Kentucky Bluegrass should be fertilized in 3–4 stages from spring through fall. Your first application of fertilizer should be in March or April, as the grass begins to green up. Then, periodic fertilizer applications will run through October or November.
Below, we’ll walk you through a complete fertilizer schedule for your established Kentucky Bluegrass lawn to provide all the essential nutrients required to make your grass thrive. Our schedule removes the guesswork and math, making lawncare simple.
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How Do You Fertilize Kentucky Bluegrass?
Established Kentucky Bluegrass requires 3–6 pounds of nitrogen per 1,000 square feet annually. This drives optimal growth. In addition to nitrogen, your Bluegrass lawn also needs phosphorus and potassium for continued health, as well as iron for green color.
- Provide 3–6 pounds of Nitrogen per year.
- Do not provide more than 1.5 pounds of nitrogen at once, as this can cause fertilizer burn and damage grass.
- To follow our schedule, all you need to know is your lawn’s square footage. This can be determined using a tape measure.
Our schedule is calculated to provide the optimal amount of Nitrogen to your Kentucky Bluegrass without causing fertilizer burn. With this easy 4-stage fertilization schedule, your Bluegrass will stay green from spring until winter.
Apply a slow-release fertilizer in spring (March–April). Milorganite is our preferred source for early spring fertilizer. It contains slow-release nitrogen and iron that encourages blade growth and color. Spread it at a rate of 0.75 pounds of nitrogen per 1,000 square feet.
- Apply in spring, once your lawn has begun to green up (typically February—April).
- Milorganite is the perfect spring fertilizer. The nitrogen and phosphorus encourage blade and root growth.
- Milorganite contains iron for rich, green color.
- Apply 12 pounds of Milorganite per 1,000 square feet of lawn. This will deliver 0.75 pounds of Nitrogen per 1,000 square feet.
Bluegrass needs a good combination of nitrogen and phosphorus in spring. The nitrogen encourages faster green-up, but the phosphorus also drives root growth. Bluegrass spreads via rhizomes, underground roots. Encouraging root development helps your Bluegrass spread faster and builds a thicker yard. An extremely nitrogen-rich fertilizer in early spring will force blade growth and hinder crucial root development.
In May, apply a high-nitrogen fertilizer with potassium, to boost Kentucky Bluegrass. The potassium in the fertilizer is an essential nutrient that helps grass fight diseases and thrive through the drought and heat of peak summer months.
- Apply nitrogen fertilizer between May 1 and June 1.
- The fertilizer should have a high nitrogen content, as well as potassium to help grass resist disease and drought.
- Scotts Northern Lawn Food is a good high-nitrogen fertilizer for Kentucky Bluegrass.
- Apply 3 pounds of Scotts Northern Lawn Food per 1,000 square feet of lawn. This will provide 1 pound of nitrogen per 1,000 square feet.
This late spring application is crucial for Kentucky Bluegrass health. Essentially, this application of fertilizer will be responsible for keeping your grass green through the hottest part of summer. You will not want to fertilize your Bluegrass at the height of summer, as the combination of nitrogen and summer heat can dry out and damage Kentucky Bluegrass.
Wait until the summer peak has passed and apply fertilizer between September 1 and September 15. Kentucky Bluegrass actually experiences the most growth in late summer and fall, and it requires fuel at this time. Fall is also the time Bluegrass has a second increase in rhizome growth and spreads to heal damaged areas of the lawn, so be certain to provide phosphorus to help your lawn repair from summer stress.
- Spread fertilizer September 1–September 15
- Apply 20 pounds of Milorganite per 2,500 square feet of lawn. This will deliver 1.25 pounds of Nitrogen per 1,000 square feet.
- If you plan on overseeding your Kentucky Bluegrass lawn in the fall, use Scotts Turf Builder Starter Food at this time.
- When using Scotts Turf Builder Starter Food, apply 5 pounds per 1,000 square feet. This will provide 1.25 pounds of nitrogen per 1,000 square feet.
- It’s best to apply both Milorganite and Scotts Turf Builder for a hybrid fertilizer approach.
Remember, late summer is the best time to overseed your Kentucky Bluegrass lawn. If you plan on doing so, overseed and fertilize at the same time to take care of two jobs at once. Just make sure to use a starter fertilizer. Starter fertilizers have an extremely high phosphorus content needed to make your new seedlings develop roots.
It’s essential to give Kentucky Bluegrass an extra application of fertilizer in fall. This will be used for its final growth spurt and will allow the grass to store energy over winter. It results in a faster, stronger green-up the following spring.
- Make your final fertilizer application October 15–October 31.
- Apply 4 pounds of Scotts Northern Lawn Food per 1,000 square feet of lawn. This will provide 1.25 pounds of nitrogen per 1,000 square feet.
By using a high nitrogen fertilizer at this time, you’re essentially fueling your Kentucky Bluegrass through winter dormancy, so that it can come roaring to life in spring. Don’t skip this application.
How Do You Prevent Fertilizer Burn in Kentucky Bluegrass?
To keep your Kentucky Bluegrass safe from fertilizer burn, do not apply more than 1.5 pounds of fertilizer per 1,000 square feet in a single application. Nitrogen overload is the cause of fertilizer burn, as nitrogen-rich fertilizer absorbs water, drying out the soil and grass blades.
- Do not apply more than 1.5 pounds of nitrogen per 1,000 square feet in a single 6-week period.
- Avoid applying high-nitrogen fertilizer during peak summer heat (June—August).
- Too much fertilizer, including Milorganite, or fertilizer applied in hot temperatures, will pull moisture out of Kentucky Bluegrass, turning it brown and potentially killing it.
Kentucky Bluegrass is extremely susceptible to fertilizer burn. This is because it has relatively shallow roots. Because of this, it’s easy for too much fertilizer to dry out the soil around Bluegrass roots, burning the grass. If you see browning beginning to occur after fertilization, increase the amount of water you’re giving your lawn.
What is the Best Time to Fertilize Kentucky Bluegrass?
Kentucky Bluegrass needs 4 fertilizer applications per year to thrive. The schedule for annual Bluegrass fertilization is:
- March/April: Apply slow-release nitrogen fertilizer at 0.75 pounds of nitrogen per 1,000 square feet.
- May: Apply high nitrogen fertilizer at 1 pound of nitrogen per 1,000 square feet.
- September: Apply slow-release fertilizer at 1.25 pounds of nitrogen per 1,000 square feet. If you are overseeding in the fall, use a starter fertilizer instead.
- October: Apply high-nitrogen fertilizer at 1.25 pounds of nitrogen per 1,000 square feet.
Along with water and proper mowing practices, a good fertilizer schedule for Kentucky Bluegrass results in a green lawn from spring thaw until the winter freeze. Simply follow our easy schedule and watch your lawn flourish.