Soil test results should always be considered before designing a fertilization program. Cool-season lawns, Kentucky bluegrass, perennial rye, tall fescue, fine fescue, require a fertilization program that concentrates on root growth in the spring to prepare for summer stress such as drought, heat, and disease pressures. Top growth is always positive for any lawn, but a cool-season precautionary measure is not overloading turf with nitrogen during stressful periods. Therefore, it is essential to select a fertilizer that will meet the following goals:
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Encourage strong root growth after winter dormancy
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Support moderate shoot growth without excessive nitrogen
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Improve turf density
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Enhance overall turf vigor and quality
Cool-season lawns will encounter shallowing of roots once the temperatures rise above 80 - 83 degrees fahrenheit as the turf goes into defense mode. Upon entering the stressful summer months, turfgrass will burn a lot of energy, and the roots will become shallow due to the increased soil temps. The roots can die off significantly during this time frame, making it harder for the plant to survive. Applying high percentages of nitrogens during the summer on cool-season grasses will increase top growth that shallow rooting cannot sustain, and the plant can die at the surface. However, cool-season grasses need energy sources to survive and save as much energy as possible.
Raising the height of the cut, irrigating profoundly and infrequently, and fertilizing with balanced fertilizers are strategies for protecting cool-season grasses in the hot summer months. The higher leaf blades make the soil more insulated and keep it cooler. Therefore, growing the roots as deep as possible in the spring increases root depth and reduces root shallowing.
The Best Fertilizers for Cool-season Grasses in Spring
Simple Lawn Solutions 16-4-8 is a great selection for spring as it has 16% N, 4% P, and 8% K. This will give the lawn good color enhancement, increased rooting depth, and increased stress tolerance with potassium. 16-4-8 also contains phosphorus, promoting ideal conditions for root growth without excessive top growth. 15-0-15 is another excellent application as it will strengthen roots before summer stress.
Depending on the soil type used as a growing medium, keep nitrogen applications to ½ lb. - 1 lb of N per 1,000 square feet. Using slow-release fertilizer is another good option, as it allows the nutrients to be gradually released over time as opposed to all at once. Avoid high nitrogen applications early if applying pre-emergents because it may reduce the effectiveness of weed control.
Overseeding lawns in the spring would greatly benefit from applying Simple Lawn Solutions Root Hume, Soil Hume, and Sea Hume as part of a cool-season fertilization program, supporting nutrient uptake and fertilizer efficiency.
The Best Fertilizers for Warm-Season Grasses in Spring
Warm-season grasses, Bermudagrass, Zoysiagrass, St. Augustinegrass, Centipedegrass, Bahiagrass, require proper fertilization in spring to support green-up, root development, and strong growth before summer. Warm season goals are similar to those of cool season grasses:
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Promote green-up after winter dormancy
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Support strong, deep root growth
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Balance nitrogen applications to prevent thatch build-up
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Enhance overall turf vigor and quality
Although warm-season grasses are under much less stress in the late spring and summer than cool-season grasses, applying high percentages of nitrogen is still not recommended as it can produce rapid top growth and limited root growth. Root growth is always the main focus for the overall health of the lawn, supported by the old saying, “firm roots are vigorous plants.”
16-4-8 is also an excellent fertilizer to start the season in warm-season turfgrass areas. It encourages steady growth and contributes less to excess thatch build-up. Using Simple Lawn Solutions Lawn Booster 6-0-0 is great for deepening the green color of the lawn with nitrogen and iron, with the absence of phosphorus and potassium. 28-0-0 can be utilized on warm-season turfgrasses as well, on select varieties like zoysia, requiring less nitrogen lbs. per year than Bermuda.
Wait until the warm season grass has started to green up before applying fertilizers. Use balanced NPK fertilizers for root and shoot growth, like 16-4-8 or 15-0-15, applying ½ lb. - 1 lb. per 1,000 square feet. In early spring, avoid high phosphorus fertilizers unless seeding or planting sod. Regardless of being a cool season or a warm season, Root Hume or Soil Hume are bonus applications that increase nutrient efficiency, microbial activity, and specific stress tolerances.
The Benefits of Micronutrient Fertilizers for Grass
Applying a micronutrient fertilizer, such as Simple Lawn Solutions Microbooster, will deepen the lawn's color and enhance overall turf quality. This product contains micronutrients iron, manganese, and zinc. Iron is a micronutrient that enhances turfgrass color, metabolism, and overall health. Unlike high-nitrogen fertilizers, iron does not promote excessive growth and converts sunlight to energy.
Manganese is an essential micronutrient that supports photosynthesis, root development, and stress resistance in turfgrass. Zinc also enhances stress resistance, enzyme activation, and chlorophyll production, all essential nutrients increasing benefits in growing and maintaining the lawn.
Other Tips for Fertilizing Cool and Warm-season Grasses
Specific product recommendations should be based on your soil test results. A great option for both cool season and warm season grass fertilizer is 16-4-8. New, overseeded lawns can have an increase in phosphorus such as 6-18-0 Growth Booster fertilizer. For weed prevention, a combination of fertilizer and pre-emergent weed control works well together. Using organic fertilizers is always an option, but the turfgrass response may -be slower.
