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Be a Better Gardener: The secret to fall lawn care: Less is more

Berkshire Botanical Garden’Äôs Tatkon Entry Garden with its lush lawn leading to a collection of annuals and perennials. The lawn is treated minimally and is mowed high to retain moisture.
September 6, 2018 11:45 am Updated: September 6, 2018 11:54 am


Maybe you’re a “freedom lawn” fan — anything goes, as long as it’s green and doesn’t break the lawn mower. That’s fine. Maybe you have higher aspirations for your greensward, but you’re not willing to invest the time and money needed to make your lawn a velvety Kentucky bluegrass carpet, nor are you willing to inflict the environmental costs that such a monoculture involves. Still, you’d like something more than a field of clipped weeds. Fortunately, you can have that good-enough lawn without an excessive amount of labor and materials. Typically, a few timely interventions are all that are needed, and the time for most of them is now.

This is the time to think fertilizer. The popular attitude is that spring is lawn feeding time. That’s when the garden centers put the bags of lawn food out on the shelves, and the ads appear for 4-step programs. The fact is, though, that an early fall fertilization is the most important for grass, and one feeding per year at this time is adequate for the good-enough lawn.

Of course, any lawn fertilization should begin with a soil test. Otherwise it’s like salting a dish before you sample it — you are liable to add too little, which is unfortunate, or too much, which is worse. An inexpensive soil test from your state agricultural university lab will tell you precisely how much nutrients your soil needs. With this information in hand, you can apply exactly the right amount of fertilizer of the right formula — enough to satisfy your lawn’s needs without injecting excess nutrients that will wash away and contribute to water pollution.

One point to keep in mind when shopping for your once-a-year lawn fertilization is that your lawn quite likely won’t need any phosphate or potassium, the second and third numbers in the fertilizer formula. In fact, Vermont, New York, Connecticut and a number of other states restrict by law the amount of phosphates you can apply to your lawn without a recent soil test indicating that they are needed.

It’s also important when shopping for lawn fertilizers to note what types of nitrates (the first number in the fertilizer formula) that the product includes. In general, you want a high proportion of “slow-release” nitrogen, which may be listed as water-insoluble nitrogen (WIN). These nitrates are released more slowly into the soil, at a rate which the grass can better utilize, so that they are less prone to wash away with surface run-off and pollute local streams, ponds, or lakes. A good rule of thumb is to use a fertilizer containing at least 30 percent slow release nitrogen on non-sandy soils and at least 60 percent slow release nitrogen on sandy ones.

Organic fertilizers tend to be naturally slower to release their nutrients as they depend on soil microorganisms to break them down into a form useful to plants. When using organics, make sure that whatever you apply isn’t too high in phosphates, as that can be a problem with animal manures and even with composts.

Another practice that can markedly benefit your lawn is a late summer/early fall aeration. Over time, traffic across the lawn will tend to compact the soils, especially clay soils, so that they are less hospitable to root growth and less able to absorb moisture. The best remedy for this is to rent a core aerator, a machine that pulls plugs of soil from the ground leaving behind a pattern of small holes and a scattering of soil cores on the surface. The plugs can left to dry and then broken up and re-distributed with a rake. Core aeration is best done when the weather has cooled, and the soil is just slightly moist; doing it when the soil is wet will only exacerbate compaction problems.

One final measure to consider is liming. This should only be done at need, when a soil test tells you that your soil is too acidic. I’ve found though, that if the soil is acidic, an application of lime at the rate recommended in the soil test results can have a profoundly positive effect on the growth of the lawn grasses, favoring them at the expense of weeds. Indeed, healthy, vigorously growing grass is the best defense against weeds, and all you really need to ensure your good-enough lawn.

Be-a-Better-Gardener is a community service of Berkshire Botanical Garden, located in Stockbridge, Mass. Its mission to provide knowledge of gardening and the environment through 25 display gardens and a diverse range of classes informs and inspires thousands of students and visitors on horticultural topics every year. Thomas Christopher is a volunteer at Berkshire Botanical Garden.