My Grandpop-pop, Earl Poplin, is a real green thumb. He can put a stick in the ground and it will grow for him. He always says, “Rain is magic.” My dad, another excellent gardener, says this too. And if you follow this saying back far enough, I am sure all the old timers that ever gardened have said the same. As time has passed, and with a little more understanding of gardening and botany, I’ve come to appreciate the depth of wisdom in that simple statement. Many garden enthusiasts, including myself, share the sentiment that rainwater is the ultimate nourishment for plants, and that it is superior to tap water. But is that really true?
It is true! It turns out that rainwater contains natural nitrogen content. While tap water contains some nitrogen too, rainwater specifically contains nitrate. Here’s how that works; storms, and especially lightning in a rainstorm, facilitates a reaction between the nitrogen and oxygen in the air which produces nitrate. This naturally occurring nitrate is a goldmine for plants, nourishing them as it seeps into the soil. This phenomenon is called nitrogen fixation and gives rainwater a leg up over your regular tap water.
However, tap water is not necessarily bad for plants. I water plenty of gardens with tap water and they do just fine. Tap water is designed for human consumption, containing additives like chlorine for disinfection, fluoride for dental health, and sometimes sodium to soften it. Depending on who you talk to, saying tap water is healthy for people can be controversial, so we will steer clear of that landmine for now and say that we need tap water for civilization and our supply is meant for humans, animals, and plants alike. But while these additives may benefit us, they can cause some problems for our little green plant buddies. Over time, watering with tap water can lead to a buildup of salts and other minerals in the soil, potentially inhibiting plant growth. In more severe cases, the soil may need to be treated or even replaced, especially for potted plants. I can safely say I have never had that happen, but it’s something to keep in mind with water that has a high mineral content.
But why do my plants look so much better after the rain? Plants crave nitrogen-rich soil, and it makes their leaves greener too. This essential element contributes to their overall health and vitality. Farmers, being part-time chemists by necessity, have become adept at understanding the mineral needs of their crops, balancing between natural sources of nourishment like rain and artificial ones like fertilizers. But beyond the science and the chemistry, there’s something mystical about watching plants come alive after a good rainfall. A good long rain also tends to soak the ground fully, so the roots get more water than they would in drier conditions. One thing’s for sure, Grandpop-pop was onto something. Rain truly is magic.
If you want to learn more, feel free to swing by The Gathering Garden in Mount Gilead at the corner of W Allenton St and School St, if you want to discuss gardening with us, you can find out more about or workdays on our facebook page.
In these weekly columns, I will share the science of gardening and so many more interesting tidbits. Check back here every week for tailored Montgomery County garden advice, sharing our garden updates, and more.
Let’s grow together!
This article was originally published in the Montgomery Herald and is reused here with permission by Mary Poplin.