In the low desert, the best window to overseed a Bermuda lawn with winter ryegrass is mid-October through November, once nights cool to about 55°F and days sit in the low 80s. Early November still works in Surprise and Sun City West if you start soon. Plan on light watering three or four times a day until the seed sprouts. If you'd rather save water, time and money, letting your Bermuda go dormant and tan for the winter is a perfectly healthy choice.
Why people overseed, and why the window is open now
Bermudagrass is the most common lawn in the West Valley because it handles our summers so well. Once nights turn cool, it slows down, goes dormant and turns a straw-tan color until spring. Overseeding means spreading a cool-season grass, usually perennial ryegrass, over the Bermuda in fall so the lawn stays green through the winter.
A green lawn looks nice when family visits for the holidays, and it gives grandkids and pets a softer place to play. It also takes work and a lot of water, especially in the first few weeks. Many Valley cities and water groups now encourage homeowners to skip it, and plenty of HOAs in Surprise allow a tan winter lawn. Before you buy seed, decide which option fits your yard, your schedule and your water bill.
University of Arizona turf experts point to October and November as the overseeding window for the low desert, ideally when daytime highs are around 80 to 85°F and nighttime lows are about 55°F. Timing matters in both directions:
- Too early: while it's still warm, the Bermuda keeps growing and crowds out the young rye. Seeding in late September or early October can also push Bermuda to spend energy it needs for spring.
- Too late: once frost nights arrive, usually later in the season, tender seedlings can be damaged before they're established.
- For early November: if you want a winter lawn this year, plan to seed within the next couple of weeks rather than waiting until Thanksgiving.
Prepping the lawn before you seed
Good prep is what gets seed down to the soil, where it can sprout. Guidance from the Arizona Municipal Water Users Association (AMWUA) and local cities follows a similar schedule:
- About a month ahead: stop fertilizing the Bermuda so it starts slowing down.
- Two weeks ahead: cut back on watering. Don't shut it off completely. If you have a smart controller, switch the lawn zone to manual so it doesn't fight your plan.
- A few days ahead: stop watering so the surface is dry when you mow and seed.
- Seeding day: mow shorter than your normal height. You want the seed to reach the soil, but don't scalp the lawn down to bare dirt. Scalping can damage the Bermuda crowns that need to regrow in spring.
- Mower safety: wear closed-toe shoes and eye protection, clear rocks and sprinkler flags first, and never reach under the deck while the engine is running.
Seeding: how much and how to spread it
AMWUA suggests about 12 to 15 pounds of ryegrass seed per 1,000 square feet. To figure your lawn's size, multiply length by width in feet, or check the measurements on your plat map or HOA records.
Use a broadcast spreader and make two passes in opposite directions, like a crosshatch, so you don't end up with stripes. Then lightly rake or drag the surface to work the seed down into the grass. A thin top dressing, about a quarter inch of fine mulch or compost, helps hold moisture around the seed. If you use a bagged top dressing, follow the label, and wash your hands after handling it.
Watering new seed without wasting water
New ryegrass seed has to stay moist to sprout, so this is when a winter lawn uses the most water. The goal is short, frequent waterings, not deep soakings:
- Until it sprouts: water three or four times a day, just enough to keep the surface damp. Puddles and runoff waste water and can encourage seedling disease.
- Once you see a green haze: drop to once a day, then every other day, and keep tapering over the next three to four weeks.
- After that: water deeper and less often. The University of Arizona's AZMet weather service posts lawn watering guidance for the Phoenix area that you can use as a guide all winter.
- Mid-day checks: watch for overspray onto sidewalks, driveways and walls, and adjust heads so water stays on the grass.
- Sloped areas: break watering into shorter cycles with a break in between so it soaks in instead of running off.
First mowing, feeding and spring transition
Wait to mow until the new rye reaches about three inches, and make sure your mower blade is sharp so it cuts cleanly instead of pulling up young plants. A light feeding about two weeks after the seedlings come up helps them fill in. Follow the fertilizer label, and water it in.
In spring, the rye starts to fade as the days heat up, and the Bermuda wakes up underneath. Easing off water and mowing a bit lower as the weather warms helps the Bermuda take back over, rather than letting the two grasses compete into early summer.
When to skip it
Skipping the winter lawn is a smart, responsible choice in the desert, not a lazy one. The Water – Use It Wisely campaign estimates that skipping overseeding can save more than 8,000 gallons of water per 1,000 square feet each season. Dormant Bermuda only needs watering about once a month from November through February, and less when winter rain falls. Skipping can make sense for you if:
- You're a snowbird or travel for the holidays and can't watch the sprinklers during those first few weeks.
- Your lawn is small, narrow or mostly decorative.
- You'd like a break from mowing, bagging and running yard equipment all winter.
- Your Bermuda struggled last spring. Giving it a rest helps it store energy and come back stronger.
- You're thinking about trading some grass for desert landscaping. The City of Surprise Water Conservation office is a good place to ask about any current programs or rebates.
A green lawn or a resting one, both are fine
There's no wrong answer here. If you love a green winter lawn, overseed in the next couple of weeks, water lightly and taper off. If you'd rather save the water and the work, let the Bermuda rest and give it its monthly drink. For more seasonal tips, browse the My AZ Pro blog or sign up for our newsletter.
Whichever you choose, green or tan, enjoy those mild desert afternoons outside. And when the evenings turn chilly, My AZ Pro is here to keep your home comfortable inside. Call 833-692-9776 any time you need heating or cooling help.