Over the years I have defined a difference between a “Fall” lawn fertilizer and a “Winterizer” fertilizer. These two types of fertilizer really address the root growth and winter hardiness of Kentucky Bluegrass.
Physiologically, grass produces an excessive amount of new roots in the spring and also in the fall when the temperatures are cool, soil moisture is high and primary nutrients for root development are readily available.
Roots of Kentucky bluegrass develop from the underground nodes of the rhizomes and from the basal nodes of the above ground shoots called the crown. Roots also develop at the terminal nodes of rhizomes that emerge above the soil as shoots.
Root growth is greatest in fall, followed by the spring period and slows to almost stops during the high heat in the summer. Root growth of Kentucky bluegrass peaks at soil temperatures of 60F and declines sharply as temperatures rise above 70F. Root growth practically ceases at temperatures above 80F.
FALL fertilizer should be applied when the soil temps start to hit 70 degrees until the soil temps reach the 55 degree mark. A true Fall fertilizer is designed to build new roots for the grass plants by supplying additional phosphorus (P) and Potassium (K), which are the primary nutrients needed to produce new healthy roots. This dose of “P & K” stimulates and supports new root growth, so your lawn is able to “dig in” and get ready for the cold weather. Fall fertilizer also prepares your lawns root to utilize 100% of the Winterizer fertilizer which should follow 4-5 weeks after the fall fertilizer application.
Carbohydrate accumulation and storage in these newly formed roots is the name of the game when it comes to the next stage of nutrient that will be applied.
WINTERIZER fertilizer on the other hand is a fertilizer which is intended to be applied after the grass plant has created all those new, EMPTY roots and just before the ground freezes solidly (or in the case of cheep skates, the one of two application of fertilizer they offer their lawn each year). It is also possible to have this fertilizer activated by those first of the season,wet snow storms or the rains that always come a few weeks prior to that first snows that stick. So In other words, Don’t be concerned with keeping your sprinkling system up and running into December just to water in or activate the winterizer application.
The role of this HIGH NITROGEN ( 1.5 – 2 pounds of active Nitrogen per 1000 square feet) application is to supply the maximum amount of nitrogen that can then be converted into stored, usable carbohydrate before the soil freezes up. This application helps feed the plant through the winter in the southern areas or prepares the cool season grasses for the longer winter ahead. Another benefit from this application is the EARLY Greening Up of your lawn or clients lawn next spring.
To summarize, Carbohydrate accumulation in rhizomes peak in late fall when “above ground” or shoot growth of Kentucky bluegrass slows. As temperatures become favorable for growth in the spring, these carbohydrate reserves become available for development of new shoot growth again.
In essence, this application will “tuck your lawn into bed” and keep it safe during the long, harsh winter allowing it to emerge in the spring as the Champion that all your neighbors will be envious of! Green with Envy!