When to Fertilize Your Lawn in Colorado

one man farmer is fertilizing the lawn soil. male hand of worker, Fertilizer For Lawns in springtime for the perfect lawn. Organic lawn fertilizer in man's hand on garden

Knowing when to fertilize your lawn in Colorado hinges on whether you have warm-season or cool-season grass, with spring through summer or fall being the ideal times. 

In this article, we’ll tell you everything you need to know about when to fertilize your lawn to keep it looking lush and vibrant in the Centennial State.

Best time to fertilize your lawn in Colorado

The type of grass in your Colorado lawn will influence your fertilizing schedule. For cool-season grasses, the best time to fertilize is in the fall. For warm-season grasses, it’s late spring through summer.

Fertilizing your lawn is not just about maintaining its lush appearance. It’s also important for bolstering your grass against diseases and environmental stressors, such as drought conditions. 

To ensure that you’re not applying fertilizer blindly but nourishing your lawn with what it truly needs, consider conducting a soil test first. It will pinpoint any nutrient deficiencies and guide your schedule, giving information on whether your lawn would benefit more from a single annual treatment or needs more applications to look its best.

Let’s dive into the specifics of this:

Fertilizing cool-season grasses in Colorado

growth of cool season grass
Infographic by Juan Rodriguez

Cool-season grasses like Kentucky bluegrass, tall fescue, and perennial ryegrass are the most common grasses in Colorado. In fall, they’re in their peak growth phase, which makes this season perfect for fertilizer application.

Here are a few tips regarding fertilizing in the fall:

  • Single annual treatment: If a soil test indicates only one fertilizer application is needed annually, or if you choose to fertilize just once, schedule this in the fall.
  • Timing by altitude: Fertilize from late September to early November if you live in lower altitudes. However, if you live in higher altitudes like Colorado Springs, apply fertilizer from mid-August to early September to ensure nutrients are absorbed before the ground freezes. Either way, make sure to fertilize two to three weeks before the ground begins to freeze.
  • Spring fertilization: If you applied fertilizer in late fall, it might not be necessary to fertilize again in early spring. You can wait until late spring to early summer (May to mid-June).
  • Special considerations for sandy soils: Avoid fertilizing after late September if your soil is sandy, like along the Eastern Plains or in South Denver, as there is a risk of nutrients leaching into groundwater.
  • Pro tip: Do not fertilize warm-season grasses during fall.

Fertilizing warm-season grasses in Colorado

growth of warm season grass
Infographic by Juan Rodriguez

Native warm-season grasses like buffalograss and blue grama behave differently than their cool-season counterparts, with peak growth occurring during the warmer months. Here are the key guidelines for fertilizing warm-season grass types in Colorado:

  • Best fertilization period: The best time to fertilize warm-season grasses is from late spring through summer, or May to August. 
  • Timing for application: Only fertilize after the grass has fully greened up. Starting too early can prompt the grass to prioritize leaf blade growth instead of developing a robust root system.
  • Frequency: Warm-season grasses in Colorado should only be fertilized up to two times a year.
  • Pro tip: Do not fertilize cool-season grasses during summer. Make sure you know which type of grass you have.

Colorado lawn fertilizer schedule

a man spreading fertilizer
Adobe Stock

To help you navigate the nuances of lawn care in Colorado, the table below provides a detailed schedule for fertilizing your lawn, whether it’s composed of cool-season or warm-season grasses.

Grass typeFertilization periodDetails
Cool-season grassesFall (primary)• Late September to early November for lower altitudes
• Mid-August to early September for higher altitudes
Spring (secondary)• March to mid-June, as grass begins to grow
• May to mid-June if you also fertilized in fall
Warm-season grassesLate spring to summer (only)• May to August, after grass has greened up

How often to fertilize your lawn in Colorado

The frequency of lawn fertilization in Colorado varies widely and is not a one-size-fits-all answer. Depending on your specific lawn needs and conditions, fertilization can range from one to four times a year.

Here are some general guidelines based on grass type and recommendations from Colorado State University:

Cool-season grasses

  • First application: 1/2 to 1 pound of nitrogen per 1,000 square feet in early spring.
  • Second application: 1 pound of nitrogen per 1,000 square feet in late spring.
  • Third application: 1 pound of nitrogen per 1,000 square feet in early fall.
  • Fourth application (optional): 1 pound of nitrogen per 1,000 square feet in late fall.

However, that doesn’t mean you’ll have to fertilize your lawn four times a year. A soil test will give a more accurate recommendation, but in general, fall applications are the most beneficial. In addition, if you fertilized in late fall, it might not be necessary to fertilize in early spring.

Warm-season grasses

  • First application: 1/2 to 1 pound of nitrogen per 1,000 square feet in late spring.
  • Second application: 1/2 to 1 pound of nitrogen per 1,000 square feet in July to August.

For all grass types, leaving grass clippings after mowing can naturally reduce nitrogen needs by about 1/4 to 1/3, as they decompose and return nutrients to the soil. 

How to choose a fertilizer for your Colorado lawn

Hand in glove holding nitrogen fertilizer
Adobe Stock

Choosing the right fertilizer for your Colorado lawn involves understanding the various types available and selecting the one that best suits your lawn’s specific needs. Here are some considerations when picking a fertilizer:

  • Nutrient composition: Base your choice primarily on the results of a soil test. This will tell you exactly which nutrients your lawn is lacking and which it has in abundance. Most Colorado lawns, for instance, usually need more nitrogen and less (or no) phosphorus and potassium.
  • Convenience: Decide whether you prefer the ease of applying liquid fertilizers or if you’re fine with using granular types, which are usually more cost-effective and have longer-lasting effects. Some products also include weed control (the so-called “weed and feed”), which might be beneficial if you’re dealing with an infestation.
  • Price: Fertilizers come in a wide range of prices, and the best choice often balances cost with effectiveness. Consider how much you’re willing to spend.

Pro tip: Colorado State University recommends using slow-release fertilizers. These types of fertilizers provide a supply of nutrients over time, reducing the risk of leaching losses and ensuring your grass is continuously nourished throughout the season.

Best fertilizers for Colorado lawns

Different active ingredients of a fertilizer in the soil
Adobe Stock

We have compiled a list of the best lawn fertilizers for Colorado. Each product has been selected based on its high nitrogen content while containing less than 5% of phosphorus and/or potassium, in line with most of Colorado’s soil needs. 

The N-P-K ratio is listed in parentheses. Products marked with an asterisk (*) include slow-release formulas.

Attention: Pennington UltraGreen might be one of the best weed and feed products for Colorado, but Colorado State University does not recommend using weed and feed products. Herbicides and fertilizers often need to be applied at different times for optimal effectiveness. To better understand the appropriate timing for weed control, refer to our Colorado Lawn Care Schedule.

FAQ

When should I weed and feed my lawn in Colorado?

Most weed and feed products are designed for early spring application. It’s important not to apply these products during summer or when rain is expected within 24-hours post application.

Weed and feed products should ideally be used only if there is a widespread weed problem to avoid excessive use of herbicides when there is no need. Consider spot-treating with post-emergent herbicides instead of applying weed and feed.

What is the best lawn fertilizer for Denver?

When selecting a fertilizer for your Denver lawn, prioritize products with a higher ratio of nitrogen, as indicated by the first number in the NPK (Nitrogen-Phosphorus-Potassium) series on fertilizer labels. Since Colorado lawns typically have sufficient phosphorus and potassium, these nutrients are needed in lower quantities.

For residents of South Denver, where the soil can be sandy, slow-release fertilizers are advisable. Options such as sulfur-coated or natural, organic fertilizers can reduce the risk of leaching.

If you’d rather leave this decision to a professional, consider hiring a Denver lawn care pro.

When do I fertilize my lawn in Colorado Springs?

Due to its high altitude (over 6,000 feet), Colorado Springs lawns experience an early onset of winter compared to lower-altitude regions. As such, aim to apply fertilizer from mid-August to early September as soon as the weather begins to cool.

You can also apply fertilizer in the spring, as the snow melts and the soil begins to warm up, to help kickstart your lawn’s growth after winter. If you’re not sure about when to do it, you can leave it to a Colorado Springs lawn care pro near you.

Call a professional

Whether you’re battling early frosts in Colorado Springs, navigating the dry summers of Denver, or maintaining lush grass in the Rockies, caring for your Colorado lawn doesn’t have to be a solo effort. Call a lawn care professional near you. They can recommend the best products for your soil and handle the fertilizer application.

Lawn Love participates in the Amazon Services LLC Associates Program and other retailer affiliate programs. Lawn Love may earn revenue from products promoted in this article.

Main Image Credit: Adobe Stock

Maria Isabela Reis

Maria Isabela Reis is a writer, psychologist, and plant enthusiast. She is currently doing a PhD in Social Psychology; and can't help but play with every dog she sees walking down the street.