University of Vermont
Department of Plant and Soil Science

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FALL LAWN CARE

Dr. Leonard Perry, Horticulture Professor Emeritus
University of Vermont

Proper lawn care in fall, including mowing, fertilizer, and watering, will help it survive winter in good health.  It will be able to resist diseases and weeds better next season, and to start off next year in good shape.
           
As long as the grass is growing, keep mowing, and mow at the proper height.  This is often the most misunderstood and abused part of lawn care.  Most grasses should be mowed at 2 to 2-1/2 inches high in spring and fall, and 3 to 4 inches high in the heat of summer.  The last mowing of the season can be on the short side, about 2 inches high.  This will help prevent the grass packing as much under snow, making it susceptible to leaf diseases such as snow mold.
           
Another aspect of mowing height is not to cut off more than one third at any mowing.  So if the grass gets too tall, decrease the height to the ideal in a couple of mowings, the first being higher.  This way you won't have an excess of long grass clippings that may cause thatch, and you can leave them on the lawn-- a good practice as these recycle nutrients and organic matter back into the soil.
           
Higher mowing is important to grass for at least two main reasons.  More leaf area on grass plants means they'll be able to make more carbohydrates needed for healthy growth.  There is a direct relationship too between the amount of tops and roots.  The more tops to the grass plant means more and deeper roots, which in turn means the grass can better withstand stresses.
          
It is important to send the grass into the winter as healthy as possible, which means that adding fertilizer in early fall is important; in fact, this is perhaps the most important fertilizer application during the growing season.  Add about one pound of actual nitrogen per 1000 square feet of lawn.  So if a fertilizer is 10 percent nitrogen, you would add 10 pounds of this product over each 1000 square feet (5 pounds of a 20 percent fertilizer).  You'll want a quick release fertilizer so the grass can take it up before winter.  Most of slow release fertilizers will be lost in the soil (or worse into watersheds) over winter when the grass isn't growing.
           
If you haven't tested your soil before, or in a few years, now is a good time.  The results will tell you if any other fertility or lime is needed.  As many soils become more acidic over time, lime is often needed to keep the soil acidity or pH between 6.0 and 7.0.  Add lime in the fall as it is slow acting, and its effect won't be fully realized until spring.  Soil test kits are available from many full-service garden stores and your local university Extension offices.
           
In addition to proper mowing and fertility, watering is key to helping your lawn go into winter healthy and without stress.  If rain is infrequent or too light, make sure the lawn receives at least an inch of water a week.  This is where an inexpensive rain gauge from a garden or hardware store comes in handy.  Or you can get a more elaborate wireless rain gauge from complete garden suppliers.  Often during a rainy spell you may think you're getting more rain than really is falling.
          
If you've been using the lawn during the growing season, with lots of foot traffic, play, or even driving on it, the soil is likely compacted and could benefit from aeration.  This simply involves penetrating the surface with holes so air, water, and nutrients can reach the roots.  One simple method is to use "aeration spikes" you can buy in garden stores and catalogs that slip onto the bottom of your shoes.  As you walk on a lawn these break through the compacted surface.  Or you can rent a special aerator machine from rental firms, or hire a professional lawn
care firm.
           
Once aerated, or if the soil is fine without this, overseed if your lawn is weak and needs a bit more grass.  Buy a good grass seed blend of varieties, scatter it as needed over a sparse lawn or bare spots, and water in.  Grass seeds get established more quickly during the cool fall than hot summer, and now when pressure from weed competition is low.
           
Another misunderstood part of lawns relates to thatch-- a mat of living and dead stems and roots on the surface that slows water, nutrients, and air from entering the root zone.  This is not caused by short grass clippings, but often by improper culture or environmental conditions.  If this thatch layer is more than an inch thick, consider renting a dethatcher machine, or hiring a lawn care professional to help with this.
          
If you have broadleaf weeds, spot treat or dig out.  There are special tools just for the deep roots of dandelions.  I have a friend who plants a sprig of thyme in each hole made where a dandelion root was dug.  This will create a nice aroma over time as you walk through the lawn.  There is no need to use a general herbicide product now, as many work on grass seeds which aren't growing, and it may kill lawn grass seeds you put down.
           
Once you reach the end of grass growing and mowing season, early October in colder areas and later in warmer ones, make sure you keep leaves raked up as they fall.  Otherwise these will smother the grass.  Use your leaves for compost, or for mulching beds.  Many like to run over them first with a mower to shred them, or put them through a shredder that you can buy just for garden clippings and leaves.  I pile mine on a future garden area, covered with some poultry wire to keep them from blowing away.  As they break down they'll make great organic soil.      
     

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