halberd-leaf rosemallow

Halberd-leaf rosemallow is a large, showy, herbaceous, flowering plant. It occurs in the United States from New Jersey to northern Florida, west to South Dakota and eastern Texas. It is uncommon in Minnesota. It is found in marshes and swamps; in low areas along rivers and streams; on islands in rivers, streams, and ponds; and in roadside ditches. It grows under full or partial sun in wet fertile soil. It frequently forms large colonies.

Halberd-leaf rosemallow is a 2½′ to 6½′ (80 to 200 cm) tall, erect, perennial herb that rises on a single stem from a taproot.

The stem is erect or ascending and round. It may be unbranched or sparingly branched, and it may be hairless or almost hairless. It is often somewhat covered with a whitish, waxy film (glaucous), and it is sometimes slightly woody near the base.

The leaves are alternate, 2⅜″ to 7″ (6 to 18 cm) long, and 1 3⁄16″ to 6¼″ (3 to 16 cm) wide. They are on leaf stalks (petioles) that are half as long as the blade or somewhat longer. The leaf blade is narrowly to broadly egg-shaped in outline. It is heart shaped to straight across (truncate) at the base, and it is narrowed to a point at the tip with concave sides along the tip (acuminate). It is usually arrow-shaped, shallowly to deeply 3-lobed at the base but with the lateral lobes turned outward rather than downward (hastate). The middle lobe is triangular and is much longer than the lateral lobes. The leaf is said to resemble a medieval halberd, and this is the feature that gives the plant part of its common name. Some leaves may have 5 lobes and resemble a maple leaf. Some leaves may be unlobed and lance shaped or egg shaped. The upper and lower surfaces are hairless. The margins are relatively finely sawtoothed (serrate). There is a pair of awl-shaped, leaf-like appendages (stipules) at the base of the blade, but these are shed during the leaf’s development.

The inflorescence is solitary flowers in the axils of the upper leaves and occasionally at the end of the stem. Each flower is on a jointed, ⅜″ to 4″ (1 to 40 mm) long stalk (pedicel). Beneath each flower head there are 9 to 15 modified leaves (bracts). The bracts are conspicuous, ⅜″ to 1 3⁄16″ (10 to 30 mm) long, linear, upwardly curved, and hairless. The flowering period in Minnesota is August to September. Each flower lasts just a single day.

The flowers are broadly funnel shaped and very large, up to 5″ in diameter. There are 5 outer floral leaves (sepals), 5 petals, numerous stamens, and 5 styles. The sepals are fused at the base into a 1″ to 1⅜″ (25 to 35 mm) long, hairless, narrowly bell-shaped cup (calyx), then separated into 5 broadly triangular lobes. The petals are usually pink, sometimes white, and they usually have a dark reddish-purple base. They are inversely egg shaped, 2″ to 3″ (50 to 80 mm) long, and 1″ to 2″ (25 to 50 mm) wide. The stalks of the stamens (filaments) are fused from the base into a straight, pale pink to white, 1″ to 1½″ (25 to 40 mm) long column. They are separated for just 1⁄16″ to ⅛″ (2 to 4 mm) at the top. The styles are fused for most of their length into an upwardly curved tube, then separated into 5 branches at the tip. Each branch has a globe-shaped or disk-shaped, pale pink to white stigma at the tip.

The fruit is a brown, egg shaped, 11⁄16″ to 1 3⁄16″ (18 to 30 mm) long capsule with 60 to 90 seeds. The capsule is completely enveloped in the persistent calyx, which has become about 1 9⁄16″ (40 mm) long. The enveloped fruit is subtended by the persistent, upwardly curved bracts.

2 ½′ to 6 ½′ (80 to 200 cm)

Pale pink to white

Wet. Full or partial sun. Marshes; swamps, roadside ditches, and along rivers, streams, and ponds.

August to September

Sources

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

Native

Uncommon in Minnesota

I noticed that you don’t have a listing for the Halberd-leaved Rose Mallow, Hibiscus laevi.

The pictures were taken on the trail around Lake Winona, in Winona, MN.

Greg Watson
8/16/2024

Location: Winona, MN

I noticed that you don’t have a listing for the Halberd-leaved Rose Mallow, Hibiscus laevi.

The pictures were taken on the trail around Lake Winona, in Winona, MN.