Clearly, all those outstretched saguaro arms aren’t for hugging. Because, ouch!
But they do give saguaros more chances to spread more seeds.
“Saguaros produce flowers at the top of their stems, so if you have a single saguaro stem they’ll produce flowers there and flowers turn into fruits and produce seeds and the seeds are what create young saguaros,” Swann says. “If you’re a saguaro and you’re doing pretty well, you can grow arms and at the end of every arm you can produce more flowers and therefore more seeds.”
Generally, saguaros have to be very mature to start producing flowers, which could happen when they’re as young as 35 years old, but is more likely when they’re in their 60s, Swann says.
While they get a late start producing flowers, it’s something they can do for the rest of their lives until they die around 150 to 200 years old.
More arms mean a happier saguaro Tucson’s quirky saguaros
It also takes a saguaro quite a while to grow its first arm, if it grows any at all.
Photo by Jeff Cardella
“There’s no hard and fast rule and there’s exceptions to everything, but generally when they’re like 75 years old they’ll start producing arms,” Swann says.
And the number of arms they grow largely depends on one thing: water.
“Since water is the primary limiting factor for them in the desert, in areas where they’re getting more moisture they tend to grow more arms,” Swann says. “As you’re hiking around you’ll notice there tends to be more arms on saguaros that are near washes, for example. So basically if the conditions are favorable and they can put that energy into reproduction (in other words if they’re getting enough water they need to survive) then they’re going to grow more arms.”
This is also why saguaros at Saguaro National Park East in the Rincon Mountains, which tends to see more precipitation, grow faster than their friends at Saguaro National Park West in the Tucson Mountains.
“The growth rate of saguaros, is directly tied to the amount of rainfall, particularly summer rain. So they’ll grow faster in wet years than they do in dry years,” Swann says.
On average, a 20-year-old saguaro is around 8½ inches tall in the west district while a saguaro growing in the east district could be around 4 inches taller, he says.
By thisistucson.com
