When to apply fall fertilizer
Late fall fertilizing is a crucial last step in lawn care programs north of the transition zone. Although the exact timing can vary due to weather conditions, the final fertilizer application should be made sometime in November - when the grass stops growing or slows down to the pint of not needing to be mowed, but before the ground freezes.
Proper timing is essential. If fertilizer is applied too early, while grass is actively growing, it can invite winter injury and snow mold. Do not apply fertilizer to frozen soil or over snow or ice.
Why is fertilizing in the late fall important?
Cool season grasses recover from summer stresses like drought, heat, and disease in the fall. If the lawn is not hungry and has been properly fertilized in the late summer, grass can begin to store carbohydrate reserves in the stems, rhizomes, and stolons. Carbohydrate reserves help grass resist winter injury and disease, and serve as a source of energy for root and shoot growth the following spring. A late fall fertilization will also provide better winter color, enhanced spring green up, and increased rooting.
How much fertilizer is needed?
Nitrogen requirements are the most important aspect of a fall fertilizer. It is recommended that 1lb of soluble N/1000 square feet or 1.5 - 2lb of slow release N/1000 square feet be applied. A complete fertilizer with a high ratio of N and K is recommended. K (potassium) is essential for enhanced rooting, cold hardiness, disease resistance, and wear tolerance.
For example, an acceptable fertilizer blend would be 24-4-12 with IBDU. A small amount of nitrogen is immediately available to the plant while the rest is in slow release form, allowing it to slowly break down and provide an extended feeding to the grass.
Late fall fertilizing should be applied in conjunction with a complete lawn care fertilizer program for best results.