There is just something about rain. Rather, there is something special about what a nice rain does for a garden. You water, you don’t water, you plead, you pray, you dance, it doesn’t matter. When it rains, the plants get happy. Every gardener knows this. I have had many conversations with many different people about this magical ability of rainwater to make plants thrive. And it has pretty much just always been chalked up to magic. No other explanation.
It’s not a new idea. Over 400 years ago, Saint Theresa of Avila described how prayer is like watering a garden. She described four different methods of watering a garden, and related each method to a different, deeper, level of prayer. For this piece, I’ll stick to what she said about watering. She wrote that you can take a bucket to the stream, get water in the bucket, and pour it on the plants. Or you can rig up a pulley system, or windlass, to get the water from the stream, and this is better and less work. Or you can divert the stream to the garden, which works really well, and is easier yet. But the best way to water a garden, she wrote, is rain.
So people have always noticed this. Then, this winter my wife and I went to Carlsbad Caverns National Park, and I finally learned why. The Guadalupe Mountains in extreme southeastern New Mexico are the remains of an ancient ocean reef. Ancient reefs are limestone. Near this ancient reef there are oil and gas deposits. The reef today is absolutely riddled with caves. The “Big Room,” 750 feet below the visitors center, is large enough to hold the U.S. Capitol Building twice. Really big, and unbelievably beautiful. Another cave, called the Lechuguilla Cave, is still being explored. So far they have discovered 135 miles of it, and they get a couple more miles every year. There are caves everywhere in these mountains. Something really weird happened to this old reef to make that happen.
The theory is that at one time the reef was saturated with salt water from the nearby oil and gas deposits. This salt water contained hydrogen sulfide. When the hydrogen sulfide combined with “oxygen laden rainwater from the surface,” sulfuric acid was created. This acid dissolved the limestone of the ancient reef, and formed all those caverns.
I read that sentence again. The one about “oxygen laden rainwater.” That’s it! When I tell people about watering their plants, I always tell them to not water too heavily because roots need oxygen just as much as they need water. Rainwater has both. It forms in the clouds, which are mostly air. Raindrops are full of air. Air is about a fifth oxygen, which makes roots happy. Most of the rest of it is nitrogen, which makes plants green. And I had to go 750 feet under the ground to figure that out. Maybe it’s not magic. Maybe.
Ken Williams Horticulturist