PHOTO: Jean L./Flickr
Lynsey Grosfield
April 15, 2016

Copper tools, sculptures and tape—here are a lot of garden products that use this malleable elemental metal. So what does all of it actually do for a garden?

Often heralded as a sort of natural or passive slug and snail repellent, copper in the form of tape on pots and rings around plants are purported to chemically and electrically deter gastropods from munching on plants. However, Robert Pavlis, who curates the blog “Garden Myths,” says the effectiveness of these tools is overstated. It’s certainly a mild dissuasion, but a determined pest can safely cross its barrier. So even though copper isn’t exactly a panacea for the prevention of slimy invaders, it does have other important roles to play in cultivation.

Disease Control

In the form of the salt copper (II) sulfate, it’s used as a fungicide. A mixture of this inorganic compound with lime, called the “Bordeaux mixture,” was developed in 1882 and has long been used as a foliar spray on grapes. Mixed with ammonium carbonite, it’s called “Cheshunt compound” and is used to prevent damping-off in seedlings.

But its pest-killing qualities aren’t limited to the fungicidal: It’s antimicrobial, as well.

Important Soil Nutrient

Perhaps most importantly, though, copper is an essential soil and plant nutrient—one that is often under-appreciated until it isn’t there in sufficient quantities. Without adequate supplies, plants look like they have frost damage, with wilting, browning, and delayed flowering or even sterility.

However, don’t go applying copper fungicides and soil amendments willy-nilly. Too much in your soil is hard to fix. Because it’s non-soluble and remains in the soil for years, it will essentially be toxic for plants and other organisms. Ideally, it should be present in the soil at levels of 10 to 30 parts per million (ppm), and soil can be tested to see if more should be added for optimal plant growth.

Copper Tools—The Perfect Plant Supplement

Austrian scientist Viktor Schauberger demonstrated that simply using copper tools in the garden can benefit plant growth. The trace amounts of this soft metal that end up in the soil are enough to give a boost without overwhelming the soil.

Essentially, this mineral is a double-edged sword: It’s both essential and potentially poisonous. It all depends on both how and how much it’s used.

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