In hikes around the desert behind the RV park, there is the opportunity to see the nurseries for these Sonora desert giants. The saguaro seed is about the size of a poppy seed. For this seed to develop to maturity, requires a protected environment. Since the sprouting seed and the very young plant needs water, the seeds that fall in the shade of a desert tree or bush has a better chance of survival.
Other than the four small saguaros visible in this photo, there are some that are the size of a finger tip.
Noting the smaller nurseries, in one of my hikes I found a nursery with eleven saguaros. They are not all visible in this photo, but after several counts the total came to eleven.
On another hike, I found an even larger nursery. Once again, it is difficult to see all of them from the location where the photo is taken. A younger group of saguaros in this very dense palo verde, some of the less visible specimens were less than a foot tall. This was a record in my searching. There were 17 in this nursery.
On another hike (a cloudy day), found this nurse tree surrounded by saguaros. One towering over the nurse.
There are times that the nurse tree will have died. Speculation is that the saguaros take the water and nutrients which will cause the nurse tree to die.
"There are some who can live without wild things and some who cannot." -- Aldo Leopold
For a brief overview of the saguaro, see Saguaro Cactus brochure from the National Park Service at Saguaro National Park.