plains prickly pear

LC - Least Concern

N5 - Secure

S3 - Vulnerable

Special Concern

Plains prickly pear is a low, succulent, spiny, perennial shrub that rises from tuberous, somewhat woody roots. It usually forms a 3″ to 6¼″ high mound but may also form a 24″ to 60″ in diameter mat.

The stems are prostrate or spreading, branched, and often divided into 2 or 3 segments (pads). The pads are not easily detached. If broken apart, the separated segment can send down new roots and form a new plant.

Each pad is greatly flattened, egg-shaped to circular, 2¾″ to 4¼″ long, and 1⅜″ to 3″ wide. It is dark green, dull, and hairless. It is covered with a thick, waxy skin. It is usually fleshy and usually smooth but may become flabby and wrinkled with the approach of winter or when stressed.

On the surface of each pad are a number of woolly patches (areoles). Areoles are actually extremely short modified branches. They are widely spaced, mostly ⅜″ to 1¼″ apart, and are arranged in diagonal rows. The row at the widest part of the pad has usually 5 or 6, sometimes 7 or 8, areoles.

Each areole is oval to circular and 1 ⁄16″ to ⅛″ in diameter. It is covered with a dense tuft of numerous 1 ⁄16″to 3 ⁄16″ long barbed hairs (glochids). The glochids are pale yellowish-brown or tan at first, becoming brown as they age. They have minute downward-pointing barbs and are easily detached. All areoles usually also have 1 to 4 true spines. Spines are denser toward and on on the margins of the pad. The spines are white to reddish-brown, straight, needle-shaped, stout at the base, erect to spreading, and ⅜″ to 2¼″ long. They are round or only slightly flattened on cross section. They are not easily detached.

The inflorescence is 1 to several flowers rising singly from areoles on the margin of the pad. The flowers are broadly funnel-shaped, 2″ to 3″ in diameter, and showy. There are 3 petals, 3 petal-like sepals (6 tepals), numerous stamens, and 1 style. The tepals are tepals are 1″ to 1½″ long, the outer tepals shorter than the inner. The outer tepals are egg-shaped and green at the base grading to yellow at the margins. The inner tepals are inversely egg-shaped to spoon-shaped and have an abrupt, short, sharp point at the tip. They are mostly yellow but usually tinged with orange or red at the base. The stamens have long slender filaments and small yellow anthers. The style is stout and has 4 to 9 stigma lobes.

The fruit is an elongated, inversely egg-shaped, 1″ to 1½″ long, ⅝″ to 1⅛″ in diameter berry with numerous seeds. It is fleshy, juicy, hairless, and green at first, becoming dull red or purple when ripe. The fruit has glochids, sometimes restricted to the upper margin, but no spines. It matures from mid-July to mid-September. It is edible.

3″ to 6¼″

Yellow

Dry. Prairies, dunes, lakeshores. Rocky or sandy soil. Full sun.

Mid-June to July

Sources

2, 3, 4, 5, 6, 7, 28, 29, 30.

Native

Common

According to the Minnesota DNR’s Rare Species Guide there is disagreement as to which species of Opuntia, O. humifusa or O. macrorhiza, occurs in Minnesota, but there is agreement that only one does. The Bell Herbarium at the University of Minnesota reports all collected specimens as eastern prickly pear (O. humifusa). Some authorities use the Bell Herbarium as one of their sources or their only source of species distribution in the state. BONAP shows only O. humifusa in the state. USDA PLANTS shows both species occurring in the state with similar distributions. The DNR shows only O. macrorhiza occurring in the state.

According to FNA, O. macrorhiza inner tepals are red at the base while those of O. humifusa are yellow throughout. The photos on the DNR’s Rare Species Guide, and photos on MinnesotaSeasons.com, show a flowers with red at the base of the inner tepals, making them clearly O. macrorhiza.

Plant

Flowering Plant

Fruiting Plant

Inflorescence

Flower

Young Pad

Mature Pad

Infructescence

Fruit

Spines