The large genus Opuntia includes prickly pear and beavertail cacti, both of which have stems
that resemble paddles, many oval pads ½-1" (1.3-2.5 cm) thick. Cholla used to be considered
Opuntia as well, but they have been reclassified as members of Cylindropuntia.
Botanists disagree as to whether Cylindropuntia should be a separate genus or a subgenus
of Opuntia.
This table compares some members of Opuntia.
(Opuntia) · 7/11/1999 · Florissant and Lake George area, Colorado · By Tim Chandler Species not yet identified
These plants are 4-12" (10-30 cm) high, lying or growing close to the ground.
Less than 24" (60 cm) high, spreading into wide clumps with hundreds of pads.
Up to 6' (1.8 m) high, usually lower; in spreading clumps up to 10' (3 m) wide.
Flowers
Yellow or pink, 1¾-3" (5-7.5 cm) in size.
Dark pink, with a yellowish center; also yellow, peach, or salmon-colored.
Yellow to red.
Leaves
Glochids are tan or brown, ⅛" (3 mm) long. There are no spines unless it has introgressed with other species.
Typically without spines, but may have short yellow spines. Spine clusters occur in diagonal rows of 10-16 across each pad.
Spines are 1-1½" (2.5-3.8 cm) long, in groups of 1-6, groups about 1½" (3.8 cm) apart. No spines or very short spines, spines are chalky white, sometimes yellow.
Stem
Stem segments are ellipse- or egg-shaped, 1¾-4" (5-10 cm) × 1-2" (3-6 cm).
Pads are blue-gray, up to 7" (17 cm) long, ½-¾" (1.3-1.9 cm) thick.
Thick yellowish- or bluish-green pads up to 10" (25 cm) long, less than 1" thick.
Fruit
½-⅞" (1.5-2.5 cm) in diameter, green, without spines.
Egg-shaped, purplish-green
Barrel-shaped, initially yellow-green, ripening to purple, up to 3" (7.6 cm) long. No spines or very short spines, spines are chalky white, sometimes yellow.
Up to 8' (2.4 m) high, usually lower; in spreading clumps up to 10' (3 m) wide.
Low, usually prostrate.
Up to 4' (1.2 m) tall. Pads are purple or purple-tinged green.
Flowers
Yellow to red. About 2-3" (5-7.6 cm) across.
Yellow. 2-3" (5-7.6 cm).
1 to 8 yellow flowers with red centers, along the tops of pad. Flowers are 2-3" (5-7.6 cm) in diameter. By Jodelet/Lépinay.
Leaves
Spines are 1-1½" (2.5-3.8 cm) long, in groups of 2-6 (usually 3-5), groups about 1½" (3.8 cm) apart. No spines or very short spines, spines are light yellow.
Spines may only occur on top portion of pads. 1-4 spines per group. Somewhat flattened, brown or white, often darker at the base.
Sometimes has no spines, or groups of up to 15. Spines are up to 7" (17 cm) long! Longer spines are reddish brown to black (or rarely, yellow to red), turning whitish with age.
Stem
Thick yellowish- or bluish-green pads up to 10" (25 cm) long, less than 1" thick.
Fruit
Barrel-shaped, initially yellow-green, ripening to purple, up to 3" (7.6 cm) long.
Fruit is deep maroon or purple, oval or barrel-shaped, without spines.
Forms spreading colonies up to 15' (4.6 m) across.
Up to 7' (2.1 m) high, may have a short trunk.
Flowers
Bright yellow with pale red centers, peach-colored, pinkish, or reddish. Up to 3" (7.6 cm) wide.
Lemon yellow, becoming more orange as they age. Flowers occur on tops of pads. Photo by Stan Shebs.
Leaves
Spines are brown, reddish brown, or gray, up to 1½" (3.8 cm) long. Pads and fruit also have tiny hairlike spines that detach easily and are difficult to remove from skin.
Pads are 4-8" (10-20 cm), tinged with purple; turning entirely purple when very dry. Spineless, or pink or reddish spines less than 1½" (3.8 cm) long. There are also tiny reddish-brown, loosely attached spines called glochids, which are irritating and difficult to remove.
Fruit
Fruits are red or purple, up to 2" (5 cm) long.
Barrel-shaped. Smooth. About 1" (2.5 cm) x 1½" (3.8 cm).
Species not yet identified 
