Watch for Large Animals on Park Roads
A stray horse has wandered into the monument and has been seen repeatedly on and near the highway. Use extreme caution: Collisions with this large animal could be fatal to both to both the horse and vehicle occupants.
Organ Pipe Cactus
Our Namesake Cactus
The Organ Pipe Cactus (Stenocereus thurberi)
Organ Pipe Cactus National Monument is the only place in the United States to see large stands of organ pipe cacti, though their range extends far south into Mexico. The monument encompasses the bulk of its U.S. population. The organ pipe cactus is a wonderful example of the adaptations that cacti need to flourish in the Sonoran Desert. Like its fellow cacti and other desert inhabitants, the organ pipe is tuned to the rhythms of the sun and the infrequent rains.
Most organ pipe cactus will grow without a “nurse tree” in totally unprotected areas. It is a warmth loving species that can be found on south facing rocky slopes in the monument. This location is critical during the winter months, when severe frosts can actually kill the entire cactus. Sub-freezing temperatures will kill young tissue at the end of the stems. When growth begins again, the results are indentations, or the appearance of circular waves on the organ pipes. Bumpy or wavy pipes are a record of previous battles with unusual cold. As a result, the range of the organ pipe cactus is limited by frost and freezing temperatures. In the summer it protects itself from heat and water loss by storing large quantities of water in its pulpy flesh, using a unique photosynthesis pathway, having a water proof skin, and shading itself with its sharp spines.
Organ pipe cactus originated in the warm, dry tropics. When the global climate warmed at the end of the last Ice Age, the cactus slowly began migrating further north. It arrived in the Sonoran Desert only about 3500 years ago.
Organ Pipe Cactus can live to over 150 years in age, and will only produce their first flower near the age of 35. Organ pipe cactus will bloom in May and June, opening its white, creamy flowers only at night. Flowers will close up again by mid-morning, and very rarely remain open into the afternoon. This leaves very little time for daytime pollinators to feast on the sweet flower nectar. Lesser long nosed bats do most of the night pollination, and over the centuries, have developed a unique relationship with these cactus.
The fruit of the organ pipe ripens just before the summer rains and splits open to reveal a bright red seed-studded pulp. These seeds, with the aid of nurse plants or rocks, have the potential to grow from small seedlings into hundred-armed giants reaching ten to twenty feet into the air. Organ pipe cactus thrive in the Sonoran summer. High temperatures and the monsoon rains of July and August trigger the greatest cactus growth. Within the monument boundaries, an average organ pipe cactus stem grows about 2.5 inches a year.
The monument offers the best growing locations for these columnar cactus in the United States. Optimum growing conditions exist no more than a 40-50 mile radius north of the monument. Beyond this distance, conditions are not suitable. The cactus will seldom occur naturally in these areas except in very isolated locations.
Did You Know?
Kangaroo Rats are masters at desert survival. They get all the moisture they need from the seeds and plants they eat and don't need to drink any water. Their kidneys are so powerful at recycling the moisture they do get from plants and seeds, they have been known to urinate crystals. More...