freewomyn,

It may depend on where you live and what your source of water is, but I did this in Tempe for many years without any negative consequences.

Give it a try. If your plants start showing signs of excessive salt, then you could stop.

Good luck.

There are two things to consider when using water from an evaporative cooler.

1. If you use the water that flows over the pads and then exits the cooler you will probably not harm your plants, however, this could be very inefficient depending on how much extra water you are dealing with. Coolers typically use between 90 and 200 gallons of water per day.

2. If the water is recycled through your cooler with a pump and flows over the the pads more than once, accumulated salts in the water will be harmful to your plants. Some coolers have a float in a basin in the bottom that allows fresh water to fill the reservoir. Then the water is cycled to the top of the cooler pads over and over. The water that accumulates can be almost like brine and very salty.

Here's a link to more information.

Here is a link that might be useful: Evaporative Cooler Water Use

I've done this for years without any problems. The first cooler was one that might have been 30 years old. Now I've got a MasterCool with clean machine that dumbs every 8 hours. I see no difference. I just hooked up a soaker hose and forget it.

If I was watering plants that like acid soils - gardenias - I can imagine a problem.

We have a gizmo on our cooler (I can't think of what it is called) that dumps the water out every 6 hours and puts fresh water in. We use that water to give all of our plants a drink. After only 6 hours, I don't think the water has time to get too salty and we have the added benefit of never having that old fish tank smell in the house. Said "gizmo" can be found at Ace Hardware in their cooler parts section.