glade mallow

Glade mallow is a large, robust, herbaceous plant. It occurs in the United States in the Great Lakes region, and there are a few scattered occurrences in the northeast. It is sometimes cultivated as a garden ornamental. It is uncommon to rare throughout its range. It is rare in Minnesota. It is found in meadows, thickets, woodlands, and flood plains, and on stream banks, river banks, railroad banks, and roadsides. It grows under partial to full sun or in shade, in wet to moist, rich, loamy or silt-loamy soil.

Glade mallow is an erect, perennial forb that rises on one to several stems from a large, deep taproot and from creeping rhizomes. It can be 40″ to 120″ (1 to 3 m) tall, but in Minnesota it is usually no more than 79″ (2 m) in height. It sometimes forms colonies.

The stems are erect, round, and unbranched below the inflorescence. They are often coated with a whitish, waxy bloom (glaucous). They may be hairless, but they are usually sparsely covered with branched, star-like (stellate) hairs or unbranched (simple) hairs.

The leaves are alternate and small to very large, 2″ to 20″ (5 to 50 cm) long, and 2¾″ to 25½″ (7 to 65 cm) wide. The lowest leaves are very large, and they are on very long leaf stalks (petioles) that can be up to 47″ (1.2 m) in length. The leaves get progressively smaller and on shorter petioles as they ascend the stem. Petioles on middle and upper leaves are usually shorter than the leaf blades. At the base of each petiole there is a pair of leaf-like appendages (stipules). The stipules are linear and about ¼″ (7 mm) long, and they are persistent. The leaf blades are kidney-shaped to circular in outline. They are deeply palmately divided into usually 5 to 9 lobes, sometimes 11 lobes. On lower and middle leaves, the lobes are narrowly angled with straight sides along the tip. On upper leaves, they are concave along the tip. On all leaves, the sinus between the lobes is at an angle less than 90°. The upper leaf surface is green to dark green and mostly hairless. The lower surface is paler, and it may be hairless or sparsely covered with stellate or simple hairs. The margins are coarsely toothed.

The inflorescence is one or more branched clusters (panicles) at the end of each stem. At the base of each branch in the inflorescence there is a small, less than 3″ (75 mm) long, leaf-like bract. Each cluster is about 2″ (5 cm) long and wide and has numerous small flowers. Plants are dioecious, with male and female flowers borne on separate plants.

Each male flower is ½″ to ¾″ (15 to 20 mm) in diameter. It has 5 sepals, 5 petals, and 16 to 20 stamens. The sepals are light green and hairless. They are fused together at the base into a short, tube-like calyx, then separated at the tip into 5 broad teeth. The lobes are 1⁄32″ to 1⁄16″ (1.5 to 2.0 mm) long, shorter than the tube. The petals are 3⁄16″ to ⅜″ (2 to 10 mm) long, white, and widely spreading. The stalks of the stamens are fused at the base into a narrow white column, then separated at the tip into short white filaments. The anthers are tan to pink.

Each female flower has 8 to 10 styles, each with a stigma in the inner side. The stamen tube is very short and there is a ring of stalkless anthers at the top. The female flower is otherwise similar to the male flower.

The fruit is a dry compound fruit (schizocarp) that splits at maturity into 6 to 10 sections (mericarps). Each mericarp is ⅛″ to 3 ⁄16″ (4 to 5 mm) long, erect, and kidney shaped, and each contains a single seed.

40″ to 120″ (1 to 3 m)

White

Moist. Meadows, thickets, woodlands, and flood plains, and on stream banks, river banks, railroad banks, and roadsides. Partial to full sun. Rich, loamy or silt-loamy soil.

Mid-June through mid-August

Sources

2, 3, 4, 5, 6, 24, 28, 29, 30.

Native

Rare in Minnesota

Glade Mallow
I was biking the Root River Trail between Houston and Rushford, between miles 35 and 36 on the DNR map, and came across this Glade Mallow, Napaea dioica. I noticed that you didn’t have any photos of this plant.

Napaea dioica
corey.raimond

Greg Watson
7/21/2024

Location: Root River State Trail

I was biking the Root River Trail between Houston and Rushford, between miles 35 and 36 on the DNR map, and came across this Glade Mallow, Napaea dioica. I noticed that you didn’t have any photos of this plant.