When it’s time to water our houseplants, most of us automatically head over to the kitchen sink and fill our watering can out of habit. While most tap water is perfectly safe for plants, it often contains minerals and chemicals that can build up in the soil over time. So, what would happen if we used more natural sources, like rainwater, to water our houseplants?
Is rainwater good for indoor plants? Yes! Because rainwater is naturally soft, meaning it is free of many salts, minerals, and chemicals, it is a very gentle way to water houseplants without causing build-up on leaves and in the soil. Rainwater is also slightly acidic, which helps to balance out the soil’s pH, which typically gets watered with more alkaline tap water.
This may not be all that surprising. After all, rainfall manages to keep all of our natural outdoor ecosystems thriving around the world. However, even though it’s a pretty basic concept, we tend to lose touch with the fact that our houseplants are just outdoor plants we’ve moved inside. They are going to respond just fine, if not better, to being watered with rainwater.
Why Is Rainwater Good for Houseplants?
There’s a whole lot of stories out there from people who swear by rainwater. Many folks report that switching to watering their houseplants with rainwater caused immediate improvements in the overall health, look, and vibrancy of their plants.
However, what are the specific benefits of rainwater, and how exactly can it improve your houseplants?
Rainwater is Soft
The most significant benefit of watering with rainwater is that it is naturally soft. This means that there are very few salts, minerals, or chemicals in the water compared to what comes out of a tap hooked up to a municipal water line or well.
This benefits the plant because, each time you water, you are providing the moisture the plant needs without any additives that tend to build up in the soil over time. Additionally, this clean water is helping to flush out any excess salts and chemicals, which brings the soil back to a healthier state.
Manually softened water tends to have excessively high salt levels, mainly due to the use of salt to remove calcium and magnesium from it. As salt levels build up in the soil, it can disrupt the roots’ ability to properly absorb water and nutrients effectively. City water often contains chemicals like fluoride. Again, over time, these chemicals can build up in the soil and have adverse effects on the plant’s health.
The use of rainwater to water your plants will help mitigate these build-ups in the soil, and over time, prevent them from happening again, keeping your plant much healthier in the long run. Using water free of these chemicals and salts will also prevent build-up and water spots on your plant’s leaves.
Rainwater is Slightly Acidic
Depending on where you live, natural rainwater tends to have a pH of between 5.4 and 7.0. While most plants can tolerate a range of pH, most of them tend to be living in soil that skews more basic (or alkaline) than what is ideal. This is because tap water runs basic, usually around 7.5-8.0, to protect metal city water pipes from corrosion.
By using more acidic rainwater to water your houseplants, you can begin to lower the pH of the soil over time to a level that is more preferable to the plant. Many plants like a slightly acidic environment to really thrive, between 5.5-6.5, so keeping it at or below 7.0 can set your plant up for long-term success.
Rainwater Contains Nitrates
Around three-quarters of the atmosphere is composed of nitrogen, a compound essential to plant growth and function; however, most of it is in a very stable form of gas that is not easily accessible for plant life.
But there are other forms of nitrogen floating around in the atmosphere, called nitrates, that can easily mix with water. These nitrate particles can get absorbed by falling rain droplets and be deposited into the soil, where plants can easily utilize them, as they are already in the most readily available form for root systems to absorb them.
If you think about fertilizers, nitrogen is one of the big three macronutrients responsible for plant growth, typically being utilized for leafy stem growth and keeping plants nice and green. There are many stories about how people switched to watering with rainwater and seeing an immediate improvement to their houseplant’s color. I suspect this, as well as balancing the soil chemistry and flushing out chemical build-ups, all contribute to a plant’s greener appearance.
How to Collect and Store Rainwater
If you are interested in watering your houseplants with rainwater, the first thing you’re going to need is…well, rainwater.
There are a few different ways to collect rainwater, ranging from very basic to very high-tech (you can seriously nerd out on this topic). I won’t cover huge commercial or residential setups in this article, but they are easy to research if you think you want to commit to running your entire household on collected rainwater.
Lay Out Collection Containers
The first and most low-tech option is to put out containers or buckets in your yard and wait for the rain to come. While this is an easy option for most people, it tends to take up quite a bit of real estate in the yard, and you have to schlep a lot of containers back and forth to the house. Still, it’s a pretty low-cost way to start rainwater collection and see if you can witness any of the benefits of watering your houseplants with what you’ve managed to collect.
Use only clean containers without any chemical or oily residues. You definitely don’t want to go through the work of collecting water if you’re using old containers that used to contain herbicides, for example.
If you want to be extra careful, pick plastics considered “food safe,” which means they won’t easily leech any residues or chemicals into the water. Choose plastic containers that are made of type 1, 2, 4, and 5 plastics. Both Lowe’s and Home Depot sell “food grade” HDPE 5 gallon buckets that would work well for this task.
Rain barrels are a very common design for rainwater collection, typically because they are a manageable size and easy to hook up to gutter downspouts, allowing collection to occur from runoff on your roof.
I’ve seen a wide array of containers used for rain barrels, including old wooden wine kegs to new food-grade plastic 50-gallon drums. Most of these barrels have an opening at the top of the barrel to funnel water into and a spigot or hose bib near the bottom where you can let water out of the barrel. Many also have an overflow that you can attach a hose or pipe to in order to divert excess water away from your home.
One of my favorite cheaper options for a stand-alone barrel is this one on Amazon. This is the perfect size for a patio or deck, has a flat back for close placement against the house, and has an optional stand you can place it on for easier access to the hose bib. Installation is minimal, and you just need to direct a downspout to empty over the collection screen on top of the barrel.
Another option is this barrel. This works similar to the one above but has a built-in diverter kit you install into your downspout to reduce overflow situations.
Rain Barrel Arrays
If you’re looking for a way to collect more than 50 gallons of rainwater at a time, you can usually set up multiple rain barrels in a staggered array, where water from a downspout is diverted to one barrel, and then subsequent barrels are placed as lower positions for the overflow to drain into.
These are typically used for more than just watering houseplants and tend to be DIY setups using plastic drums and PVC tubing to create a setup that works in a specific space.
For those of you who reside in colder climates and find yourself in a blizzard, snowmelt is just as good as rainwater.
Just fill up any large container or bucket with snow, bring it inside, and let it melt and rise to room temperature. Try to only collect fresh snow without dirt or debris and stay away from roadsides where the snow may have been plowed from salted roads.
Watering Your Plants with Collected Rainwater
If you’ve collected rainwater in containers or a rain barrel, feel free to use it as you need it. Water your houseplants as you normally would, but rather than reaching for the tap, use what you already have on hand.
If you use containers laid out in the yard to collect rainwater, try to consolidate what you’ve collected into a larger, deep bucket, preferably with a lid. This will make it easier to dip a watering can in to fill, and the lid will keep the water fresh and clean in between plant waterings.
If you purchased a rain barrel, you can take your watering can out and fill it with the spigot near the bottom of the barrel. Typically, water stored in rain barrels stays clean for quite a while, but you may want to flush it out every so often to ensure your plants are getting the freshest water.
Over time, monitor your plants, paying special attention to their growth, color, and soil. Hopefully, within a matter of weeks, you’ll start seeing improvements to the plant’s overall health and appearance as the benefits of clean rainwater start taking effect.
Can Rainwater Harm Houseplants?
Generally, the answer to this question is no. Rainwater is typically considered a naturally clean source of water for all living things, so there aren’t a whole lot of cases where rainwater would be detrimental to your houseplants.
If you live in a very industrial area, there may be byproducts of industrial production that can get captured in raindrops and eventually watered into your plants, however, the risk of this is generally very low in most places.
If you’re collecting rainwater in barrels from your gutter system, there is a chance that it can contain chemical runoff from the roofing products used on your home, but again, this is likely just fine for your plants and not anything to be concerned about.
One potential threat, which isn’t exclusive to just rainwater, is water temperature. If you are using a rain barrel, just remember that the water you collect will be subject to the temperatures outside, and over time, it can get very cold or very warm, depending on the weather.
Just be mindful of this so you aren’t subjecting your houseplants to extremely hot or cold water, which can wreak havoc on the delicate root systems. If you find your rainwater is really hot or cold, allow it to sit inside until it reaches room temperature before applying it to your plants.
Overall, collecting rainwater to use on your houseplants is a great idea. Not only is it an eco-conscious and cheap way of conserving water, but your plants will benefit from its purity, as it helps restore balance to the soil, properly aligns pH levels, and provides essential nutrients for easy utilization by your houseplants.
There are many ways to collect rainwater, but you should get creative with your setup to utilize the space around your home efficiently and to make it easy to use. Once you’ve got a system that works for you, you can bask in the glory of all your happy houseplants. Best of luck!