Field of Bones
First off, let’s blow your hair back a bit:
Joshua Trees are succulents. Yes.
They’re just really really tall.
And they are not the only woody, tree-like cacti out there.
Which, in a roundabout way, leads me to the real topic of the day:
Cholla cacti have wood skeletons. After they die and the water evaporates, after the skin falls off and the desert critters move in – they leave behind some wood.
I never connected the plants as alive to how they were when dead. The dead form of it is so lovely and mysterious and austere. It dies like an animal, the innards dessicating and the skin rotting off. Finally, it’s just wood.
This just isn’t normal wood, and I love it.
This is a personal post. I am drawn to the beauty, and so I am called to learn about the plant. This is another way nature touches our lives, drawing us to learn and go deeper. Through beauty. We’re like the bee and the hummingbird.
I’ve got to appreciate nature for how it keeps me interested, keeps opening my eyes further to all the amazing, particular, unique varieties that exist even in an otherwise dead-seeming patch of hot, dry earth. I appreciate how much effort nature has put into finding this solution, and how elegant the solution is to the problems faced by this plant in this environment.
A cactus is a type of succulent. All cacti are succulents. Not all succulents are cacti.
Look for the areoles!
At the start, I just never expected a cactus to have a wood frame. I’m used to the succulents at home – puffy, happy green sacks of water, warming in the sun. None of them are particularly tall. I haven’t quite given mine the chance to stretch their legs, but they don’t have the shape or sturdiness to support that much water at that height. I was looking for trees, instead.
Looking through photos on the NPS Joshua Tree website, I came across what ended up being the right cactus. It took quite a bit more googling of dead weird wood joshua tree to finally turn it up.
So, short story long.
The cactus is called the Cholla cactus.
There are more than 20 specific species of Cholla cactus. Or rather, there’s a couple dozen species in the Cylindropuntia genus – which are each often called Cholla of one sort or another. Cylindropuntia used to be a subgenus of Opuntia (where you’ll find such things as the beavertail prickly pear), though they’ve been separated due to some differences. Cylindropuntia have cylindrical stems (Opuntia has flattened), and Cylindropuntia have sheathes on their spines (Opuntia do not).
Cholla look fairly similar on the outside – long arms covered in whitish spikes, with a great deal of surface texture. Their skeletons also look similar – thin wood tubes with many holes. Looking at the roundness of the holes and the sizes and variation of them – plus a lucky photo of one of the nearby cacti that had a similar shape and size – makes me think it’s the Cylindropuntia cholla.
Hmm. Maybe imbricata.
I could try to dig into the specific growing regions of each, knowing that I typically stick to the west side of Joshua Tree. Instead, I’ll hold off on trying to identify the exact species until I can return to the park and take a more focused look at all the nooks and crannies. More than likely, I’ve mixed up a few photos from different species growing in the same region.
It’s a cholla regardless, though. That’s more than I used to know.
The Slow Life of the Cactus
Cholla cacti are actually mostly branches. The ‘stems’ are instead modified, segmented branches built to hold water.
Something I only learned recently:
I’d thought cactus spines were meant only as protection against predators. Oh how wrong and narrow-minded I was.
For starters, they’re apparently highly specialized leaves, that grow out of a reduced branch. They mainly keep the plant cool and somewhat shaded – almost the opposite of a normal leaf, which grabs as much sun as it can. These spines also limit the amount of water loss, because they just don’t evaporate water like a big living leaf does. Photosynthesis is left to the body of the cactus.
The bristles on Cholla cacti (for most species) are actually wrapped in a thin paper sheathe with a light color, which helps further keep the heat off.
These plants start most often by clonal propagation. Like other cacti – a piece breaks off and falls onto the ground. After a while, it starts to produce roots. Eventually, a clone of the original plant starts growing. The segments of these plants are loosely held together, helping the plant fall apart cleanly. The various types of spikes and spines (including the barbed glochids) help the segments stick to animal skins and travel far across the desert.
The wood is considered a softwood. It’s faster growing than hardwoods, and lighter in weight than many others. The actual texture is pretty stringy, making the wood incredibly porous. The wood skeleton helps the cactus grow to greater height. As it stands (hah, good tall-plant pun), I’m not sure why it would want the greater height, but I will guess:
- Keeps the bulk of the plant (and its stored water) away from the heat of the desert floor
- Reduce the potential for rot if flooded with water during a rare rain
- Give the spiky and spiny segments the ability to detach and stick to creatures at all heights
The lightness of the skeleton is probably due to the shallowness of the cactus roots. If the skeleton were heavier, the roots would need to spread farther and deeper to anchor the plant against wind and its own weight. On top of that, this isn’t the same kind of wood as is seen in trees – nor are branches and leaves going to sprout from it in the same way.
It’s just weird wood, darnit.