One of the technical challenges that makes raising carnivorous plants so interesting is keeping them fed and hydrated. In this article we will explain why you need distilled water for your carnivorous plants.
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Carnivorous plants like Venus fly traps, pitcher plants, sundew plants, and cobra lilies need continuous moisture—and they are very fussy about its source. Tap water can kill them, and rainwater and distilled water are required for their survival.
In this article we will explain why carnivorous plants need the most mineral-free water possible, and how you can keep your carnivorous plant collection growing strong with the right water sources.
Carnivorous Plants Don’t Get Their Nutrients the Same Way As Other Plants
Related: Best Carnivorous Plants for Gnats
Carnivorous plants have the same nutritional needs as any other plant. Healthy carnivorous plant growth requires nitrogen, phosphorus, and potassium, just like any other plant. Carnivorous plants also need trace amounts of minerals. The way carnivorous plants get their nutrients, however, is very different from other plants.
Non-carnivorous plants get their nitrogen and phosphorus from the soil through their roots. (It is also to provide plants with nitrogen and phosphorus through foliar feeding with liquids like dilute fish emulsion and dilute Miracle Gro.) Carnivorous plants can get up to 100 percent of the nitrogen and phosphorus they need from the insects they trap and digest. However, when a carnivorous plant’s traps are empty, scientists have found, the plant actually leaks these nutrients back into the environment to feed the bacteria that help it digest the insects it traps.
Hard water has minerals that “pull” even more nitrogen and phosphorus out of a carnivorous when it is splashed on a carnivorous plant’s traps. Rainwater and distilled water don’t do this. The net effect of splashing a carnivorous plant with tap water is to pull nutrients out of the plant so that even if every trap has an insect, it will still starve.
Of all the minerals that can be dissolved in tap water, calcium does the most damage to carnivorous plants. If your tap water is the kind that clogs your water heater unless you have a water softener, then you must be very careful not to use tap water on your carnivorous plant collection. And you must avoid some common mistakes people make trying to use tap water on their insect-eating plants.
Alternatives to Using Distilled Water on Carnivorous Plants That Never Work
Beginning carnivorous plant gardeners often try shortcuts when they just don’t have time to buy the right kind of water for their plant collection. Certain methods of collecting water just won’t work, or even make the problem worse.
Boiling water and letting it cool overnight
Boiling tap water is a great way to get rid of bacterial contamination. But the problem with tap water for your Venus flytraps, pitcher plants, cobra lilies, and sundew plants isn’t microbial contamination. It’s minerals in the water.
Boiling water concentrates the minerals that damage your plants. Even after it has cooled down to room temperature, it causes more damage to carnivorous plants than water straight from the tap.
Letting water stand overnight in a bucket or a pan
Putting water in a pan or a bucket with the greatest surface area possible (that is, the thinnest layer of water possible) really isn’t a bad idea for refilling your aquarium. Tap water usually contains chlorine. Aerating tap water reduces the amount of chlorine and makes it healthier for fish.
However, this method also concentrates the minerals that cause damage to carnivorous plants. The result isn’t as toxic as water you have boiled, but it is still even more damaging to carnivorous plants that water straight from the tap.
Straining water through a coffee filter
Sorry, a paper filter isn’t fine enough to remove calcium, fluoride, magnesium, and other reactive contaminants from tap water.
Alternatives to Using Distilled Water on Carnivorous Plants That Sometimes Work
There are other methods of collecting water for your carnivorous plants that could work if you are very careful with them. Here are some methods that many serious beginners to keeping carnivorous plants have tried with varying degrees of success.
Collecting rainwater
Carnivorous plants in the wild depend on rainwater, so why not collect rainwater for taking care of them indoors? Rainwater collection, where local rules and regulations permit it, is a great conservation method and a terrific substitute for tap water. However, there can be some of the same problems with rainwater that there are with tap water, depending on your rainwater collection system.
Related: Best Carnivorous Plants for Indoors
If your location receives only sporadic rainfall, dust, dirt, insects, and bird droppings may accumulate in your collection system. Decaying organic matter releases nitrates and nitrites that are toxic to carnivorous plants.
If your location receives rain on a regular basis, and your collection system is connected to filters, and the rainwater isn’t rolling off asphalt shingles or a copper roof before it is collected, then rainwater can be a good source of water for your carnivorous plants. It can be just as beneficial as distilled water for your carnivorous plants.
Another acceptable approach is just to put out nonreactive (glass or ceramic) baking dishes or casseroles or even decorative pots out in heavy rain. Let them catch as much rainwater as they can, and store the rainwater in a glass (not plastic) container in the refrigerator until you need it. Or you can invest in a contaminant-free rainwater collection system.
Collecting condensation from cooling units
The steady drip of condensation from refrigerators and older central air conditioning units creates an ongoing cleanup chore, so why not catch condensation to water your plants? This method can work if the condensation does not fall from a copper coil.
Collecting water from a dehumidifier
Dehumidifiers remove more moisture from the air as liquid water than most carnivorous plant growers need to water their plants. It is important to make sure the water isn’t collected in a metal pan and isn’t contaminated while it is being collected.
Operating a solar still
Solar stills are a great way to make your own distilled water. You just need to place it in a location where it won’t be contaminated by dust, leaves, or animal activities.
Ways of Watering Your Carnivorous Plants That Will Always Work
One way of making water that will always be acceptable for your carnivorous plants is to buy your own reverse osmosis system. Reverse osmosis forces water through a semipermeable membrane to take minerals out and highly purified water flows through. These kinds of water purification systems are expensive and can be hard to maintain.
A simpler approach is just to buy distilled water, but not every kind of purified water at the market is really distilled water. Look for these two phrases on the label:
- “Purified by Distillation” or
- “Purified by Reverse Osmosis.
Statements about purification by UV light or carbon filters don’t count. “Drinking Water” is not the same as distilled water. Water you buy from a vending machine must also be labeled as purified by distillation or purified by reverse osmosis to be safe for your carnivorous plants.