While 2020 is a year like no other, that first evening chill and the initial hint of color in the trees signify fall is, once again, on its way.

Those signs should also be a trigger for us to think about what actions we need to take in our yards to keep the grass healthy throughout winter and into next spring. To do this, it is helpful to understand how grass gets its nourishment. Cool season grasses that we have here in the Lake Champlain basin grow most readily between 40-75 degrees.

That means that, not only does grass have a spurt of growth in the spring, it also has another growth period in the fall. This is important to help it prepare to survive winter. Grass grows through the process of photosynthesis. That is, it uses the sun’s energy to create not only oxygen, but sugars — some of which it stores at its base for nourishment during summer droughts and winter dormancy periods. Late summer and fall provide plentiful opportunity for grass to continue to photosynthesize, storing sugars for use in winter.

Stored sugars are only part of what grass needs to be healthy, however. It also needs other nutrients. Leaving grass clippings to decompose in place after mowing is effective at returning some nutrients back to the soil for plant uptake. Another action to take to help keep grass healthy is to conduct a soil test. This allows you to assess if grass has a need for additional nutrients. If it does, and if you opt to add those using fertilizer, that is best applied in the fall.

This timing allows slow-release nitrogen in the fertilizer to nourish the grass over many months, helping roots develop more fully, which, in turn, helps keep grass healthy. It is important that fertilizer be added to grass only after a soil test has been completed. This is particularly important, as, in Vermont, fertilizers that contain phosphorus can only legally be used on lawns if a soil test confirms phosphorus is needed or if a new lawn is being established.

Knowing this, you might then wonder, how do I get my soil tested? Luckily, the UVM Agricultural and Environmental Testing Laboratory provides easy-to-understand directions on its website to guide landowners through the soil sampling process. The Lab also analyzes soil samples and provides site-specific recommendations for fertilizing your lawn based on the results.

Lab guidance suggests that those without a soil probe can sample soil using a trowel or shovel. They recommend collecting soil samples from at least 10 locations in your yard, following a zig-zag pattern across the area of interest. At each location, use the shovel or trowel to cut out a triangle of lawn, digging to about 4-6 inches deep. Set that triangle piece of earth aside. Then use the trowel or shovel again to remove a narrow slice of soil from one edge of the hole. Brush away the soil on the outer edges of that slice, and put the 1” center strip of that slice of soil into a bag. Replace the triangle piece you had set aside into the hole. Then move to the next location in your zig-zag pattern. Follow the same procedure to collect the remaining samples, adding them to the bag. Once all 10 samples are collected, mix them to form a uniform composite sample. You can download and print a form from the Lab website to complete. Send your completed form, your soil sample and payment to the lab. You can expect results in a few weeks.

By limiting any addition of fertilizer to only what your lawn requires, and doing so in the fall only, you can help keep local water bodies clean.

This column, expected to continue monthly in this paper, will feature information about actions you can take to help protect local waterways and the science behind those actions. It is written by staff from organizations that partner on a collaborative effort called Lawn to Lake. You can learn more about the lawn mowing best practices and fertilizing regulations described above, and the simple message, “Don’t P on your lawn” at the Lawn to Lake website.


Today’s article was prepared by Kris Stepenuck, Extension Assistant Professor in the Rubenstein School of Environment and Resources at the University of Vermont.

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