# Lawn care calendar for Arizona: when to fertilize and seed > Arizona lawn calendar for the low desert: University of Arizona timing for bermudagrass, October ryegrass overseeding, fertilizer rates and NOAA frost dates. Canonical: https://lucernel.com/guides/lawn-care-calendar/arizona Last updated: 2026-10-17 Arizona lawn care in the low desert runs on a different clock from the rest of the country. Bermudagrass grows from spring to fall, goes blonde in winter, and is often overseeded with ryegrass in October so the lawn stays green. The University of Arizona's guides for Phoenix, Tucson and Yuma set the dates. **Overseed bermudagrass with ryegrass in October, and feed it half a pound of nitrogen a month while it grows.** University of Arizona turf specialist Kai Umeda sets overseeding at October 10 to November 10 in Phoenix, Casa Grande and Yuma, and September 25 to October 5 in higher-elevation Tucson, at 12 to 15 pounds of ryegrass seed per 1,000 square feet. Bermudagrass is the best-adapted lawn grass in the low desert and is planted in summer. Fertilize with 0.5 pound of nitrogen per 1,000 square feet once a month during the growing season, starting when soil holds 60 F in April. (University of Arizona Cooperative Extension) | Month | Bermudagrass left to go dormant | Bermudagrass overseeded with ryegrass | | --- | --- | --- | | January | Blonde and dormant; water once a month if there is no rain | Green ryegrass; mow and water by weather | | February | Starts to green as air warms; soil still too cool | Ryegrass lawn; water by weather | | March | Greening continues; wait for 60 F soil before feeding | Ryegrass lawn; water by weather | | April | Soil holds 60 F: light fertilizing and watering begin | Begin spring transition: mow lower, feed lightly | | May | Vigorous growth starts in the heat | Heat thins the ryegrass | | June | Water deep every three days; mow weekly | Finish transition back to bermudagrass; aerify from late June | | July | Feed 0.5 lb N monthly; aerify or dethatch | Feed 0.5 lb N monthly; aerify | | August | Feed 0.5 lb N monthly; plant sod or sprigs in summer | Feed 0.5 lb N monthly; aerify | | September | Feed 0.5 lb N monthly while it grows | Stop nitrogen 30 days before overseeding; higher Tucson seeds from September 25 | | October | Growth slows; frost can turn it blonde in November or December | Overseed with ryegrass; Phoenix window opens October 10 | | November | Blonde after several frosty nights | Overseeding window to November 10; feed 2 weeks after emergence | | December | Dormant | Ryegrass lawn | The source guide covers the low elevation desert around Phoenix, Tucson, Casa Grande and Yuma; northern Arizona lawns run on a cool-season calendar not covered here. ## Which grasses grow where in Arizona In the low desert, bermudagrass is the best-adapted lawn grass for heat and water use. Common bermudagrass can be seeded or planted as sod, plugs or sprigs. Hybrid bermudagrasses are sterile, so they have to be planted vegetatively. Both grow hard in summer and go dormant in winter, and several frosty nights in November or December turn them blonde. Zoysiagrass and St. Augustinegrass also go dormant in winter, but the University of Arizona says they generally are not suited to overseeding. The ryegrasses (perennial, annual and the intermediate hybrid) are the usual winter lawn. ## Frost dates from NOAA Dates are the NOAA 1991-2020 normals for the last spring and first fall 32 F freeze at 50% probability. Tucson International Airport averages February 5 and December 9, about 307 days apart by our count. Flagstaff Pulliam Airport averages June 4 and September 28, about 116 days apart. Phoenix Sky Harbor lists January 5 and January 3, two days apart in the same cold week. There is no frost-free season to count in Phoenix. The University of Arizona ties winter color loss to several frosty nights in November or December instead. ## Spring Non-overseeded bermudagrass starts greening in February when the air warms, but soil is not ready. When soil temperature is consistently 60 F, usually in April, growth picks up and light fertilizing and watering can begin. Hot, dry May and June weather starts the strongest growth. On an overseeded lawn, the spring job is to hand the grass back to the bermudagrass. Lower the mowing height by 35 percent, mow more often, apply 0.25 pound of nitrogen weekly, keep watering, and once 80 percent of the lawn is bermudagrass, verticut lightly and fertilize at 0.25 to 0.5 pound with a week of drier soil to stress the ryegrass. ## Summer Summer is the time to plant a new bermudagrass lawn. Seed needs about a month and multiple waterings a day; sod gives a usable lawn in a week; sprigs fall in between. A new lawn should not be overseeded its first winter. After that, mow at least weekly, fertilize with half a pound of nitrogen per 1,000 square feet each month, and water deep every three days instead of daily. Use a higher-phosphate fertilizer the month you seed or sod. Aerify or dethatch in summer when the grass is actively growing. Bermudagrass needs about 100 days of active growth to build roots and rhizomes before it can be overseeded. ## Fall October is the ideal overseeding month, when daytime highs are 80 to 85 F and nights are near 55 F. Seeding too early favors the bermudagrass, and too late risks frost on the seedlings. In the weeks before: stop nitrogen on the bermudagrass 30 days ahead, raise the mowing height 30 to 40 percent and cut irrigation 30 percent two weeks ahead, then mow back down and lower the cut another 25 to 30 percent just before seeding, and leave the clippings. On the day, spread 12 to 15 pounds of ryegrass per 1,000 square feet in two directions and rake it in. Water three to four times a day for 7 to 10 days, then taper to about weekly, and fertilize two weeks after emergence with 16-20-0 at 5 pounds per 1,000 square feet, watering it in. First mowing is when ryegrass reaches 2.75 to 3 inches. ## Winter An overseeded lawn needs far less water than the bermudagrass did in summer, with amounts driven by soil type, temperature and rain. The university points to AZMET, the Arizona weather network, for a daily watering guide. A dormant lawn that was not overseeded generally needs no extra water, unless winter rains are missing, in which case run the system about once a month from December through February. The lawn fertilizer calculator on this site is handy for turning the 0.5 pound monthly target into pounds of a particular bag. ## Frequently asked questions ### When should I overseed my lawn in Arizona? October is ideal. The University of Arizona gives October 10 to November 10 for Phoenix, Casa Grande and Yuma, and September 25 to October 5 for higher-elevation Tucson. ### What grass grows best in the Arizona low desert? Bermudagrass is the best-adapted lawn grass for the heat and water use of the low desert. Zoysia and St. Augustinegrass also grow there but are generally not overseeded. ### How much should I fertilize bermudagrass in Arizona? Half a pound of nitrogen per 1,000 square feet once a month during the growing season, per the University of Arizona's maintenance table. ### How much seed do I need to overseed with ryegrass? 12 to 15 pounds of ryegrass per 1,000 square feet, spread half in each direction. ### Can Lawnzo help me follow a Arizona lawn schedule? Lawnzo for iPhone turns a calendar like this one into a plan for each lawn you keep, using your grass type, sun and irrigation. Each job is checked against the weather forecast, and the app tells you the reason when it moves one. You can log products and photos in the journal. ## Sources (checked 2026-10-02) - [University of Arizona Cooperative Extension, az1817: A Turfgrass Maintenance Guide for Residential and Commercial Lawns in the Low Elevation Arizona Desert](https://extension.arizona.edu/publication/turfgrass-maintenance-guide-residential-and-commercial-lawns-low-elevation-arizona) - [University of Arizona Cooperative Extension, az1683: Overseeding Winter Grasses into Bermudagrass Turf](https://extension.arizona.edu/publication/overseeding-winter-grasses-bermudagrass-turf) - [NOAA NCEI 1991-2020 normals: frost dates for Phoenix Sky Harbor International Airport, Tucson International Airport, Flagstaff Pulliam Airport (API query)](https://www.ncei.noaa.gov/access/services/data/v1?dataset=normals-annualseasonal-1991-2020&stations=USW00023183,USW00023160,USW00003103&dataTypes=ANN-TMIN-PRBLST-T32FP50,ANN-TMIN-PRBFST-T32FP50&format=json) - [NOAA NCEI, U.S. Climate Normals 1991-2020 (product page)](https://www.ncei.noaa.gov/products/land-based-station/us-climate-normals) - [NOAA NCEI, station inventory (GHCN-Daily station list)](https://www.ncei.noaa.gov/pub/data/ghcn/daily/ghcnd-stations.txt)