Copy shortlink: For centuries, the wild grasslands and valleys of Minnesota were dotted with a type of cactus, spiky and round, that blooms every spring. It grows about ankle high, roughly the size of a softball, and sprouts a violet or hot pink/fuchsia flower with a golden center. It survives almost exclusively on top of granite, growing on the large stones and outcroppings that jut out of the state's scattered prairies and wetlands. Now, arborists warn, it needs saving — quickly. The threatened species has lost all but two of its largest populations in the state. Both of those surviving clusters of cactuses, unfortunately, are in active granite quarries, said David Remucal, curator of endangered plants for the University of Minnesota Landscape Arboretum.