In a perfect world, rain would provide the perfect amount of water required to help our tomato plants thrive. However, weather in the gardening season is seldom perfect. (OK, never perfect.) So we often have to supplement that unpredictable rain with water from the garden hose to keep those tomatoes happy. But what if my garden hose is tied into my water softener? Is softened water OK for tomato plants?
Spoiler alert: No. I unknowingly was watering my whole garden with SOFTENED water for 15 years before discovering my goof. Year after year, the health of my garden, especially my tomatoes, would ebb and flow based on how much and how often it would rain. During dry spells, I’d manually water my garden with the regular ‘ol tap in my backyard. What I didn’t realize was that I was slowly killing my plants each year! I’m on the path to rectifying this error, but hopefully this information can provide some guidance to others!
What exactly is Softened Water?
Softened water is presumably hard water run through a water softener. (Brilliant, thanks for the explanation!) Hard water is water from the city source that may contain high levels of certain minerals (primarily calcium and magnesium.) The process of water softening essentially strips out that excess calcium and magnesium.
There are primarily 2 types of water softeners:
- Salt-based
- Non salt-based
The most common type of water softener is a salt-based system. It’s the type I have in my home. In salt-based softeners, the hard minerals are essentially replaced with sodium (salt.) The process is a bit mysterious, but the hard water enters through a main water pipe and (sometimes) directly into the softener. Resin beads grab on to the calcium and magnesium… and you know what? That’s not the important part. This article is NOT about how a water softener works. You should just know that a water softener removes hard minerals and replaces them with sodium.
Here’s a decent explanation of how a salt-based water softener works:
https://www.scientificamerican.com/article/how-do-water-softeners-wo/
Why should you have a water softener?
Hard water isn’t necessarily bad, per se. But those hard minerals (again, Calcium and Magnesium) can leave crusty deposits on fixtures and wreak havoc on water appliances. Those minerals can also mess with the effectiveness of soaps and detergents. This can lead to a need for increased soap to get the job done effectively.
Hard water = more soap.
Hard water = more crusty deposits on fixtures.
Some areas of the country have more “hard” water than others. I live in eastern South Dakota – where the concentration of calcium carbonate is between 181-250 milligrams per Liter.
You’re probably thinking: Woah, that’s a lot of calcium carbonate milligrams per Liter! (That’s weird if you were actually thinking that.) Yep, my incoming water is pretty hard, so it makes sense for me and many others to treat our water through the magic of water softeners.
Here’s a cool map of typical water hardness levels across the country. If you live in Maine, you probably don’t need a water softener. If you live in South Dakota, you might want one.
https://www.usgs.gov/media/images/map-water-hardness-united-states
Is rain considered hard water or soft water?
Rain is “soft” by nature. Rain doesn’t contain high levels of calcium or magnesium. Those hard minerals are picked up after rain water comes in contact with the ground and picks up the minerals on the eventual way to our homes.
So then is rain the same as water from my water softener?
Not exactly. Both have low levels of calcium and magnesium, but treated (softened) water ADDS sodium to the mix! And guess what, that sodium wreaks havoc on tomato plants! Excess sodium in the water causes soil imbalances. Too much sodium in the soil actually messes with the water transportation to the fruit. It tricks the plant into thinking it has taken up more water than it actually has. And too much of this can essentially cause the plant to die of thirst! Pleasant, right?
What happens to tomatoes if they are watered with softened water?
Occasional watering with softened water likely won’t do much damage to tomato plants. But if you are exclusively watering with softened water, the tomato plants won’t uptake enough water. And that lack of water uptake will mean a lack of nutrients to the fruit. And you will likely end up with dreaded…blossom end rot!
What is blossom end rot?
Blossom end rot is a condition where the blossom of the tomato (bottom of the fruit, opposite of the stem) breaks down and rots. Other plants like peppers and squash can suffer from this condition too.
What causes blossom end rot?
If you search for causes of blossom end rot, you’ll find 2 consistent themes:
- Inconsistent watering
- Lack of calcium
Sound familiar? That sodium is causing the plant to think it has enough water. So it doesn’t drink as much as it should. And if it isn’t drinking enough water, it isn’t going to carry necessary nutrients to where they need to go. You know, nutrients like CALCIUM! That same calcium that was stripped out of the delicious hard water after running through the water softener.
Should I avoid watering tomatoes with softened water?
I get it. Your tomatoes are thirsty. It hasn’t rained in days. They are parched and they need some water! But try to avoid watering your tomatoes with softened water if you can. Softened water removes calcium (which tomatoes need) and adds sodium (which tomatoes don’t like!)
If you are watering your tomato plants exclusively (or at least often) with softened water, you will likely see unhealthy plants. They might survive, but they will likely not thrive. The fruits that do form might develop that nasty blossom end rot.
Maybe a shot of softened water here and there won’t hurt. But try to find alternatives:
- Use a spigot that bypasses the water softener. I’m guessing if you have the problem with softened water outside, you likely don’t have this option. But check your outside taps!
- Temporarily bypass your water softener. Most softeners should have a manual bypass. Mine does! Turn the bypass on. Make sure you run ample water through the hose (it was likely partially filled with that softened water :).
- Use rain water. Duh, just make it rain, right? I mean use a rain barrel. If you aren’t capturing rainwater yet, you should really do that.
Summary:
Don’t water your tomatoes with softened water. I unknowingly did it for years. And I had years of failed tomatoes! (Yes, that says something about my stubbornness and/or intelligence that I kept trying after all the failures.)
Occasional watering with soft water is likely going to be fine. But find an alternative. It’s going to get dry. Those tomatoes are going to need something beyond sporadic rain. Capture rainwater or figure out how to bypass your water softener. Or do both!