Want green, healthy turf in the spring? Then you must fertilize correctly in the fall!

Fall fertilization of turfgrass is extremely important, especially for cool season turfgrasses like Tall Fescue, Kentucky Bluegrass, and Perennial Rye. If you've been neglecting some of your lawns this summer, now is the time to get them back in shape!

This cheat sheet covers the role of fall fertilizer in programs for both warm season grasses and cool season grasses and when overseeding for winter. We'll also look at recommended fertilizer formulations separated by region.

Fertilizing Warm Season Grasses

Common species: Bermuda grass, Zoysia grass, and St. Augustine grass.

Where they grow: Southern U.S., e.g. Florida, Arizona, southern Texas, and southern California.

Seasonal growth pattern: These grasses grow actively starting in spring and through the summer. In most cases, they go completely dormant in winter unless they're overseeded with a cool season grass.

Fertilizing in fall: With warm season turf, it’s important to stick with fertilizing in the spring and summer, tapering off in fall.

These grasses often go dormant in the winter. So when warm season grasses are fertilized with applications of quick release nitrogen too late into the fall, their tissues are likely to become tender rather than harden off in preparation for the colder temperatures. This can result in damage to the turf and a poor spring recovery out of dormancy.

However a properly timed application of slow release nitrogen plus high potassium can aid in carbohydrate storage for the winter and increase turf density, meaning better spring recovery and defense against weed infestation.

Fertilizing Cool Season Grasses

Common species: Kentucky Bluegrass, Perennial Ryegrass, Bent Grass, Tall Fescue.

Where they grow: In true seasonal climates and coastal, temperate regions.

Seasonal growth pattern: These grasses grow most actively in the spring and in the fall. In true seasonal climates, particularly those that receive snow, these grasses go dormant during the winter. In a lot of coastal, more temperate regions, they will still grow through the winter, but typically a lot slower than in the spring and in the fall.

Fertilizing in fall: For cool season grasses, the fall fertilization is the most critical. If you only have one time you COULD fertilize each year, THIS should be it. A proper “Winterizer” containing slow release nitrogen aids in carbohydrate storage, resulting in a strong root system that is less susceptible to winter damage.

If the turf is still actively growing when winter comes, it’s ok to continue fertilizing, but it’s not really that important to overall turf health. It’s more about keeping the turf green and your customer happy.

Fertilization Timing When Overseeding

When overseeding warm season grasses like Bermuda with a different cool season turf (usually Perennial Ryegrass) to maintain color during the winter, it can be a challenge to time the fertilization both in fall and the following spring.

You need to get the Ryegrass down in early fall and the last thing you want is the Bermuda to continue growing as you're establishing the Ryegrass. At the same time, any new seed that you put down to keep your turf green through the winter months is going to need starter fertilizer to promote root growth and establishment. To successfully transition from one growing season to the other, the taper down period of the Bermuda is a period you’ll want to avoid fertilizing. Let that really die down so that your Ryegrass can come in with success.

Then once the spring comes around, it’s very hard for the Bermuda to start its upswing if the Ryegrass is still actively growing. You'll want to avoid fertilizing in that late spring window so the Ryegrass can slow down.

In the end, properly timing fertilization when overseeding isn’t just about the right times to fertilize, but also knowing the right times to avoid fertilizing.

Recommended Fall Fertilizer Formulations by Region

Arizona & Nevada

TurfGro 6-20-20 ProStarter

• Contains high phosphorus, which is essential for root growth and strong development of the plant, and low nitrogen to prevent burning new seedlings.
• Phosphorus naturally existing in the soil is immobile and unreachable by small roots, so a high-phosphorus fertilizer should always be applied at or shortly after planting.

TurfGro 21-0-7 Cool Season

• Maintain turf vigor throughout the cold months with this high nitrogen fertilizer, of which 10% is nitrate nitrogen for quick green-up.
• Compare to Turf Royale – same Nitrogen content but also with non-staining Iron for dark green color!

California

TurfGro 21-2-15 Winterizer

• 50% slow release nitrogen (from XCU and XRT) provides turf with sustained feeding from fall into winter.
• High potassium strengthens plant structure and builds winter stress resistance.
• Wolf Trax Iron provides immediate and residual feeding, with little to no stain potential.

TurfGro 6-20-10 ProStarter

• Contains high phosphorus, which is essential for root growth and strong development of the plant, and low nitrogen to prevent burning new seedlings.
• Phosphorus naturally existing in the soil is immobile and unreachable by small roots, so a high-phosphorus fertilizer should always be applied at or shortly after planting.

 Colorado

TurfGro 21-2-15 Winterizer

• 50% slow release nitrogen (from XCU and Nutralene) provides turf with sustained feeding from fall into winter.
• High potassium strengthens plant structure and builds winter stress resistance.
• Non-staining iron provides deep green color.

TurfGro 15-15-15 Plant Pro

• A balanced fertilizer appropriate for seeding applications.
• Phosphorus naturally existing in the soil is immobile and unreachable by small roots, so a high-phosphorus fertilizer should always be applied at or shortly after planting.

Florida

TurfGro 16-0-8 Florida Turf

• The university recommended analysis for Florida lawns
• 50% slowly available Nitrogen from XCU polymer-coated-sulfur-coated urea provides uniform growth and sustained feeding
• Phosphorus-free formulation poses a lower risk of nutrient runoff to water sources and does not encourage weed germination
• High iron for additional quick color without flush growth

TurfGro 24-0-11 Florida Premium Turf

• 50% slow release Nitrogen from XCU polymer-coated-sulfur-coated urea provides uniform growth and sustained feeding
• Controlled release Nitrogen reduces the number of applications required, lowering labor and product costs
• Phosphorus-free formulation poses a lower risk of nutrient runoff to water sources and does not encourage weed germination

TurfGro 8-2-12 Premium Palm

• Specialty fertilizer formulated with a complete minors package to meet the needs of palms and other tropical plants
• Contains Kieserite – A controlled-release Magnesium source, which is university recommended to treat Magnesium deficiencies common in palms
• Nitrogen, Phosphorus and Potassium sources are polymer-coated, ensuring sustained feeding and low burn potential

 Idaho & Eastern Washington

TurfGro 21-0-15 Winterizer

• 50% slow release nitrogen (from XCU and XRT)vprovides turf with sustained feeding from fall into winter.
• High potassium strengthens plant structure and builds winter stress resistance.
• Wolf Trax Iron provides immediate and residual feeding, with little to no stain potential.
• Phosphorus-free formulation meets WA regulation and does not encourage winter weed establishment.

TurfGro 12-8-6 Starter

• 50% organic-based starter fertilizer, with 2.5% of the nitrogen from organic sources.
• Ideal formula to promote proper development of new lawns and seedlings in overseed applications

Texas

TurfGro 22-8-15 Winterizer

• 63% slow release Nitrogen from XCU polymer-sulfur-coated urea provides sustained feeding from fall through winter, with emphasis on root—not shoot—development
• High potassium strengthens plant structure and builds winter stress resistance

TurfGro 5-5-20 Winterizer

• A low Nitrogen, high Potassium fertilizer best suited for fall application to St. Augustine lawns.

TurfGro 15-15-15 Plant Pro

• A balanced fertilizer appropriate for seeding applications.
• Phosphorus naturally existing in the soil is immobile and unreachable by small roots, so a high-phosphorus fertilizer should always be applied at or shortly after planting.