If you're a gardener, you've probably noticed that your plants seem to look healthier after a good rain than they do after you irrigate with tap water. In fact, young plants often have a growth spurt after it rains. Rainwater is actually better for them than tap water, primarily because the latter has been treated with chemicals to make it safe for human consumption, and doesn't contain the same beneficial elements as rain. Perhaps it's time to consider a rainwater collection system to satisfy your watering needs while giving your plants what they like. In some states, you may even be eligible for incentives for collecting and using rainwater. Your water bill might go down as well.
What makes rainwater better
Chemicals in tap water can include chlorine and fluoride. Both of these can harm plants. Plants with long, narrow leaves are especially susceptible to damage caused by fluoride. Chlorine can be particularly harmful to indoor plants because it will accumulate in their containers.
Rainfall evenly distributes water across your outdoor garden over time. Giving your plants a quick watering with a hose or sprinkler may apply too much water too quickly in some areas while not supplying enough water in others. Too much watering too quickly just causes the water to run off rather than penetrate. A good, slow rain allows time for the water to penetrate deeper into the ground and beneath the plants' root systems, carrying with it salt accumulations that stunt growth and other chemicals that may have harmed your plants. That's why, after a nice rain, plants have growth spurts and appear healthier.
Over-watering with tap water can cause root rot by depriving the roots of oxygen. Rainwater, however, has a high oxygen content. So, even if you get a lot of rain and the soil is highly saturated, you will not need to worry about root rot due to rainfall.
Rainwater releases essential nutrients into the soil that plants must have in order to grow and be healthy. Nitrogen is one of those nutrients and is necessary to facilitate photosynthesis, the process plants use to create oxygen using carbon dioxide, water, and sunlight. Nitrogen is also required for healthy green foliage. During storms, lightning causes nitrogen to combine with oxygen and rainwater, thereby effectively fertilizing your garden.
Other essential nutrients also end up in the soil thanks to rainwater. Rain is slightly acidic, and plants like a little acid in the soil. The acidity of rainwater also causes iron, manganese, and copper, all essential to plant health, to be released into the soil as well.
Given the beneficial qualities of rainwater, you may wish to install a collection system. Granted, using collected rainwater will not prevent uneven distribution during irrigation, but it will allow you to take advantage of the other benefits. Your water bill may also go down and, depending on where you live, your state might even provide some incentives for you to collect and use rainwater. To see what regulations apply in your state and whether any incentives are offered, visit the Department of Energy's site at energy.gov/eere/femp/rainwater-harvesting-regulations-map.
Rainwater collection systems are simple, especially if you already have gutters and downspouts you could use to feed one. You can build your own with a rain barrel, faucet, and hose or buy one ready-made. They're available to order online or to buy at local garden supply centers. Prices for most kits range from about $60 to nearly $200, primarily depending on the size and composition of the barrel.
A good, slow rain evenly irrigates your garden, washing away salts and other chemicals while adding essential nutrients your plants need to survive and thrive. Capturing rainfall to use when your garden needs it rather than using chemically-treated tap water will allow you to take advantage of its qualities even during dry weather and to use it on your indoor plants as well. You may even save money over time and be rewarded with other incentives for installing a collection system. They're inexpensive to buy or, if you're the do-it-yourself type, you can build your own with only a few components.