Some love it as a plant they know in its proper habitat-a native plant in deserts of North and South America, or as a crop for the cultivation of cochineal insects for their red dye, or simply as an exotic potted plant that is carefully tended in climates unsuitable for its growth. In many countries around the world it is hated as a weed- a plant that can grow uncontrollably fast in places where it has been imported.Prickly pear plants are made up of pads joined together, which are actually flattened stems. The only leaves are small, short-lived fingers that cover the new, expanding pads in spring. Scattered over the mature pads are areoles from which long spines, and fine brown bristles, or glochids, grow. Each areole is also a growing point from which a new pad, flower, or root can develop. Any pad broken off and allowed to lie on the ground will put down roots when it rains and soon become a new plant. In this way prickly pear can spread fast.I sat one November day in Montrose Canyon near Tucson. It had been hot and dry for months. The pads of prickly pear were thin and wrinkly; diamond shapes between spines, rows of ridges like ripples on a sand bar. They looked old, for surely wrinkled means old. But they were mostly not old. With winter rain they would swell and fatten, swell out and become smooth with no sign of wrinkles. Not many living things rejuvenate themselves like cactus pads, though they cannot regain the tiny little pinky-green fat fingers that were leaves. I thought how, inside those wrinkled pads, there was still moisture, waiting, storing life inside those wrinkled green skins, and marveled at the adaptation to drought conditions that occur in southern Arizona before and after the short-lived summer rains.Although there are hundreds of species of prickly pear, varying from miniature plants to trees one hundred feet tall, the common ones are wide, spreading shrubs about four feet high, with their pale, gray-green rounded pads about nine inches long. The Englemann's prickly pear (Opuntia englemannii) is one of the commonest, with its long white spines and rusty colored glochids. Looking across the sun-bright desert of Arizona, patches of round, clumped pads in their faded watercolor-green, between giant saguaros and Palo Verde trees, is the classic Sonoran desert scene. Or, looking at a steep rocky slope from a distance, one sees, between the giant saguaros, the regular patches of rounded pads, their smooth hard surfaces reflecting sunlight at different angles, those in shade enhancing the green of their sunlit neighbors by their contrast. No other place in the world resembles the deserts of southwest North America.It rains. The muted greens of cactus plants seem brighter without sun and drops roll off the prickly pear pads to darken the desert pan. Moisture causes the strange fragrance of creosote bushes to pervade the atmosphere. Cottontail rabbits have taken cover and no birds sing. Rain is such an event in the desert, and through the melancholy air I watch the gentle fall of contentment. This winter rain will make a colorful spring. The pads of prickly pear are swelling, the wrinkles of drought ironing out as the masses of fine roots absorb water. Those fine roots take up the merest suggestion of water, roots that hold together the thin layer of desert soil.From every window of my house here in the Sonoran desert I see Englemann's prickly pear. As far as I can see this is the most common plant, though patches of different cacti, bur-sage, and creosote bush are intermingled, along with a wide variety of less common desert plants. The diversity is remarkable to me after having known the Sahara, where the few plants species are scattered and rare. And with this rain, the seed bank in the soil will sprout dozens more species that wait for a little more warmth to grow up and flower.How much the prickly pear will grow in the spring and how many flowers develop depends on how much rain we get this winter, and I think of April when the young soft pads swell out-the soft, bright green nopales that provide a vegetable for many, especially Native Americans. …