University of Vermont
Department of Plant and Soil Science
Fall News Article
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
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
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
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
Return to Perry's Perennial