However they do not live in the higher elevations - when driving up the highway and going up in elevation you can see them thinning out and pretty soon they just no longer appear as part of the high country desertscape.
Pretty much all cacti are started from seed - if a Saguaro seed lands at the base of a tree, the tree will shade the seed and when a young cacti starts growing the tree protects the seedling - however the cacti as it starts to mature will kill the tree and will rob the tree of its water - they can consumer a ton of water and most every thing around it dies.
:>) JR
