Opuntia humifusa (Raf.) Raf.
Opuntia calcicola Wherry
Opuntia compressa auct. non J.F. Macbr.
Opuntia compressa J.F. Macbr. var. allairei (Griffiths) D. Weniger nom. nud.
Opuntia compressa J.F. Macbr. var. fuscoatra (Engelm.) D. Weniger nom. nud.
Opuntia compressa J.F. Macbr. var. microsperma (Engelm. & Bigelow) L.D. Benson
Opuntia cumulicola Small
Opuntia humifusa (Raf.) Raf. var. humifusa
Opuntia rafinesquei Engelm.
Eastern Prickly Pear
Eastern prickly pear is widespread in eastern North America. I first encountered these in an outdoor botanical garden in Massachusetts (I have since seen them on sandy soil in urban environments), and I was amazed to learn that there are cacti that grow that far north.
Plants: These cacti form low shrubs, sometimes lying very close to the ground and looking rather unhealthy. Oval stem segments resembling Mickey Mouse ears are green to red-purple, 1½-4" (4-10 cm) by 1½-2" (4-6 cm), and about ⅜" (1 cm) thick. Only the upper areoles have spines, which are gray or brownish and ¾-1¾" (2-5 cm) long. (Sometimes there are no spines.)
Flowers: Yellow flowers are up to 1" (3 cm) in diameter. The purplish or reddish fruits, called tunas, are ½-1½" (1.5-4 cm) long.
Fruits: Mature fruits are 1½-2" (3.8-5 cm) long and ½-¾" (1.3-1.9 cm) across, dull red to reddish brown, and oblanceoloid-oblongoid in shape.
Edibility: The egg-shaped fruits are edible, and taste a little like watermelon.
Opuntia humifusa at Illinois Wildflowers
Opuntia humifusa on floridata.com
Opuntia humifusa on the USDA Plants Database
Opuntia humifusa on the USDA Forest Service's Fire Effects Information Database
Opuntia humifusa on the Virginia Tech Weed Identification Guide
Opuntia humifusa at the Lady Bird Johnson Wildflower Center
Opuntia humifusa on Wikipedia
Opuntia humifusa on the Connecticut Botanical Society's Connecticut wildflowers site
Opuntia humifusa on eFloras
Opuntia humifusa description by Thomas H. Kent, last updated 12 Oct 2018.