Description: This native perennial plant is usually about 6" tall, but sometimes reaches 1' or a little more. There is a central stem that branches occasionally, creating a bushy effect on mature plants. It is often covered with scattered white hairs. The alternate trifoliate leaves have fairly long petioles, and are about ¾" across when fully open. Depending on environmental conditions, they are light green, green, or reddish green, and fold up at night. Occasionally, they fold up in response to intense sunlight during midday.
Floppy umbels of yellow flowers emerge
from the leaf axils on long, slightly hairy stalks. Each bell-shaped flower is
about ½" across when fully open, and has 5 petals that flare outward.
There are fine lines toward the throat of the flower, which is subtended by 5
green triangular sepals. Sometimes, the throat of the flower is slightly red.
Like the leaves, the flowers close-up at night. There is little or no floral
scent. The blooming period peaks during late spring or early summer, but
continues intermittently until the fall. Plants often become dormant during the
hot dry spells of mid- to late summer. The root system consists of a slender
branching taproot with numerous secondary roots. This plant spreads by means of
mechanical ejection of the seeds from the slightly hairy elongated seed
capsules; each capsule splits into 5 sections.
Cultivation: The
preference is full or partial sun, and moist to slightly dry conditions. Growth
is best in a rich loamy soil, although poor soil containing clay, gravel, or
sand is tolerated. Yellow Wood Sorrel is a very robust little plant and will
spread, if it is given half a chance, particularly in open, disturbed
situations. It doesn't compete well against taller plants, however. Foliar
disease doesn't appear to affect this plant significantly.
Range & Habitat:
Yellow Wood Sorrel is a common plant that occurs in every county of Illinois
(see
Distribution
Map). Habitats include mesic black soil prairies, openings in woodlands,
savannas, limestone glades, pastures, lawns and gardens, powerline clearances,
edges of paths and driveways, and miscellaneous waste areas. This plant is more
common in degraded habitats.
Faunal
Associations: Flower visitors include small bees, Syrphid flies, bee
flies, small butterflies, and skippers. Among these insects, bees are probably
the most important pollinators, including such species as Ceratina dupla
dupla (Little Carpenter Bee), Calliopsis andreniformis (Andrenid
Dagger Bee), and Melissodes bimaculata bimaculata (Two-Spotted Miner
Bee). The Syrphid flies feed on pollen and are non-pollinating. Several species
of songbirds and upland gamebirds eat the seeds, including the Bobwhite,
Mourning Dove, Horned Lark, Field Sparrow, Grasshopper Sparrow, Savannah
Sparrow, and Slate-Colored Junco (winter only). The Cottontail Rabbit and
White-Tailed Deer eat this plant occasionally, even though the leaves are
slightly toxic from oxalic acid.
Photographic
Location: The photographs were taken on the grounds of the
webmaster's apartment complex in Urbana, Illinois.
Comments: This
little plant is cute-looking when covered with yellow flowers, but devalued
because of its ubiquitousness. The leaves can be added to salads in small
amounts – they have a slightly sour taste. Some authorities recognize
another species of wood sorrel, Oxalis dillenii, which also has yellow
flowers and is very similar to Oxalis stricta. The former species is
supposed to have more erect pedicels, rhizomes, and other slightly different
traits that distinguish it from Oxalis stricta. However, it seems more
likely that these are merely variations of the same species.