Description: This native perennial plant is about
1½–2½' tall, branching occasionally. The upper stems are
light green and pubescent, while the lower stems are often brownish green and
coarsely hairy. These stems
are round in circumference, rather than angular. There
are a few basal leaves (produced during the spring) and alternate cauline
leaves. The lower cauline leaves are trifoliate, while the upper cauline leaves
are usually simple; they are rather irregular in shape. The simple leaves and
leaflets of the compound leaves are up to 4" long and 3" across, becoming
smaller as they ascend the stems. They are lanceolate to oval-ovate, coarsely
serrated, and often cleft into 3 major lobes. Their margins are often shallowly
cleft or incised as well. The basal leaves are similar to the cauline, except
that they are always compound (either trifoliate or odd pinnate). The wrinkled
upper surface of each leaf is either hairless or has scattered hairs that are
very short and bristly; the lower surface is either hairless or has a few hairs
along the major veins. The lower leaves have stout petioles up to 1" long,
while the upper leaves have short petioles or they are sessile. At the base of
each petiole, there are a pair of leafy stipules up to ½" long that are
usually toothed along their margins. Each upper stem often terminates in 1-3
flowers; sometimes individual flowers are produced from the axils of the upper
leaves. Each peduncle (flowering stalk) bears a single flower; this peduncle is
up to 3" long and finely pubescent. Each flower is about ½" across,
consisting of 5 bright white petals, 5 triangular green sepals, and numerous
stamens surrounding a cluster of green carpels with elongated styles. The
sepals are the same length or shorter than the petals; they are initially
spreading, but curve downward with age. The anthers of the stamens are
initially white, but they soon turn brown. The receptacle of each flower (the
surface underneath the carpels) is pubescent. The blooming period occurs during
the summer and lasts about 1-2 months. There is no noticeable floral scent.
Each flower is replaced by a spheroid cluster of achenes with persistent styles
that are hooked at their tips. This fruiting cluster spans about ¾"
across; it is initially green, but eventually turns brown. The root system
consists of a taproot and rhizomes; from the latter, vegetative offsets can be
produced. This plant occasionally forms colonies.
Cultivation: The preference is light shade or
partial sun, moist to slightly dry conditions, and a loam or clay-loam soil. At
favorable sites, this plant can spread aggressively and is somewhat weedy.
Range & Habitat: White Avens is
a common plant that occurs in every county of Illinois (see
Distribution
Map). Habitats include mesic deciduous woodlands, woodland borders,
thickets, partially shaded seeps,
fence rows with woody vegetation, powerline
clearances in wooded areas, and edges of yards. Sometimes White Avens can be
found in disturbed meadows and tall-grass prairies, but this is atypical. It
adapts well to disturbed areas.
Faunal
Associations: The flowers attract various insects, including bees,
wasps, flies, and beetles. These insects suck nectar; some bees also collect
pollen, while Syrphid flies often feed on the pollen. Apparently the foliage of
White Avens is not attractive to mammalian herbivores; it is not often grazed
by White-Tailed Deer. The hooked achenes can cling to the fur of mammals,
feathers of birds, and clothing of humans; by this means, they are distributed
far and wide.
Photographic Location:
The upper photograph was taken near a powerline clearance at Busey Woods in
Urbana, Illinois, while the lower photograph was taken at a tallgrass prairie
of Meadowbrook Park in the same city.
Comments: The flowers of White Avens resemble those
of various Rubus spp. (Blackberries), except that they are a little
smaller. The structure of its flowers is typical of many species in the Rose
family. This is probably the most common Geum sp. (Avens) in Illinois.
In general, White Avens can be distinguished from other species of Avens by its
bright white petals, which are as long or longer than the sepals. Its lower
cauline leaves are trifoliate, whereas the lower cauline leaves of other
species of Avens are often oddly pinnate with 5 or more leaflets. In
particular, Geum laciniatum (Rough Avens) resembles White Avens and
occurs in many of the same habitats. However, the petals of its flowers are
shorter than the sepals. The flowering stalks of White Avens are finely
pubescent, while the flowering stalks of Rough Avens have coarse spreading
hairs. Another species, Avens virginianum (Pale Avens), is restricted to
southern Illinois. The petals of its flowers are cream rather than bright
white, and they are substantially shorter than the sepals. Unlike White Avens,
its lower cauline leaves are often odd-pinnate with 5
leaflets.