The summer is heading for fall, and it’s time to fertilize lawns. Go to any garden center and you’ll see piles of name brand lawn fertilizer, complete with directions on the back. Just follow these simple steps and you’ll have a healthy, green, weed-free lawn.

What these manufacturers don’t take into account is that different parts of the country have different soils. What may be excellent advice for Pennsylvania or Maine may not work for Colorado. Unlike much of the north and east, the Front Range loses more water to evaporation than it gains in rainfall. Combine that with the native rock from which our soils are derived, and we typically have soils that are alkaline, high in phosphorus and potassium, and low in organic matter and nitrogen.

However, not every yard is the same. Most new housing developments are totally devoid of topsoil. It was scraped off and sold before the foundations were laid. (Of course, you can buy it back, for a price.) After years of irrigation, older gardens may have more acidic soil. And the amount of nutrients depends heavily on what you and the landowners before you have added in the way of amendments.

Turf grasses need plenty of nitrogen, and the best time to apply it is in the late summer and fall. Too much nitrogen added during the hottest time of the summer stresses cool season grasses, such as fescue and bluegrass, by encouraging them to grow when they’d rather be sitting in the shade with a tall glass of lemonade.

As the nights become longer and cooler, these grasses perk up and are ready for a growth spurt. Now it’s time to give them that nitrogen.

As you look at the fertilizer bags, you’ll see that most products contain not only nitrogen, but also phosphorus and potassium. This could be a problem. In soils already high in both these nutrients, adding more year after year can build the levels to the point of toxicity. Too much of anything can be harmful.

In addition, the excess nutrients are picked up by heavy rains or irrigation, where they either contaminate the runoff that ends up downstream, or soak into the groundwater. Now that most factories have cleaned up their acts, it’s believed that contaminated runoff is the main source of pollution of our rivers and streams.

Colorado State University’s Turf Program has a website that provides detailed instructions on caring for your lawn. Or start directly with fact sheet 7.202, “Lawn Care” for basic information. Most of the information in this sheet is accurate, and I highly recommend following their directions.

Unfortunately, like most lawn advice, the paragraph encouraging the use of balanced or complete fertilizers was written before recent research demonstrated how over-fertilized most American lawns are. In our pursuit of the perfect patch of green, we’ve all become NPK junkies. I hate to sound like a broken record (remember what those are?), but the only way to know which nutrients your lawn needs is to get a soil test.