LawnWeather

Flagstaff, AZ Lawn Care Calendar

In a typical year, put down crabgrass preventer in Flagstaff between May 15 and Jun 8. Seed or sod warm-season grass between Jun 23 and Jul 19. The last spring frost usually comes around May 30. Most lawns here are warm-season grass (Bermuda, zoysia, St. Augustine, centipede).

Typical lawn care dates in Flagstaff

Crabgrass preventer (pre-emergent)
May 15 – Jun 8
Fertilizer
Jun 23 – Aug 21
Seeding, sodding & plugging
Jun 23 – Jul 19
Fall pre-emergent (winter weeds)
Jul 1 – Jul 22
Light band: typical frost-free season. Bars: typical windows.
TaskTypical window
Crabgrass preventer (pre-emergent)Crabgrass sprouts once soil stays above 55°F. Apply when soil reaches 50°F, before that happens.May 15 – Jun 8
FertilizerFeed after green-up once soil stays above 65°F; stop about 6 weeks before the first frost.Jun 23 – Aug 21
Seeding, sodding & pluggingWarm-season grass needs soil above 65°F and about 10 weeks to establish before frost.Jun 23 – Jul 19
Fall pre-emergent (winter weeds)Stops annual bluegrass (Poa annua) and winter weeds; apply as soil drops below 70°F.Jul 1 – Jul 22

Median dates, 2016–2025, from NOAA weather data for Flagstaff. This year's dates can differ by a few weeks.

Month-by-month lawn care in Flagstaff

  1. JanuaryNo treatments due; mow as needed.
  2. FebruaryNo treatments due; mow as needed.
  3. MarchNo treatments due; mow as needed.
  4. AprilNo treatments due; mow as needed.
  5. MayCrabgrass preventer (pre-emergent)
  6. JuneCrabgrass preventer (pre-emergent)FertilizerSeeding, sodding & plugging
  7. JulyFertilizerSeeding, sodding & pluggingFall pre-emergent (winter weeds)
  8. AugustFertilizer
  9. SeptemberNo treatments due; mow as needed.
  10. OctoberNo treatments due; mow as needed.
  11. NovemberNo treatments due; mow as needed.
  12. DecemberNo treatments due; mow as needed.

Soil temperature in Flagstaff by month

Average soil temperature 4 inches down, estimated from 2016–2025 weather. It bottoms out in January at 29°F and peaks in July at 67°F. Crabgrass preventer goes down when it reaches 50°F, usually around May 15.

JanFebMarAprMayJunJulAugSepOctNovDec
29°F32°F36°F43°F50°F61°F67°F66°F60°F49°F39°F33°F

Flagstaff lawn timing, year by year

Over the last 10 years, soil in Flagstaff reached 50°F, the signal for crabgrass preventer, as early as Apr 12 (2025) and as late as Jun 4 (2019): 53 days apart. A fixed calendar date can't follow that, which is why the report above uses this year's soil temperature. Between the typical last spring frost (May 30) and first fall frost (Oct 2), the growing season lasts about 125 days.

YearCrabgrass window openedLast spring frostFirst fall frost
2025Apr 12May 21Oct 5
2024May 15May 23Oct 16
2023May 15Jun 25Oct 3
2022May 15Jun 20Oct 13
2021May 6May 26Oct 1
2020Apr 27Jun 10Sep 9
2019Jun 4Jun 1Sep 22
2018Apr 27May 27Oct 7
2017May 24May 22Sep 24
2016May 31May 31Sep 16

Estimated from daily temperatures for Flagstaff. A dash means it didn't happen that year.

Frequently asked questions

When should I apply pre-emergent in Flagstaff?

In a typical year, between May 15 and Jun 8. Put it down when soil reaches 50°F, before it stays above 55°F and crabgrass starts sprouting. Early springs move this up by a week or more, so check this year's soil temperature above.

When is the best time to plant grass seed in Flagstaff?

Once soil stays above 65°F, typically Jun 23 – Jul 19, leaving about 10 weeks before the first frost.

When is the last frost in Flagstaff?

The median last spring frost is May 30 and the median first fall frost is Oct 2 (2016–2025).

How long is the growing season in Flagstaff?

About 125 days, from the median last spring frost on May 30 to the median first fall frost on Oct 2 (2016–2025).

Lawn care guides

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