Saguaro by the Numbers. Maybe

David SchwartzI’m going to install a little window in my mind so you can see how it works. At least how it is working at this moment. It may not work in quite the same way at any future time. Here’s my promise: other than having decided on the overall idea, I have not planned the specifics of what I’m about to write. Instead, I will record my thought processes (if there are any) as they occur, to see if something interesting, useful or otherwise worthwhile happens. And if not, you’ll get to see that, too. Ready?

Here’s the context. It happened earlier this month. I was in Phoenix for school visits, and I had a free afternoon so I went to the Desert Botanical Garden. Great place! I was looking at an exhibit on saguaro cacti, the Sonoran Desert’s quintessential plant. A mental image of this charismatic cactus with upcurving arms may be the first association many people have with the word “desert,” although saguaros grow only in this relatively small desert of southern Arizona, northwestern Mexico and a sliver of southeastern California. I knew these are very cool plants from a very hot place, but of course I was eager to know more.

So I read the interpretive signs and I was bowled over… with numbers. That is to say, numerical facts about saguaros. Being a numbers guy and a math author, the hairs on the back of my neck stuck up like cactus thorns. Here are a few of those numbers:

two — a single saguaro plant releases up to 40 million seeds in its lifetime

 — saguraros grow incredibly slowly: about ½ inch in the first year and one foot in the first 15 years. Then they start cruising: in 40 or 50 years, they may reach ten feet and it is not until they are 50-100 years old that they begin to sprout arm buds. Some live up to 300. Their maximum height is 40-60 feet. When a cactus poacher (oh yes, they do exist) digs up a six-foot saguaro to plant in front of his house, a replacement in the wild will take about 30 years reach the size of the poached plant (which will probably die).

— one mature saguaro can store 1,500 gallons of water (that’s 6 tons) in its spongy pulp  — enough to last several months. It can lose 2/3 of its stored water and survive.

There were many other numbers but that’s enough for now.

So here’s what happened. I thought to myself, “Hey, how about a book about saguaros and their numbers?” Saguro Numbers or Saguaros by the Numbers or Number the Saguaros or something like that. Or maybe not like that. But let’s not get hung up on the title. The thought did not evade me that if I could pull it off, sequel possibilities would be countless:  Elephants by the Numbers, Great White Sharks, Dinosaurs … even Oceans, Earth, The Solar System, etc.

So what about it? Having an idea for a book (or a series) is the easy part. Figuring out a way to execute the idea is another matter. It’s kind of like the business plan for a book. Without it, all you’ve got is something to talk about at cocktail parties. With it, you’re in business. Maybe. So what should I do with this inchoate idea of saguaros and numbers? Let’s see…

First thought out of the gate: like Harper’s Index. You know, “Rank of Portland, Oregon, of all cities in per capita consumption of Grape-Nuts: 1” or “Number of incidents worldwide last Christmas (2005) of ‘Santanarchy,’ which involves roving mobs of unruly Santas: 29”

So, instead we could have, “Number of seeds a saguaro cactus produces in its lifetime: 40,000,000.”

OK. Possible. But a bit dry, and it seems a bit too much like, well, Harper’s Index. A derivative work. Heaven forbid. And it might get tedious. But with additional text to explain and fill out the saguaro’s story, it could work.


So, maybe this instead: I’ll build the book around a number line. One gargantuan number line could extend across all the pages. Number lines are an important way for children to understand number concepts, and along the number line I could mark numbers of importance in understanding saguaros. At the number 10, there could be an arrow or an indicator that you can follow to an explanation that in 10 years, if all goes well, the saguaro will reach a height of one foot. (I suppose I could just as well put the marker at the number 1 and say that one foot is the height of the saguaro after ten years.) At 1,500, you’d have the number of gallons of water a plant can store. (Or it could be 6 for 6 tons.) And at 40,000,000 the number of seeds produced in a lifetime. Of course there would be many opportunities to add supplemental information to fill out the picture. (Let me not discuss right now the question of whether to use metric units of American units or both. We’ll save that for another day. We’re just brainstormin’ here.)

OK, but a few problems with my number line idea come to mind. For one, how can I set up a number line on a scale that shows 1 and 6 as well as 1,500 and 40,000,000 and plenty of points in between? I guess there are ways. I could leave out sections (showing jagged lines to indicate discontinuities). Yeah, that’s possible. Or how about this: multiple number lines on different scales. One for growth. That would work. Another for production of things like seeds. Forty million. But what else could go on that number line? Maybe nothing else. Does it make sense to create a number line with only one point on it? Maybe not.

But wait a minute, suppose I created a bunch of number lines, on different scales, and I showed not only the saguaro-relevant numbers (example: 1,500 gallons of water stored) but other values that could put it into perspective, such as how much water is found in a large watermelon, in the body of a human, in an Olympic-size swimming pool.

That could work. But let’s think about it. Do I really want a book of number lines to tell the story of a saguaro cactus? Maybe. Maybe not.

How about a book of math problems related to saguaros? “It has rained for 30 hours in the Sonoran Desert. A 40-foot saguaro’s roots spread 40 feet in all directions, and in the area above the roots, 100 gallons of water fall each hour. The saguaro can absorb half of that water. How much water can this giant cactus absorbed?” (Do you need the Teachers Edition? The answer is 1,500 gallons.) Then some narrative can explain that these plants really do this, how amazing they are, etc., etc. Nah, too much like a math textbook.

OK, how about a book with chapters that are numbered in an odd way. Instead of Chapters 1, 2, 3, etc., we can number the chapters according to the number being discussed. So it could start with Chapter 1 in which we feature the number 1. All the things about saguaros that come in ones. Or just one thing: in one year it grows half an inch. But then we might skip to chapter 10. That’s how many years it takes for the saguaro to grow to a height of one foot. And I would talk about water absorption in Chapter 1,500.  Chapter 40,000,000 is for the seeds. (Hey, I could start with Chapter ½ because it grows half an inch in the first year.)

Hmmm. Not bad. Original (I think). Maybe I could pull it off. Maybe not. That’s all I’m coming up with right now: lots of maybes and maybe nots.

And maybe, since the great horned owl of my bird clock just hooted (as the clock’s little hand reached the number 12), I’ll sleep on it. Tomorrow is another day for a few more maybes. And then maybe I’ll start writing to see which of these maybes I like best. Or maybe I’ll think of a better one. (In the meantime, feel free to vote for your favorite or suggest your own maybe.)