HEGEWISCH — Chicago's last wild cacti reside in a smidgen of space in the city's extreme far Southeast Side.

There are less than 100 eastern prickly pear cacti left inside less than an acre of land in an isolated area of the 183-acre Powderhorn Prairie Marsh Nature Preserve in Hegewisch.

The preserve, surrounded by industrial plants and train tracks, holds some of Chicago's rarest animals, including nesting osprey, and hard-to-find flora, including the cacti.

"Most people tend to be surprised that they're out there and surprised that we have cactus in Illinois. I certainly was when I found out," said Dan Spencer, a resource ecologist with the Forest Preserves of Cook County, which oversees Powderhorn.

The eastern prickly pear cactus, Opuntia humifusa, in bloom in the Dune Country Garden at Sand Ridge Nature Center in South Holland. This plant blooms in early to mid-June. View Full Caption Forest Preserves of Cook County

The sandy soil in certain parts of Powderhorn, which consists of high ridges and low swales, is ideal for cacti, which also need consistent exposure to sunlight. The plant's paddles (leaves) are a few inches long that bloom yellow flowers in early June and late July and produce a red prickly pear fruit, for which it's named.

Chicago's harsh winters don't bother the cacti. The lakefront used to be covered with the plants, but industry and agriculture wiped them all out with the exception of the precious few at Powderhorn.

"Most of this site has never been touched by a plow or grazed over for years by livestock, and it hasn't been developed," Spencer said. "It gives us a little bit of a snapshot ... of what conditions would have been like before European settlement."

Powderhorn, which was created from land purchases in 1919 and 1920, is popular with fishermen who take advantage of its lake. The nature preserve is maintained by the forest preserve and a host of volunteers, but even many of them don't know where the cacti are.

Spencer did not want to reveal the exact location because poachers might swipe the cacti, which are a food source and high in Vitamin C.

"Thankfully that hasn't happened yet," Spencer said.

Spencer believes Powderhorn's cacti will survive because of their semi-secret locale and the fact the Forest Preserves of Cook County might be adding surrounding land to the preserve in the near future.

"We are committed to ensuring that these natural assets are available to future generations. To that end we have consistently increased our efforts to protect and restore ecologically important and beautiful preserves such as Powderhorn Prairie," said Toni Preckwinkle, president of the Forest Preserves of Cook County.