Hello lindaflower,

Venus Flytrap leaves turn black when they die from fertilizer. In bright sun, they turn red if the cultivar is not an all green type like the Dente. If your Venus Flytraps are not in intense enough light, they will not produce red coloration no matter what cultivar they are.

It usually takes a few weeks or even months to observe the evil work of impurities in carnivorous plant media as it usually builds up slowly. Just a tiny bit can be introduced over time each time you water the plant, then poof, dead plant. Each roof is going to be different, so if dead matter builds up on your roof from leaves, bird droppings, etc, then washes off in the water, it might affect the plants. If the roof materials are toxic to carnivorous plants, like copper nails and runoff catch systems, then toxic copper impurities are being slowly introduced. Some roofs might be clean and runoff might be safe to use from them. The thing is, who knows what might be the culprit, so just keep changing your tactics until you figure out what killed the plants before.

I found out the hard way that keeping a supply of rain water in a 55 gallon drum was a bad idea as it eventually builds up microorganisms and nitrogen levels go up over the course of weeks or months. You might be fertilizing the plants without realizing it. I always use distilled or reverse osmosis water that states that all impurities have been removed and nothing added.

Bingo! Thanks mutant. They started declining gradually and my sundews are looking bad too. There is a lot of organic matter (decayed leaves)in the gutters and the water in the rain barrel has been standing for quite some time.

I'm going to drown my remaining plants in distilled water and hope it's not too late.

Okay, here's another question: can I use the water that drips from the air conditioner condenser? It's basically distilled since it has come from the water in the air and shouldn't have any minerals or salts in it. If it is too acidic will it hurt my plants? I know that they are already living in acidic media... but a little too much may be all it takes.

Anybody know if that will work?

Supposedly, AC water is safe.

Most folks I know who use "rain barrels" do not collect the runoff untill after it has been raining hard for at least 15 minutes (10 if you're impatient). This allows the hard rain a chance to "wash" the dead bugs, leaves etc out of the gutters before collection and rinses off the roof itself. They then make sure the barrells are kept shut against leaves, etc falling into them and use the water within two to three weeks.

I've used dehumidifier (DH) water for years. It works great.

I don't trust rain water where I live. I live in a farm community and dust from the fields builds up in my rain barrels. Where there's "field dust" there's fertilizer, herbicides, and pesticides. It's just safer to use my DH water.

Water from the AC unit would basically be distilled water from condensation, so as long as the AC unit does not have any copper drains or parts, it should be safe.