You might think the answer to this is obvious: the plants get a nice long drink! But what about rainwater is so desirable to us garden buffs? There is more than meets the eye to these beautiful little raindrops we Californians run from so adamantly.
Its all in the nutrients! Rain drops have the ability to gather nutrients to them throughout the entire process of the water cycle. These nutrients, including one that plants need in large amounts, Nitrogen, are gathered as the water evaporates and moves through the atmosphere to its dreamy destination. They are also washed away from through concrete and other hard structures, like our cars, rinsing away dirt and decay from them while also gathering nutrients that flow into the soil and water systems.
But why exactly do we care about the nutrients gathered in the rain? Just as human beings are encouraged to take a multivitamin by many reputable sources, plants need certain nutrients to keep their structures healthy and their functioning in tip top shape. Nitrogen is a major part of Chlorophyll, the pigment that allows plants to capture the sun and produce sugars for their sustenance. It is also a major building block of amino acids, which make the proteins that keep our plants standing tall and strong. Along with Nitrogen, some other vital nutrients plants absorb are Potassium, Phosphorus, and even Calcium. Coming soon will be some videos on how to make elixirs of these nutrients from regular old household waste!
Nitrogen is a tricky one to get because it is abundant in the atmosphere in its gas form, two nitrogen atoms bonded in a tough triple bond, but requires a very energetic process to break its bond and become accessible forms for plants to uptake. There are two notable ways for this to happen: one is a lightning bolt hitting the gas, and another is being broken by beneficial bacteria found in healthy soil and the roots of certain plants. So, when rain has the ability to capture this golden resource gardeners will gladly receive it!
Another reason rainwater is like liquid gold to gardeners is that it is soft water. This means that it is free from the salts, minerals, treatment chemicals, and pharmaceuticals that are found in public water, groundwater, and surface water. That makes it ultra hydrating to the plants without the extras that can impart nasty chemicals. This may not be a big issue to your ornamental landscape, but it becomes an issue when we talk about a vegetable garden feeding your family.
Next, rainwater is slightly acidic naturally. Many plant species prefer their soil at a pH of 5.5-6.5, which is more acidic than a pH of 7 which is considered neutral. Treated water is often processed to be alkaline or basic, which means it is at a pH of over 8 often. This is because acidic water can wear down the pipes coming out of a water treatment facility over time. Greywater from your household--water you would collect from showering, washing dishes, etc--is often extremely basic by the time it has collected the soaps and other chemicals we use to clean and sanitize our bodies and homes.
Finally, rainwater often washes organic matter like decaying leaves and other plant matter into the soil where it helps retain water and feed the beneficial bacteria at the root of the plant. According to the Natural Resources Defense Council, each 1% increase in organic matter allows the soil to hold 20,000 gallons of water more! This is partly why the soil from monoculture plots (agricultural fields with one crop planted for acres and acres) is so unproductive, producing flavorless produce. Each season, farmers remove the entire plant, root system and all, and till the soil, exposing the topsoil to erosion. There are so many other issues with this system...but I digress.
So with that, any way you can collect rainwater for your plants is a great opportunity, and this goes for a few buckets to throw on your indoor plants as well. Rainwater collection systems are really fun to create and can really boost your family's resiliency when the impending drought worsens in our very dry California. Many arid regions around the world, including Cape Town, South Africa, are having to ration water to their citizens who scramble to grab it up with old milk containers and jars. Water is such a valuable limited resource we take for granted.
Interested in learning more or having your own collection system installed? Feel free to reach out!