Greenwashing in the garden

Garden center shelves are stocked with products that promise to make your plants grow taller, produce more fruit or get rid of garden pests. There are even sections of "green" products that claim to be safer for the environment -- and for us.

While plenty of these products are indeed organic and sustainable, others are not. And, unfortunately, you can't rely on the name of the product or the manufacturer's claims to tell you which is which. You have to look for the list of ingredients -- often in small print -- to determine whether a product really is good for the environment.

Here are some of the most common ingredients in fertilizers and pesticides that are not eco-friendly, as well as alternatives that are.

FERTILIZERS

QUESTIONABLE INGREDIENTS

Bat guano

While it is organic, bat guano (otherwise known as bat pooh) is not sustainable. It must age in an arid location, such as a cave, for decades before it can be harvested. The harvesting process disrupts the delicate ecosystem of the cave and deprives the other creatures living in the cave of an essential source of nutrients. Additionally, shipping bat guano from Jamaica and other faraway places requires a great deal of fossil fuel.

Rock phosphate

As its name suggests, rock phosphate contains a high concentration of phosphate, which makes it a popular organic fertilizer. However, it's found in only a few places in the United States, mostly Florida, where it's strip-mined. Because reserves are limited, rock phosphate isn't a renewable resource. Another reason not to use it? Most soils in Minnesota have plenty of phosphate.

GOOD ALTERNATIVES

Corn gluten meal

This waste product from the corn industry is a component in some fertilizers, but it also is sold by itself. Corn gluten meal is renewable and can be harvested without damaging the environment. It's a particularly good fertilizer for lawns because it also helps to reduce weeds, which in turn reduces the need to use herbicides. One note: It typically takes two or three years of use to see the best results.

Cotton seed meal

Another waste product, this meal comes from cotton seeds that have been pressed for their oil. It has a balance of nitrogen, phosphorus and potassium, making it appropriate to use on almost any plants in the garden.

Bone meal, blood meal, feather meal

These byproducts of the meat industry are excellent fertilizers. Feather meal and blood meal are high in nitrogen, making them a good choice for most plants. Bone meal is high in phosphorus and calcium, making it a good choice for tomatoes, which use a lot of calcium.

Milorganite

It's got a clever name (an amalgam of Milwaukee and organic) and comes from a very renewable resource: sewage sludge. Even better, Milorganite not only fertilizes, it also helps repel deer, rabbits and other mammals.

PESTICIDES

QUESTIONABLE INGREDIENTS

Copper

Copper is found in many so-called organic fungicides, which are designed to help control plant diseases. While it's very effective at controlling diseases, it builds up in the soil over time and can poison earthworms and inhibit the growth of certain plants.

Pyrethrum

This insecticide comes from a type of chrysanthemum. The problem is that it kills good insects as well as bad ones. In addition, the EPA has identified pyrethrum as a possible carcinogen.

GOOD ALTERNATIVES

Sulfur

Fungicides containing sulfur aren't usually as effective as fungicides with copper, but sulfur is much safer for the soil and works on a wide variety of diseases.

Insecticidal soap

Insecticidal soap is as effective as pyrethrum and, because it's made from plant- and animal-based oils, it spares many beneficial bugs, including lady beetles (which attack bad bugs) and bees (which pollinate).

Jeff Gillman, an associate professor of horticulture at the University of Minnesota, is the author of several gardening books.