Description: This native perennial plant is 1-2½' tall. It consists of 1-3 levels of flattened pads, starting with a single pad on the ground. Each pad is up to 10" long, 7" across, and 1½" thick. One or two new pads may develop from the top of the original pad, providing a limited branching ability. Older pads tend to be bluish green, while younger pads are green. The pads are evergreen during the winter, but have a tendency to appear yellowish and desiccated at this time. There are several areoles scattered around each pad. A single spine (sometimes two) may develop from an areole; the spines are light grey or light brown and highly variable in length – usually 4" or less. There are also small deciduous leaves near the areoles – these are usually green and scale-like in appearance, but quickly drop from the plant.
One or more flower buds can form on the
top of a pad. They are individually up to 2" long and 1" around, green and
scaly, with a knob-like shape. Each bud produces a single flower about 3-4"
across. The flowers are satiny yellow and very showy, consisting of several
petals that surround numerous stamens with yellow anthers. Sometimes the
flowers are red or orange-red toward the center. The blooming period occurs
from late spring to mid-summer and lasts about a month for a colony of plants,
although each flower lasts only a single day. There is no floral scent. A
fleshy fruit develops that is spiny and turns yellow when mature. The root
system is fibrous, shallow, and spreading. The upper pads often break off from
the lower pads, and are capable of re-rooting in the ground. In this manner,
new plants are created vegetatively. 
Cultivation: The preference is full sun and dry
conditions. This plant will tolerate average amounts of moisture and a little
shade. Poor soil that is rocky or sandy is preferred, although loamy soil is
also tolerated if it is reasonably well-drained. Older stems on the ground have
a tendency to become brown and woody with age, which is natural. It is faster
and easier to start new plants using pads, rather than seeds; they form new
roots readily. This is the easiest cactus to grow in Illinois because of its
greater tolerance of moisture and humidity.
Range & Habitat: The Eastern Prickly Pear has
been occasionally observed in about half of the counties in Illinois (see
Distribution
Map). It is most likely to be found in sandy or hilly areas along the
Mississippi and Illinois rivers, in hilly areas of southern Illinois, and sandy
or rocky areas of northern Illinois. This is by far the most common cactus in
Illinois. Habitats include openings in sandy forests, sandy savannas, sand
prairies, gravel prairies, barrens and rocky bluffs, sandstone and limestone
glades, sand dunes, rocky or sandy slopes along major rivers and lakes, sandy
cemeteries, and pastures. Some local populations are the result of restoration
efforts or escapes from cultivation.
Faunal
Associations: Primarily bees visit the flowers (both long-tongued
and short-tongued), including Plasterer bees, Halictid bees, large Leaf-Cutting
bees,
Miner bees, bumblebees, and large Carpenter bees. Long-tongued bees suck nectar
or collect pollen, while short-tongued bees collect pollen only; the larger
bees are more likely to cause cross-pollination. In the eastern states, the
relationship of cacti to wildlife is less well-known than in the western United
States. From these western studies, it appear that the fruit and seeds are
occasionally eaten by the Wild Turkey, Striped Skunk, and Thirteen-Lined Ground
Squirrel. The fruit and stems (pads) are sometimes eaten by the Cottontail
Rabbit, White-Tailed Deer, and Coyote, notwithstanding the spines. All of these
animals occur in Illinois at the present time. The Ornate Box Turtle, which is
found in sand prairies, probably eats the fruit of Eastern Prickly Pear as
well. Those animals eating the fruits help to disperse the seeds, which can
pass through their gullets unharmed.
Photographic Location: The photographs were taken
near Kickapoo State Park in Vermillion County, Illinois.
Comments: The Eastern Prickly Pear is a striking
plant with beautiful flowers. It has fewer spines than many western species of
cactus, but they are still fairly formidable. Sometimes this cactus can form
impressively large colonies, if it persists at the same location for a
sufficiently long period of time. The only other cactus with a similar size and
appearance in Illinois is Opuntia macrorhiza (Big-Rooted Prickly Pear);
this species differs from the Eastern Prickly Pear by its thick tuberous root,
and two or more spines can appear from each of its areoles, rather than just
one. In the past, the Eastern Prickly Pear has been referred to by various
scientific names, including Opuntia compressa and Opuntia
rafinesquei.