Know Your Natives – White avens

White avens (Geum canadense) of the Rose (Rosaceae) family occurs in the U.S. from Texas to Nebraska to Montana thence to the eastern and southern borders with the exception of Florida. In Arkansas, it is found throughout the state. Habitats include lightly shaded to partially sunny, moist deciduous woodlands, woodland borders, thickets and fence rows. Favorable sites have sandy to loamy, well-drained soils. The plant, an herbaceous perennial, consists of a thick mat of near-surface fibrous roots with a small caudex from which leaves and stems grow. Plants in bloom are 2 to 2 ½ feet tall.

Leaf appearance of white avens is variable. Basal leaves appear in early winter as a dense, ground-hugging rosette with the rosette expanding throughout winter as leaves grow and more leaves are added. Basal leaves are a blended combination of white, purple and green with lighter colors along veins. Basal leaves are pinnately compound with long peitoles and three or more leaflets. For early winter leaves, terminal leaflets are rounded and significantly larger than lateral leaflets which are of variable shape and size. Compound basal leaves of mid-winter have terminal leaflets that are more triangular with lateral leaflets becoming larger and more uniform. Leaf margins of the entire plant vary from coarsely serrate to shallowly to deeply cut. Leaf surface may be hairless to slightly hairy.

White Avens - Geum canadensePhoto 1: Basal leaves grow throughout the winter to reach their maximum size by late winter.

In spring, multiple leafy stems emerge from the dense basal rosette. Cauline (stem) petioled leaves are light green with lower leaves being alternate and trifoliate. Upper cauline leaves, on short petioles, become smaller and eventually simple and sessile toward the apex of the stem. A pair of toothed stipules, up to ½ inch long, occurs at the base of petioles of cauline leaves.

White Avens - Geum canadensePhoto 2: In early spring, multiple stems emerge with cauline leaves that differ significantly from basal leaves.

White Avens - Geum canadensePhoto 3: Shape of leaves transitions from complex winter leaves (far left) to more simple cauline leaves (left to right). Stipules are persistent.

Forming the inflorescence, stems divide into a small number of widely spaced peduncles about 3 inches long which further divide into shorter pedicels terminating with single flowers so that loose cymes are formed. Individual flowers may also develop from axils of cauline leaves. White avens flowers, maturing in mid-spring into summer, have triangular sepals that form a pointed bud with an enlarged base. Flowers open in a scattered sequence over a month or two. The half-inch wide flowers have five white, rounded petals interspersed with green, pointed sepals. Petals and sepals are about the same length. A clustered ring of many stamens with nodding whitish anthers surrounds a center composed of thirty to sixty pistils with elongated jointed styles. Sepals reflex as the flower matures. Stems are hairy, with hairs decreasing in length from bottom to top of stems. Basal leaves are usually gone by the time the plant is in flower.

White Avens - Geum canadensePhoto 4: With bloom, white avens is an open, leafy plant with long peduncles terminating in loose cymes.

White Avens - Geum canadensePhoto 5: Pointed buds with enlarged bases become flowers with rounded white petals, prominent triangular sepals and many stamens and pistils.

Late in the growing season, a half-inch round seed cluster develops from the many styles/stigmas.  At first green, the cluster and stems become brown and can persist on the plant for several months. The thin, dry, flattened 1-seeded fruits (achenes) have hooked tips allowing them to latch onto fur of passing animals (or socks of humans) for dispersal. Colonies may form from seed about a parent plant.

White Avens - Geum canadensePhoto 6: The number of seed clusters on a plant is relatively small, but each cluster consists of numerous seeds.

In a garden setting, this prolific self-seeder may become too numerous unless seeds are removed before maturity. However, it is an attractive plant year-long. Flowers are used by various bees, wasps, flies and aphids.

Two other species traditionally treated within the genus are found in Arkansas; namely, spring avens (Geum vernum) and cream avens (Geum virginanum), although barren-strawberry (Walsteinia fragaroides), a rare plant in Arkansas known only from a few north-central sites, has recently been transferred to Geum by some authorities. Spring and cream avens are both limited mostly to the Ozarks, with a few upland occurrences in the Arkansas Valley. Principal characteristics of both plants are similar to white avens; however, petals of spring avens are yellow and the cream to yellowish petals of cream avens are significantly smaller than its sepals.  Additionally, the seed clusters of spring avens are held above the calyx atop an extra stalk, while cream avens is generally a larger and more robust plant with significantly larger stipules.

Article and photographs by ANPS member Sid Vogelpohl

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