Each year, Americans spend billions of dollars on lawn fertilizing to make sure our grass grows green and dense. That includes buying 90 million pounds of fertilizer. “In urban settings, soils are typically lacking the required nutrients for plants and lawns to stay healthy,” says Marc Mayer, Director of Technical Operations at TruGreen. “Soil amendments and fertilizers help to reestablish a nutrient bank in the soil.”

But, we’re probably also overdoing it, says Craig Elworthy, founder of Lawnbright. “Using a large bag of synthetic fertilizer has become a crutch, a shortcut to a great lawn,” he says. “But it’s not sustainable for your lawn or the planet.”

That said, everyone agrees that a little nitrogen can be good for thickening up your lawn and crowding out weeds. Here’s how to find that perfect balance when it comes to lawn fertilizing.

When and How Often Should I Fertilize My Lawn?

It depends on where you live and the type of grass and fertilizer you’re using. For many, that means starting in the spring. “In the spring, apply just enough fertilizer to help green up your lawn,” says Churchill. “About half the normal amount will do.”

If you have a cool-season lawn like Kentucky bluegrass, perennial ryegrass or tall fescue, fall is another key time to apply nutrients. This will help replenish food reserves after a year of growing and before winter sets in. For warm-season lawns, like bermudagrass and centipede grass, you’ll want to fertilize during the summer and apply potassium in the fall to help the turf through the winter, says Mayer.

Elworthy, who lives in Massachusetts, applies a slow-release organic liquid fertilizer every eight weeks, starting in late April. He also mulches his clippings, which cycles nutrients back into the soil.

“Since I mulch the clippings, I only need to use a small amount of actual fertilizer a few times during the growing season,” he says. “Healthy soil, mowing and watering are much more important for a healthy lawn, so if you can get those cultural practices right, you hardly need much fertilizer at all.”

When To Call a Pro

It can save some hassle to consult a pro at least once, to learn a good regimen for your particular situation. “Lawn care is rarely, if ever, one-size-fits-all, and the same goes for fertilization timing,” says Mayer. “Homeowners can tap a lawn care professional to plan a proper fertilization regimen that’s tailored for their lawn.”

Other reasons to call a pro include:

• Unexpected weather, like flooding, drought and freezing
• If you need heavy machinery, like aerators
• If you have a very large lawn, or a large renovation planned
• If you travel a lot or are otherwise short on time