My sister looking for the top of a tall tree in Malaysia.
High school biology first taught me the meaning of xylem. If you flip to the x section of an old-fashioned dictionary, you’ll see it’s one of the few words in English that start with the letter x. That puts it into a rarefied elite.
Xylem, for those who don’t know or don’t remember, is part of the anatomy of a vascular plant. Don’t panic. I’m not about to bore you with a science lesson. All you need to know is xylem is the part of a plant that speeds water and minerals from the roots to the leaves. Of course, speed is a relative term here. We’re talking about plants, which are not in a league with sprinting cheetahs or falcons in their power dives. Sap flow rates are measured in centimetres per hour (inches per hour).
When you think about it superficially, plants have a Zen-like existence. All things happen at a measured pace. Peaceful. Relaxed.
Peaceful? Yeah, right. So they would have you believe. Tell that to the raspberry cane being smothered by a morning glory vine or a sprig of clover struggling for sustenance after the “me first” nutrient plundering of a eucalyptus tree.
It’s interspecies war. Roots duel for supremacy in the realm of water and minerals and the above-ground parts of the plant strive to overreach or crowd out their neighbours. By growing faster than the other plant or climbing up the other plant, they vie for sunlight.
Dealing with a plant’s need for territory and resources is the heart of gardening. Have you ever ignored the spacing directions on a packet of seeds? You know, the part where they say something like, “Space seeds 4 inches apart and thin to 8 inches.” These aren’t frivolous numbers, as I discovered years ago when I actually paid attention to how much room I was giving my onion sets. My onions had been a nice size. The next year, when conditions were good, I gave them more room, and their size zoomed to magnificent. The right amount of space maximizes yield. You don’t get more by planting too close together.
China discovered the wisdom of experienced farmers versus the power wielded by politicians back in the Great Leap Forward. Consider the instance when rice plants, by order, were crowded so close together fans had to be used to circulate air and try to keep them from rotting. Not even the fans could help give each plant the amount of sunlight it needed. Those few plants that didn’t die due to the crowding produced poorly.
I am frequently amazed to see how closely someone has planted a line of trees. And what are people thinking when they plant a tree sapling, a Douglas fir, for example, within two metres of a building? Forget the word “sapling” people, this is a TREE.
And yet, people will buy a tiger cub as a pet because it’s cute. Yes, at ten pounds, it’s definitely cute. An adult tiger? That can be 400 pounds of muscle, claw, and fang.
Wait. Tiger? Hold on. What was I talking about?
Oh, yeah, crowding…plants…xylem.
Xylem is no big mystery to science. It was first described and named in the 17th century, and everybody knows how it works. Right?
Yes and no. Consider that a person could draw water up a straw that was 10 meters (about 30 feet) long, but no longer. That’s the max. Then consider a redwood tree drawing water to its growing top some hundred metres (over 300 feet) in the air. Try asking a botanist how a redwood gets water from its roots to its top, then brace yourself for a lot of fancy verbal footwork. Here’s a quote from Wikipedia:
“Over the past century, there has been a great deal of research regarding the mechanism of xylem sap transport; today, most plant scientists continue to agree that the cohesion-tension theory best explains this process, but multiforce theories that hypothesize several alternative mechanisms have been suggested, including longitudinal cellular and xylem osmotic pressure gradients, axial potential gradients in the vessels, and gel- and gas-bubble-supported interfacial gradients.”
Oops, I said I wasn’t going to hit you with a science lesson and then I did. My bad. Clearly, I need to wrap this up. Xylem is the x word in my alphabet of gardening, and however the plants we grow and the xylem within them get water from their roots to their leaves, I admire their bioengineering expertise.
It doesn’t matter how they do it, they do it. Like they say, “the proof of the pudding is in the eating.” Or, in the case of my garden, it’s the proof of the broccoli, the chard, the zucchini, the corn, the apples, the rhubarb…
Please share my letter-learning video with anyone you know who is just learning to read. This one features the letter X.