Kentucky Bluegrass responds well to fertilizer and will darken in color and look much healthier quickly. Without fertilizer, your lawn will become light green, thin, and will be easily invaded by weeds.
Don’t get carried away, though, and apply excessive fertilizer. Excessive fertilizer will not result in an excessively dark green lawn; rather, it will only cause your lawn to grow faster and thus need more frequent mowing. The most efficient way to fertilize is to use the dry, granular fertilizers.
Fertilizer recommendations:
1.) 4 lbs. of actual nitrogen per 1000 square feet per year
2.) Apply 1.5 lbs of actual nitrogen per 1000 square feet in mid-spring and early fall.
3.) Apply 1 lb of actual nitrogen in late winter.
4.) Use slow-release fertilizers in mid-spring and early fall.
5.) Water approximately 1 inch after fertilizing
It is important to use slow-release fertilizers when possible. Most major brands of lawn fertilizer will have a combination of soluble and slow-release forms of nitrogen (indicated on the label). Soluble nitrogen is available to the grass plant immediately while slow release nitrogen becomes available over the course of two to three months. In most situations it is best to have as much nitrogen in slow-release form as possible. Good brands of fertilizer will have 40-50% of the nitrogen in slow release form. This is usually noted in a statement like “containing 10% nitrogen in slow-release form.”
It is important to use slow-release fertilizer in the spring and fall. Avoid hose-end fertilizer sprays or dry fertilizers in which all of the nitrogen is in a soluble, quick-release form. However, the late winter fertilizer application should contain a soluble, quick-release form of nitrogen.
Unfortunately, most brands of fertilizer do not tell you how many actual pounds of nitrogen are in the bag. It is easy enough to calculate, though, using two simple pieces of information: the N-P-K ratio and the weight of the bag. Multiply the percentage of nitrogen (the first number in the N-P-K ratio) by the weight of the bag and divide by 100. For instance, a 50-pound bag of 12-4-8 fertilizer has 6 pounds of actual nitrogen (12% of 50).
Determine the amount of coverage by dividing the amount of actual nitrogen in the bag by the amount of nitrogen you want to apply in a single application. With Kentucky Bluegrass, you want to apply 1.5 pounds of actual nitrogen per 1000 square feet. Therefore, a bag that contains 6 pounds of actual nitrogen will cover 4000 square feet (6 divided by 1.5 pounds per 1000 square feet). If your lawn is less than 4000 square feet, remove the amount you do not need. Two cups of granular fertilizer weigh about 1 pound. All this calculating is a hassle, we recommend simply using an online calculator like the one found on our website.
When it comes to fertilizer, timing is everything. The following schedule will help you maintain a consistent level of nutrients in the soil.
Late Winter: Fertilize Kentucky Bluegrass lawns in late winter when soil temperatures rise to a consistent 50° in order to stimulate deep root growth. This is usually in late February/early March. Use high-nitrogen, low-phosphorus fertilizer like 18-0-4 that includes a pre-emergence weed control (unless you plan on reseeding in the spring). It is best if the nitrogen is NOT in slow-release form. Apply at the rate of 1 pound of actual nitrogen per 1000 square feet.
Mid-spring: Fertilize again 4-6 weeks later. This is usually around April 1st. Use a complete lawn fertilizer like 12-4-8 that contains a slow release form of nitrogen. Apply at a rate of 1.5 pounds of actual nitrogen per 1000 square feet.
Summer (optional): It is best not to fertilize Kentucky Bluegrass lawns during the summer months. If your Kentucky Bluegrass lawn is light green, or yellow, however, it may it useful to fertilize lightly. Apply no more than .5 pounds of actual nitrogen per 1000 square feet.
Early Fall: Fertilize your Kentucky Bluegrass lawn again in early September. You can use the same complete fertilizer you have been using, or switch to a fertilizer with little or no phosphorus, but a higher rate of potassium. This might be something like 12-4-14 or 12-0-12. Either way, make sure the fertilizer contains a slow-release form of nitrogen and apply at the rate of 1.5 pounds of actual nitrogen per 1000 square feet. There is no need to ‘winterize’ your lawn by applying a late fall application of special fertilizer. Save your time and energy.
Winter: There is often the temptation to fertilize a Kentucky Bluegrass lawn during the mild Southern winters. It is important to remember, however, that grass roots do not absorb nutrients when the soil temperatures are below approximately 45°. While a warm spell seems the perfect time to fertilize an off-color Kentucky Bluegrass lawn, soil temperatures will rarely reach the minimal level for root activity.
Don’t get carried away, though, and apply excessive fertilizer. Excessive fertilizer will not result in an excessively dark green lawn; rather, it will only cause your lawn to grow faster and thus need more frequent mowing. The most efficient way to fertilize is to use the dry, granular fertilizers.
Fertilizer recommendations:
1.) 4 lbs. of actual nitrogen per 1000 square feet per year
2.) Apply 1.5 lbs of actual nitrogen per 1000 square feet in mid-spring and early fall.
3.) Apply 1 lb of actual nitrogen in late winter.
4.) Use slow-release fertilizers in mid-spring and early fall.
5.) Water approximately 1 inch after fertilizing
Type of Fertilizer to use on Bluegrass
Fertilizers are categorized by the percentages of nitrogen (N), phosphorus (P), and potassium (K) contained in the bag. All fertilizer bags are clearly labeled with these three numbers commonly referred to as the N-P-K ratio. For Kentucky Bluegrass, it is best to use a slow-release formula with a 3-1-2 ratio. An example would be a 12-4-8 fertilizer.It is important to use slow-release fertilizers when possible. Most major brands of lawn fertilizer will have a combination of soluble and slow-release forms of nitrogen (indicated on the label). Soluble nitrogen is available to the grass plant immediately while slow release nitrogen becomes available over the course of two to three months. In most situations it is best to have as much nitrogen in slow-release form as possible. Good brands of fertilizer will have 40-50% of the nitrogen in slow release form. This is usually noted in a statement like “containing 10% nitrogen in slow-release form.”
It is important to use slow-release fertilizer in the spring and fall. Avoid hose-end fertilizer sprays or dry fertilizers in which all of the nitrogen is in a soluble, quick-release form. However, the late winter fertilizer application should contain a soluble, quick-release form of nitrogen.
How much fertilizer to apply
Most bags of fertilizer are covered from top to bottom with completely useless information that is written by the fertilizer company’s marketing department. Usually, a vague and only nominally helpful phrase like, “fertilizes up to 10,000 square feet,” is the only semblance of instruction. Luckily there is an easy way to determine how much fertilizer to apply. The first step is to figure out how much actual nitrogen is contained in the bag. Kentucky Bluegrass lawns grow best with 3-5 pounds of actual nitrogen per 1000 square feet each year (distributed in three applications), regardless of the brand or N-P-K ratio. Apply 1 pound of actual nitrogen per 1000 square feet in late winter. Then, switch to a fertilizer with slow-release nitrogen and apply 1.5 pounds of actual nitrogen per 1000 square feet in mid-spring and again in early fall.Unfortunately, most brands of fertilizer do not tell you how many actual pounds of nitrogen are in the bag. It is easy enough to calculate, though, using two simple pieces of information: the N-P-K ratio and the weight of the bag. Multiply the percentage of nitrogen (the first number in the N-P-K ratio) by the weight of the bag and divide by 100. For instance, a 50-pound bag of 12-4-8 fertilizer has 6 pounds of actual nitrogen (12% of 50).
Determine the amount of coverage by dividing the amount of actual nitrogen in the bag by the amount of nitrogen you want to apply in a single application. With Kentucky Bluegrass, you want to apply 1.5 pounds of actual nitrogen per 1000 square feet. Therefore, a bag that contains 6 pounds of actual nitrogen will cover 4000 square feet (6 divided by 1.5 pounds per 1000 square feet). If your lawn is less than 4000 square feet, remove the amount you do not need. Two cups of granular fertilizer weigh about 1 pound. All this calculating is a hassle, we recommend simply using an online calculator like the one found on our website.
When to spread Fertilizer:
When it comes to fertilizer, timing is everything. The following schedule will help you maintain a consistent level of nutrients in the soil.
Late Winter: Fertilize Kentucky Bluegrass lawns in late winter when soil temperatures rise to a consistent 50° in order to stimulate deep root growth. This is usually in late February/early March. Use high-nitrogen, low-phosphorus fertilizer like 18-0-4 that includes a pre-emergence weed control (unless you plan on reseeding in the spring). It is best if the nitrogen is NOT in slow-release form. Apply at the rate of 1 pound of actual nitrogen per 1000 square feet.
Mid-spring: Fertilize again 4-6 weeks later. This is usually around April 1st. Use a complete lawn fertilizer like 12-4-8 that contains a slow release form of nitrogen. Apply at a rate of 1.5 pounds of actual nitrogen per 1000 square feet.
Summer (optional): It is best not to fertilize Kentucky Bluegrass lawns during the summer months. If your Kentucky Bluegrass lawn is light green, or yellow, however, it may it useful to fertilize lightly. Apply no more than .5 pounds of actual nitrogen per 1000 square feet.
Early Fall: Fertilize your Kentucky Bluegrass lawn again in early September. You can use the same complete fertilizer you have been using, or switch to a fertilizer with little or no phosphorus, but a higher rate of potassium. This might be something like 12-4-14 or 12-0-12. Either way, make sure the fertilizer contains a slow-release form of nitrogen and apply at the rate of 1.5 pounds of actual nitrogen per 1000 square feet. There is no need to ‘winterize’ your lawn by applying a late fall application of special fertilizer. Save your time and energy.
Winter: There is often the temptation to fertilize a Kentucky Bluegrass lawn during the mild Southern winters. It is important to remember, however, that grass roots do not absorb nutrients when the soil temperatures are below approximately 45°. While a warm spell seems the perfect time to fertilize an off-color Kentucky Bluegrass lawn, soil temperatures will rarely reach the minimal level for root activity.
