University of Vermont Extension 
Department of Plant and Soil Science

Fall News Article


Dr. Leonard Perry, Extension Professor
University of Vermont

Faced with life outdoors all winter in our cold north, a lawn needs all the help you can give it.  A home lawn is not too particular about its requirements, but by following a few maintenance practices in the fall you can help it survive the winter in good health.

As leaves begin to fall, remove them long before snow arrives.  They not only shade the grass during late fall, but become wet and mat down to smother the grass over winter.  Wide broom rakes are most common, but some use powered leaf blowers.  Raked leaves make an excellent mulch on the bare, winter garden.  They can prevent weeds next year, and as they decompose add organic matter to the soil.  Or add them to the compost pile.

Some run over the leaves with a rotary mower, shredding them into fine pieces.  Unless too thick, or adding to an existing thatch problem, this may work for your lawn.

Continue to mow your lawn until growth ceases, often sometime in October in USDA zone 4 gardens, November in zone 5 and 6 gardens.  Make the last mowing a notch or two lower, in order to remove much top growth.  This will avoid the need to rake off dead growth in the spring, and will help prevent snowmold disease.
If snowmold has been a problem in the past, you may expect repeats on a yearly basis.  Even if you don't recognize the disease, you probably have seen its symptoms-- patchy dead areas all over the lawn which persist after most of the grass has greened up in early spring.  Snowmold is a white growth seen in early spring, resembling snow.  It flourishes on bentgrass-- a main grass in many lawns.

Shorter days and lower light levels in late summer and fall, coupled with cooler nights and increased rain, bring out new forms of fungus problems.  Toadstools and mushrooms are fruiting bodies of soil fungi that live beneath your lawn as white, cobweb strands called "mycelia".  Fungi are plants, but lacking chlorophyll, they can't make their own food as green plants do.  So they obtain energy from organic sources.

Fungi often grow in arcs or circles around a bit of wood buried in the soil.  Their location is evident because they fix nitrogen from the air, and share it with lawn grasses.  This makes a ring of greener foliage, called "fairy rings".  These are especially obvious when mushrooms are showing.  Remove the woody source of food, and the fungi will die and be controlled.

Fall is also the time you find rust diseases on some grasses, especially if you've gotten behind in mowing and they've gotten taller than normal.  These are evident as rusty colored pustules on leaf blades.  You may use fungicides, or merely get grass mowed back to a proper height.

If grass does get too tall, don't mow down all at once, rather lower the mowing height in stages.  This will take another mowing or two, but will cause less stress to the grass and so less chance of disease.

Powdery mildew, that whitish growth on leaves, can also appear on grasses in fall as it does on lilacs, some perennials and some annual flowers.  Infections may be severe enough to kill some bluegrass varieties, but fescues seem immune.  This points to a reason to have diversity in your lawn-- if one has a problem, others are there to compensate.

Lack of sunlight, high moisture, and poor air movement are all conditions conducive to powdery mildew.  So look for it in shady places as under roof overhangs and in tree shadows.  If the weather is cloudy for prolonged periods, you may find it even in the open.  Once again fungicides can be used, or you may reseed with resistant fescues and bluegrass varieties.

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