There's so much more to a great yard than just mowing the lawn.

In Colorado, Should You Fertilize Your Lawn in March?

The short answer is maybe, maybe not. Out of all the recommended times to fertilize a lawn in Colorado, early spring is the one fertilization most lawns can do without. This is a little strange, considering that it’s the one time of year many of us think about fertilizing our lawns at all.

Greening Up Lawn

When coming out of dormancy in spring, it’s normal for a lawn to have a mix of straw-colored and green leaves.

Keep in mind that it’s normal for a lawn to have a mix of straw-colored and green leaves as it comes out of winter dormancy. That’s because you have the new green leaves growing up through the dead leaves of last year’s growth. So, it’s important to base your decision on other factors.


Here are seven questions to help you decide whether to fertilize now or wait until May.

1. Did you fertilize your lawn last fall?

  • Yes, I fertilized sometime between September and November.
  • No, I didn’t know that was a good time or I forgot to do it.

2. Do you normally leave the clippings on the lawn when you mow?

  • Yes, I leave the clippings on the lawn to decompose naturally.
  • No, I collect the grass clipping when I mow and dispose of them elsewhere.

3. Does your lawn hardly ever experience heavy use?

  • Yes, I never notice traffic wear on my lawn.
  • No, my lawn experiences a lot of use from people and/or pets and it shows up as traffic wear.

4. Is your lawn generally healthy, meaning thick, green and growing at a moderate rate?

  • Yes, it’s growing just fine.
  • No, it’s thin or not very vigorous.

5. Are you generally satisfied with the way your lawn looks?

  • Yes
  • No, I wish it looked better.

6. Does your lawn look like it’s greening up and growing pretty well already this spring?

  • Yes, it’s greening up and has grown a little bit this spring.
  • No, it’s not greening up that well and it doesn’t seem to be growing at all. (Note, it’s important to water a few times if you didn’t winter water before answering this question, to ensure the lawn has come out of winter dormancy.)

7. Has your lawn been in place for three years or more?

  • Yes, it’s been there for at least three years.
  • No, it was installed (either seeded or sodded) within the last three years.

Your Results

If you answered yes to most of the questions, skip the March-April fertilization. Wait until May 1-June 15 to fertilize. If you answered no to most of the questions, then go ahead and apply a light dose of fertilizer (about half the normal rate) between March 15 and April 15. Fertilize again between May 1 and June 15 at the regular rate.

Thick Lawn in Spring

This lawn is thick and green in spring, so it doesn’t need to be fertilized until May to early June.

Thin Lawn in Spring

This lawn is thin in spots and not growing vigorously. It could benefit from a light fertilization in mid-March to mid-April.

What’s wrong with fertilizing in early spring?

A few things. First, most lawns are busy forming roots at this time of year. If you fertilize too early, you stunt the root growth, which makes the grass more susceptible to browning in mid-summer. Second, it’s common for lawns that are over fertilized in spring to be more susceptible to lawn diseases. Third, you end up mowing twice per week if you over fertilize in spring. It’s best to wait until late spring to fertilize. However, if you lawn is starving for nutrients, it’s important to fertilize.

 When is the best time of year to fertilize your lawn in Colorado?

For most homeowners with Kentucky bluegrass lawns, the answer is three times per year.

  • Once around Mother’s Day, or May 1 to June 15.
  • Once around Labor Day, or August 15 to September 15.
  • Once around Halloween, or October 1 to November 1.

Fertilizing in the mid-March to April is needed only under the special circumstances described above.

What’s interesting is that for most people, it’s counter intuitive to think about fertilizing their lawn in fall, but it’s a really good idea. It’s actually more important to fertilize in the fall than in the spring. Learn more about it here. And trust me. I’ll be reminding you.

To learn more from a past post about which type of fertilizer I recommend, please click here.

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2 Responses to In Colorado, Should You Fertilize Your Lawn in March?

  1. Gary Kennedy March 9, 2017 at 1:05 pm #

    My lawn is generally in good shape throughout the growing season as I water as suggested, fertilize three times a year, and aerate twice a year. However, living in the east part of Aurora, Colorado makes maintaining a lawn somewhat of a “challenge”. My question today is, since the weather is quite warm and very dry, should I begin to water the grass this early? The new blades are starting to grow through the winter blades. Is the lawn still too dormant to water this soon? Thanks for your suggestions.

    • Catherine March 9, 2017 at 7:52 pm #

      Hi Gary, glad to hear that your lawn care techniques are working. Sounds like you’re right on track. Yes, I would go ahead and water. I’ve watered my home landscape twice already. The soil temperatures have ranged from 40-60 degrees recently, which means the roots of turfgrass are starting to grow. They start to become active when the soil warms over 40 degrees. That’s why you’re seeing the new grass blades emerging. It’s been unusually dry and warm. Sometimes if we get a cool, moist spring we can start to water later. We just didn’t win the lottery this year. The only time I don’t winter water lawns is if the daytime temperatures have been well below 40 degrees for an extended period, the soil is frozen, or there is ice or snow on the grass. Otherwise, I try to winter water at least once per month from Nov-Feb, twice in March, and once per week in April. Hope that helps. Let me know how things turn out!

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