Craig Aston, senior lecturer at USU and co-owner, A&D Landscaping
Lots of nitrogen fertilizer in the spring may make a lawn green and beautiful, but may not be best for the lawn in the long run. I’m not suggesting that nitrogen fertilizer is not good for your lawn. It is by far the most important nutrient for turf. But, when used too heavily in the spring, or when used as the only management tool, it may result in a weak lawn during the summer. I’ll explain some basics about putting your lawn on the defensive by making and keeping it healthy and vigorous.
When a lawn is thriving, most pests and stress can’t. For example, a thick healthy lawn, mowed at the correct height and watered properly will keep most weeds from germinating and help the turf to out compete with those that are already there. There are three basic principles, or rules, to follow to keep your lawn healthy, strong and defensive.
- First, fertilize properly. Most cool-season lawns need between three and four pounds of total nitrogen per 1,000 square feet each year. It is best to apply that fertilizer throughout the season, not just in a big, heavy dose in the spring. Although this may make the lawn look great for several weeks, it will weaken the root system and make the lawn quite weak during the heat of the summer when pests and weeds are attacking. The best way to fertilize is to evenly distribute the nitrogen throughout the growing season. A commonly recommended fertilizer program would be to apply fertilizer in early Spring (1 to 1.5 lbs around April 15), early summer (.5-1 lbs mid-June), late summer (1 lb around Labor Day) and late fall (1-1.5 lbs mid-October). If you don’t know how to figure those rates then just use a good 4-bag fertilizer program (which most garden centers provide), and it will probably give you similar rates that will uniformly feed your lawn.
- Second, water properly. While it is true that lawns require a lot of water, many lawns are actually over-watered. It’s not uncommon to see lawns with the sprinklers coming on every day or every other day. While this may keep the lawn looking pretty good, it actually makes the lawn weaker. The best way to water your lawn is deeply and less frequently. For example, the USU Extension service recommends applying about two inches of water per week during the hottest part of the summer, and using less than that in spring and fall. It is best apply about one inch of water every three to four days, not daily. This drives the water deeper into the soil (about 6 to 8 inches), encouraging deeper root growth and allows the lawn to dry out a little between waterings, which helps reduce some insect pests. A deeply rooted lawn tolerates the heat better and can fight-off pests and other stresses more effectively.
- Third, mow properly. Kentucky Blue grass, which is the most common grass in the intermountain area, prefers to be mowed at a height of about 2.5 inches. This may not look quite as manicured as a tightly mowed lawn, but it is better and more healthy for the lawn. It allows the lawn to be thicker, stronger, and more resilient, helping the lawn to fight off weeds and pests more effectively. Also, mow your lawn frequently so that you are never removing more than about 1/3 of the total blade, or height of the grass, with each mowing. Therefore, you should mow your lawn when it is about 3.5 inches tall. If you wait until it is taller you will remove an unhealthy amount of the leaf surface, stressing and weakening the lawn significantly.
If you properly fertilize, water, and mow your lawn it will be on the offensive in defending itself from weeds, pests, and stress. It will have a thicker, more healthy, crown which can prevent weed growth. It will have deeper healthier roots which can get by with less water while tolerating heat stress and insect invasions more successfully. And it will be nicer to look at and more enjoyable to be on.