Cephalocereus senilis (old man cactus) is a species of cactus native to Guanajuato and Hidalgo in eastern Mexico. It is threatened in the wild, but widespread propagation and popularity in cultivation have reduced the demand on wild populations.

Cephalocereus senilis is a tall, columnar species with clusters of stems that may grow to 5–15 m tall; the individual stems are usually unbranched, being unable to withstand the weight of side branches adequately. The most striking feature is the shaggy coat of long, white hairs suggestive of unkempt hair on an old man. The coat is a particularly striking silvery white on the young cactus; as the plant ages the stem begins to lose its covering. The flowers are red, yellow, or white, though the plant may not flower until 10–20 years old.

• EXIF Data

• Camera Type: NIKON D3100
  
  Lens: 18.0-55.0 mm f/3.5-5.6
  
  Date Taken: 2/22/13
  
  Aperture: f/5.6
  
  Shutter Speed: 1/60
  
  ISO: 100
  
  Exposure Mode: Manual
  
  Focal Length: 18.0 mm
  
  White Balance: Manual
  
  Metering Mode: Center Weight
  
  Light Source (In Camera): N/A
  
  Flash: N/A 
  
  Light Source (External): Late afternoon cloudy weather
  
  Size: 709 KB
  
  Location: 4361 Custis Avenue, Sacramento, California
  
  Latitude: 38,32.7424N
  
  Longitude: 121,29.8172W
  
  Elevation: 7.70 m