Once again, when fertilizing a lawn, most important nutrient for fertilization is NITROGEN. The nitrogen applied in the fall is the the most important because… Because the nitrogen applied in the fall promotes root growth over the winter months. Use a high-nitrogen fertilizer, such as 25-5-5 or something with a similar formula. Many retail stores stock winterizer that is high in phosphorus and potassium because many people think these nutrients are important to winterize your lawn. Because we are in Flagstaff where only cool -season grasses grow, there is no benefit to adding extra phosphorus and potassium in fall to COOL-SEASON grasses. Many of the garden stores in Flagstaff are chain stores which supply fertilizers to many different zones across the country, because of that high-nitrogen lawn fertilizer may not be readily available at this time which leaves two options.
1. Using your left-over high nitrogen fertilizer from earlier applications.
2. Make your own, using this formula! urea (46-0-0) at 2 lbs/1000 square feet or ammonium sulfate (18-0-0) at 5 lbs/1000 square feet.
To take care of your cool-season lawn you will need to prepare yourself for the fall fertilizing by buying extra high-nitrogen fertilizer when fertilizing earlier in the year. Store it in dry cool conditions, then apply it in fall at the end of the growing season. The best time to fertilize your lawn is when the grass is still green and 2-3 weeks before the ground typically freezes. Your typical range is from October 15th to the first week in November. Best of luck!!!
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