erect (with the banners at the bottom).
The blooming period occurs from
late spring to late summer, lasting about 1½-3 months. Only a few
are in bloom at the same time. The flowers are replaced by small
seedpods consisting of two segments: the first segment is infertile and
stipe-like in shape, while the second segment contains a single
seed. The root system consists of a taproot. This plant spreads by
The preference is full or partial sun, mesic to dry
conditions, and a
somewhat acidic infertile soil where there is reduced competition from
other kinds of ground vegetation.
native Pencil Flower is fairly common in southern Illinois, while in
the rest of the state it is rare or absent (see Distribution
Illinois lies along the northern range limit of this species. Habitats
consist of upland rocky woodlands, bluffs, upland savannas, sandstone
glades, prairies, and fields. Pencil Flower occurs in both higher
quality natural areas and disturbed areas, especially where sandstone
close to the ground surface.
The flowers of
Pencil Flower are cross-pollinated primarily by bees (Robertson, 1929).
This is one of the host plants of a leaf beetle, Sumitrosis ancoroides
The foliage is highly palatable to hoofed mammalian herbivores (Banta
& Thro, 1995).
An upland rocky woodland in southern Illinois.
Because it produces relatively few flowers at the same time and it is
relatively small in size, Pencil Flower is fairly easy to overlook. It
can be distinguished from similar species in the Bean family by the
shiny veins on its leaves, stipules with beak-like ciliate tips, and
asymmetrical seedpods (a narrow infertile segment followed by a broader
fertile segment). There is some variability of this species across its
range in regards to the hairiness of its stems, the erectness of its
stems, whether flowers are produced individually or in small groups,
etc. At the present time, these are regarded as variations of a single