Is Winterizing Bad for Grass Seed?

Cool Season Grass

• Cool season grasses like fescue and Kentucky bluegrass do well when they are sowed in late summer and early fall. These cool grasses prefer cool nights. Low temperatures optimize their growth. When seeding your lawn with cool season grass, choose a winterizing fertilizer formula that is low in nitrogen and high in potassium. Potassium encourages root growth. High nitrogen fertilizers have the potential to damage seeds, regardless of season.

Warm Season Grass

• Warm season grasses like St. Augustinegrass and centipede grass go dormant in the winter months. Fertilizing these grasses near the end of their growing season will encourage new growth that is incapable of withstanding frost. This increases the potential for lawn damage. Warm season grass seeds are usually planted in spring, when they can better establish roots and thrive in their preferred warm temperatures. If you choose to sow warm season grass seeds in the late summer or early fall, refrain from applying a winterizing fertilizer and avoid encouraging early germination.

Fertilizers

• Winterizing fertilizers are normally higher in potassium than nitrogen. Determine the best fertilizer for your lawn by reading the formula ratios. The first number indicates the amount of nitrogen available in the mix, the second number shows the amount of phosphorous and the last number indicates the amount of potassium in the mix. If you choose to apply a high nitrogen fertilizer, apply it at least two months before the first freeze. Mature cool-season grass will benefit from the additional spurt of carbohydrate-fueled growth. High nitrogen fertilizer should be applied first, then the lawn should be irrigated. Seeds should be planted last.

Considerations

• High potassium fertilizers, when applied throughout the growing season, will help increase warm season grasses' cold tolerance. Before applying a fertilizer to any type of lawn, conduct a soil test. Soil tests provide information about your soil's deficiencies or nutrient overages. This is especially important information to have before applying fertilizer. Too much potassium burns warm season grass blades. If you have applied enough fertilizer during the growing season, you may risk burning your grass when applying winterizing fertilizer.