Fall Lawn and Garden Fertilization
Excerpted from: How to Fertilize Your Garden or Lawn in Late Fall By Kelly Burke
A late fall fertilizer application is a good idea in cold-weather climates where winters are a period of
dormancy. A mild feeding of ornamental garden beds or vegetable gardens can also replenish soil
that has been heavily depleted by growing plants over the season. Late summer and fall are especially
good times to fertilize turf lawns.
Fall is the time when cool-season grasses recover from summer stresses such as drought, heat,
and disease. If the lawn has been properly fertilized in the late summer and fall, turf grass can begin
to store carbohydrate reserves in the stems, rhizomes, and stolons. These carbohydrate reserves
help grass resist winter injury and disease, and serve as a source of energy for root and shoot growth
the following spring. Late fall fertilization will also provide better winter color, enhanced spring
green-up and increased rooting.
Although the exact timing can vary due to weather conditions and climate zone, the final fertilizer
application should be made sometime in November in most regions, at the point when the grass
has stopped growing or has slowed down to the point of not needing to be mowed.
Do not wait until the ground freezes, however. Ideally, there
is still active growth occurring, but not enough to warrant mowing.
Proper timing is essential. If fertilizer is applied too early while grass or garden plants are vigorously
growing, it can invite winter injury and snow mold the following spring. Do not ever apply fertilizer to
frozen soil or over snow or ice.
Nitrogen is the most important nutrient for a fall fertilizer. A recommended dose for lawns: is one
pound of soluble nitrogen for every 1,000 square feet or one and a half to two pounds of slow-release
nitrogen for every 1,000 square feet.
A complete fertilizer with a high ratio of both nitrogen and potassium (K) is essential for enhanced
rooting, cold hardiness, disease resistance, and wear tolerance.
Be wary of applying a fertilizer with too much phosphorus (P), since run-off of this nutrient can be
very damaging to rivers and streams.
For in-depth tutorial on fertilizers: Fertilizer Basics
Lawn Applications: In early fall use a regular lawn fertilizer with N-P-K ratios of 3:1:2 or 4:1:2.
For example, a bag may list 21-7-14 or 32-8-16. Amounts don’t need to be exact but should be similar
to the suggested ratios. Hold off on applying “winterizer” fertilizers until late October or early November.”
The reason that fall fertilizing is so effective is because plants respond to external triggers in fall to
start the process of preparing for winter. These triggers are things like daylength and temperature
changes. As days shorten and air becomes cool, plants — including turf grass — respond by slowing
growth and shifting food reserves from leaves to roots. Although air temperature continues to fall,
plant roots remain active in soil.
Shifting excess nutrients to roots is the secret to plants’ return each spring. Those stored food reserves
fuel the spring wake-up. The same is true of your lawn. By fertilizing grass in fall, you’re feeding the active
roots and giving them even more nutrients to store for winter.
Garden Applications: The recommendations for flower and
vegetable gardens are similar. A mild fertilizer feeding in the fall will replenish the soil and prepare
it for a quicker green-up when planting begins the following spring. Gardens do better with this
approach than with a heavy dose of fertilizer in the early spring.
Too much nitrogen can be as damaging to plants as too little, and using natural sources of nutrients,
such as compost on the garden or mulching lawn clippings rather than bagging them, can replace
some of the traditional chemical fertilizer applications. One late- to mid-summer feeding of a lawn,
followed by a light fall feeding, produces a better lawn than the old recommendation for three or four
major feedings for each growing season
Flower or vegetable gardens similarly can thrive with fewer fertilizer applications than once believed,
especially if they are properly amended with compost and other natural organic materials. Most
gardens do very well with one feeding shortly after planting and one as the growing season
concludes, although plants that produce large quantities of vegetables or very large, plentiful
flowers may need more.
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