Geranium family (Geraniaceae)
Description: This native annual or biennial wildflower develops ascending to sprawling stems about 1½–3' long. The stems are light green to reddish green and pubescent with short spreading hairs. Either opposite or alternate leaves occur at intervals along the stems; the leaf blades are up to 3" long and 3" across and deeply cleft into 3-5 palmate lobes. The leaf margins are sparingly dentate or further divided into small secondary lobes. The upper leaf surfaces are medium green and hairless (or sparingly so), while the their lower surfaces are pale green and pubescent. The petioles are light green and pubescent. At the base of each petiole, there is a pair of small linear stipules. From the axils of the middle to upper leaves, clusters of 2 or more flowers develop on slender pubescent stalks; these stalks are about ¾–1½" long at maturity.
Each flower is about 1/3" across, consisting of 5 light pink petals, 5 green sepals, 10 stamens, and a pistil. Fine pink lines radiate from the throat of each flower. The petals are oblong in shape and slightly notched at their tips. The sepals are lanceolate to ovate and pubescent; each sepal has an awn-like tip about 1.5 mm. long. The blooming period occurs during the summer and lasts about 2 months. Usually, only a few flowers are in bloom at the same time. Each flower is replaced by a narrow columnar fruit about ½–¾" long that tapers to a short beak. At maturity, the fruit splits open into 5 slender sections from the bottom, remaining connected together at the apex. By this process, the seeds are mechanically ejected from the mother plant.
Cultivation: The preference is partial sun, mesic to dry-mesic conditions, and cool to warm summer temperatures. Different kinds of soil are tolerated, including those that are sandy or rocky.
Range & Habitat: Northern Cranesbill is restricted to NE Illinois, where it is rare (see Distribution Map). This species is state-listed as 'endangered.' Illinois lies at the southern range-limit of this boreal wildflower. Habitats include woodland openings, sandy Black Oak woodlands, typical and sandy savannas, and rocky outcrops. This wildflower becomes more abundant after a wildfire; there is some evidence that its seeds germinate in response to heat and/or light.
Faunal Associations: The flowers are pollinated by small flies (particularly Syrphid flies) and small bees (particularly Halictid bees). Both nectar and pollen are available as floral rewards to such visitors. One insect that sucks on the juices of Geranium spp. is Macrosiphum geranii (Geranium Aphid). The seeds of some Geranium spp. are eaten by such birds as the Mourning Dove and Bobwhite Quail to a limited extent.
Photographic Location: A nature preserve in Cook County, Illinois. The photographs were taken by Lisa Culp (Copyright © 2009).
Comments: This is one of several annual or biennial Geraniums (Geranium spp.) in Illinois. The majority of these species have been introduced from Eurasia, although some of them are native. All of these species have relatively small flowers, palmately cleft simple leaves (see exception below), and a sprawling to ascending habit. As a result, they can be difficult to distinguish from each other. Northern Cranesbill can be identified through the following combination of characteristics: 1) It produces small flowers (about 1/3" across) in clusters of 2 or more, 2) the stems and stalks of the flowers are pubescent with short spreading hairs, 3) the pedicels of the flowers/fruits are longer than the sepals, and 4) the sepals have awn-like tips. One aberrant species in this group, Herb Robert (Geranium robertianum), differs from the others by its leaves, which are palmately divided into leaflets with petioles.