Handling a truly prickly 150-year-old

Me (bad pic) and mom with
saguaro and organ pipe cacti

The Desert Botanical Gardens in Arizona, is truly one of my happy places (www.dbg.org).  When we bought a home near Phoenix last year, one of my first actions was to become a member so that I could go as often as I wanted.  So Mom and I headed there last week when she was visiting.

We stumbled upon the relocation of a huge saguaro cactus into the area that will be the Gardens' new butterfly pavilion that opens up in March (yes, you can bet there will be another posting about that since I also love butterflies). 

About saguaros

Before we delve into the relocation process, a bit of background on the saguaro (carnegiea gigantic, in case you wish to refer to it by its scientific name) may be helpful. 

When you think of Arizona and the desert there, this is the cactus you likely picture -- the tall thick ones that often (but not always) have arms growing out and up.  While statistics vary on how tall, heavy and old they can be, I think it's conservative to say they can grow 40-60 feet tall,  measure 18-24 inches in diameter, weigh into the multiple ton range and grow 100-200 years old.  Surprisingly, though, they are a bit slow out of the gate in terms of growth.  There is a Rule of Thumb for the saguaros -- that a 10 year old saguaro is only about as tall as a human thumb.  A docent showed us a 12 year old saguaro that was probably only about two inches tall.  Crazy.

The saguaros only grow in the Sonoran Desert, which is primarily in southern Arizona but stretches just over the border of southern California and northern Mexico.  The combination of its two rainy seasons, generally warm temperatures and soil are key to their survival. 

With limited rainfall, it's important for the saguaro to be able to absorb as much water as possible.  It has a permanent taproot that goes directly down and is only a few feet long to, well, tap into deeper water.  It then has a network of two types of radial roots that are just a few inches under the ground that span out as wide as the cactus is tall.  There are also thread-like roots that develop when it rains to quickly soak up water and then die afterwards so the cactus doesn't have to spend precious resources maintaining them when they're not needed.

The cactus can collect up to 200 gallons of water during rainfall.  The idea that there is water sloshing around within the cactus is a myth.  The structure of the cactus is a series of ribs that are joined by various fleshy materials that store the water in their cells.  When it rains, the ribs and the cell structures of the flesh can expand to accommodate more water, adding as much as 20-25% to girth of the cactus -- kind of like an accordion file.

Like any good cactus, it has sharp spines.  There is more to the large spines than protecting the cactus from being eaten/destroyed by large animals.  They have other functions as well, including directing rainwater to depressions in the cactus, cooling the skin of the cactus, insulating the cactus and re-directing wind.

If you see most saguaros, they have holes in them.  These are generally homes for birds and small animals.  The gila woodpecker usually starts the holes, carving out a space within the fleshy parts.  The cactus responds by forming a sort of scar tissue that protects the cactus from water loss and also creates a hard shell to define the woodpecker's nest.  Other animals like mice move into abandoned woodpecker nests.

The cactus flowers from roughly April through June, opening up at night and closing during the midday heat. (In case you're curious, the saguaro's flower is the state flower of Arizona.)  Fruit develops later if the flowers were pollinated.  It's estimated that each fruit contains about 2,000 seeds.  For a variety of reasons, though, few survive to become a seedling and fewer still to adulthood.

One other structural note.  If you ever see a saguaro with its arms hanging down, this is a result of frost.  If there is a severe frost and the cactus starts to freeze, the "joints" of the arms are impacted first and cannot sustain their structure and thus droop.  While they may survive and the ends of the arms may start growing upward, the initial droop remains.  Obviously, if the frost is severe enough, the entire cactus may die.

Moving saguaros

Due to challenges in reproduction and the growing black market for saguaros, legal protections have been put in place at the federal level as well as in Arizona that govern the harvesting, collecting or destruction of them.  For example, a developer in Scottsdale can't just bulldoze saguaros, but generally has to replant or give them away.  Companies can obtain tax deductions for donating them to organizations like the Desert Botanical Gardens, for example.

Moving them is not easy, though.  First of all, how do you approach something that has large spikes all around it?  How do you transport something that weighs tons?  How do you ensure that it will survive when you're only taking a fraction of its root structure that has taken, oh, say, 100 years to build?

Not surprisingly, a cottage industry has emerged to address the need.  While I didn't get to see the preparation, it seems that they dug out a root ball that is large enough to capture the taproot.  They wrap carpets around certain spiny parts where they need to access or secure the cactus, including creating wooden structures to support the arms during transit and to create space among the arms during transport so they're not crushed.  The cactus is then attached with industrial-size ratcheting tie-downs to a specially-designed boom truck.

At the relocation site, the process is reversed as you can see in the photos below.  What's important to note is that the cactus must be situated in the precise direction relative to the sun as it was in its original location.  It also needs to be supported by braces for a while until it begins to rebuild its root structure.  Because it doesn't have a root structure sufficient to support such a large plant, professional attention is required to determined the best way to keep the cactus hydrated and to develop the root system.

I've named this replanted saguaro Sonny and can't wait to visit her the next time I'm back at the DBG.

Sonny on the truck, being moved into position and raised, protective structures removed and, finally, in place