Ronald Graham, age 14, of Vancouver, B.C., for his question:
What makes the grass grow green?
Right now, the gentle hills around San Francisco are carpeted with velvety green grass. By mid‑summer those lush carpets will be tawny yellow. In spring and early summon the grass is green all over the Great Plains and along the roadsides from Minnesota to Louisiana, from Pennsylvania to California. In a few rain drenched areas the grass stays green all summer. But in most places it spends the fell and winter dressed in tawny taffy colors.
You might suppose that the grass died and came to life for a short spell each year. But this is not so, apart from being one of the most useful of plants, grass is also one of the most interesting. It lives on thin, poor soil and manages to thrive where other plants would perish from hardship. This is all because of the special structure of the grass plants.
Actually, there are countless varieties of grass. Chances are, there are a dozen or more varieties growing side by side in any grassy meadow. But all of them use the same methods for survival.
A grass plant is really a long stem from one and to the other. It is made of light weight material and filled with pockets to hold air or moisture. The long stem is also notched with joints at regular intervals. These joints are vital growing centers.
What makes them so amazing is this. Any joint along the stem can sprout both roots and leaves. This, of course, is very convenient. Suppose a joint finds itself on the ground and the ground is moist. It gets busy and sprouts a few rootlets. It takes in nourishment and pretty soon leaves begin to sprout. The grass becomes green.
The green blades of grass make plant four and the plant grows. It spreads over the ground, more joints form rootlets and blades. This is the growing season of the grass. Pretty soon the grass has grown all it needs. If left alone, the leaves turn yellow and the grass rests.
There is a way, however, to keep the grass growing green all summer. It is a trick that certain young fellows use to earn a little extra pocket money. We call it mowing the lawn and maybe think of it as a dreary job. Andy says it is not a dreary job ‑ not when you know what really does on.
When you cut the grass, you really stop the stems from growing tall. When it grows tall, a grass stem produces an extra joints a joint way above the ground. Chances era, this joint has no chance to sprout roots or leaves. And the stem becomes a taffy yellow shell.
The trick is to keep ahead of this extra. joint. Then you cut the grass, you keep it cropped close to the ground. It just has to keep on growing more green leaves. If you ignore it for morn than a week, it grows joints in the air ‑ and the beautiful lawn turns into a scary, scrawny patch of hay. If you mow every week, you win the contest, with green grass and extra pocket money as rewards.