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Q: Help! Last year our lawn looked a little too brown for my liking. When should I fertilize our grass to ensure a lush, green lawn this year and the next?
A: As the saying goes, “The grass is always greener on the other side of the fence.” But if this year you want that green lawn on your side, fertilizer can be an effective ally. Generally speaking, you should fertilize your lawn at least twice a year to ensure good overall health and keep your grass looking its greenest. But if you fertilize at the wrong time or over treat your lawn, you could encourage weed growth or possibly burn the grass. To avoid damaging your lawn, before you begin a fertilizing routine consider this rule of thumb: The best time to fertilize is when your grass is actively growing—and this, in turn, is determined by where you live and what type of grass you have. So, to figure out when you should fertilize, you need to know your grass type, your growing zone, and the best fertilizer for the job.
The first step is to identify your grass type. Within the United States, there are two types of grasses: warm-season grasses and cool-season grasses. As well, a large cross section of grasses are considered transitional, which means that they can be grown successfully in the central portion of the country, a region that is typically too warm for cool-season grasses and too cool for warm-season grasses. Your fertilization schedule will depend on the type of grass you have, but remember that it takes constant commitment to any routine to guarantee year-after-year success.
• Cool-season grasses are prevalent in the northern parts of the United States, and varieties like Kentucky bluegrass, tall and fine fescues, and ryegrass are the most common. Cool-season grasses prefer lower temperatures and have two peak growing periods: one in the early spring, just after winter dormancy, and another in the early fall. High summer temperatures and lack of water may cause cool-weather grasses to go dormant until chilly temps arrive and water is more readily available.
• Warm-season grasses thrive in the southern region of the United States. These grasses are tropical in origin and benefit from warm temperatures, which means that midsummer is their ideal growing season. These grasses are tough, and they form a thick lawn cover that becomes denser over time. The four major types of warm-season grasses are Bermuda grass, centipede grass, St. Augustine grass, kikuyu grass, and zoysia grass.
• If you live in a transitional zone, you may have a combination of warm- and cool-season grasses that will require different care at different times. A clue to figuring out your grass type is to keep a lookout for how your lawn behaves. Warm-season grasses will turn brown after the first frost, while cool-season grasses will generally stay green all year long in the cool and transitional zones. They will not, however, survive the summer months if the temperatures become excessively high.
Once you identify your lawn type, you can figure out when to feed your grass. Each type of grass has its own growing season and requires a different fertilizing schedule.
• The primary growing period for cool-season grasses is during the spring and fall when average temperatures are between 60 and 70 degrees Fahrenheit. To ensure optimal health, fertilize heavily in the fall and lightly in early spring. You can choose either slow- or quick-release fertilizer types, but be sure to apply the treatment before the temperatures peak in summer when these grasses will most likely go dormant. Cool-season grasses need only one to two pounds of nitrogen-rich fertilizer per 1,000 square feet per year. As you’re planning out your lawn-care routine, note that there are special winter fertilizers available at your local gardening center that are formulated to help protect your grass during the cold months.
• The optimal growing period for warm-season grasses is late spring and summer, when temperatures average 80 to 95 degrees Fahrenheit. As growth may begin below or above this temperature range, keep an eye on your lawn and apply the fertilizer just as the grass starts turning green in the spring. Warm-season grasses should be fed three to four pounds of nitrogen-rich fertilizer per 1,000 square feet of lawn per year. You can choose between slow- or quick-release fertilizer types, but be sure the application is fully absorbed before the onset of high temperatures. After applying the fertilizer, water the grass thoroughly, washing the grains off the blades of grass and into the soil to be sure that the soil fully absorbs the treatment. Apply a second round of fertilizer once the peak summer heat has passed.
Additional Tips for a Lush, Green Lawn
• Avoid applying nitrogen-rich fertilizer when your lawn is dormant. Nitrogen, a key component of fertilizer, contains a growth stimulant that could increase unwanted weed growth if applied during dormancy. If you’ve endured a long winter and the grass is not yet growing, don’t be afraid to delay your scheduled treatment.
• Read the label before buying fertilizer to find out how long it is formulated to last. Some time-released brands will slowly distribute nutrients over a two- to eight-month period, so leave sufficient time between applications to avoid over fertilization, which could damage your lawn.
• Avoid fertilizing your lawn during periods of drought. Most fertilizers need several waterings to soak into the soil, and allowing the fertilizer to sit on top of the lawn could burn the grass. If you intend to feed your lawn in August and there are watering restrictions in place due to drought, you may want to delay the application until the cooler weather arrives.