Fall Overseeding in Arizona: Green Grass All Winter on Your Horse Property

The short answer: Fall overseeding in Arizona means planting a cool-season grass, most often perennial ryegrass, into your existing bermudagrass before the bermuda goes dormant for winter. The University of Arizona Cooperative Extension says October is ideal, when days run 80 to 85 degrees and nights are about 55. Done right, the ryegrass stays green from October through May, so your yard, your arena surround and the grass around your barn stay green all winter while everyone back east is shoveling snow.

This is one of my favorite times of year on horse property in the Metro Plex of Arizona. The heat breaks, the horses perk up, and the bermuda that carried us through summer starts to fade. A little fall overseeding turns that tan patch into a green carpet for the holidays. Here is the simple, step-by-step version, straight from the University of Arizona.

Bermudagrass is a warm-season grass. In the lower desert of Arizona, the UA Extension explains, warm-season grasses go dormant in winter and lose their green color. That is perfectly normal and healthy. Overseeding simply adds a cool-season grass on top so you have green through the cool months, then the bermuda takes back over in spring.

October. The UA Extension guide points to daytime highs of 80 to 85 degrees and nights around 55. Seed too early, while it is still hot, and the bermuda keeps growing and crowds out your new grass. Seed too late, and young seedlings can be hurt by frost. If you are reading this on a mid-October morning, you are right on time.

First decide what the grass is for. A green lawn around the house and a pasture your horses and cows will graze are two different jobs. For the yard, the UA Extension lists a few choices. The two most homeowners use are:

• Annual ryegrass: light green, coarse, fast growing, needs frequent mowing, and is the budget choice.
• Perennial ryegrass: deep green, narrow leaves, better frost tolerance and disease resistance. It costs more and gives a nicer winter lawn. It also hangs on longer in spring, competing with the bermuda as it greens up.

There is also intermediate ryegrass, a hybrid of the two. Finer grasses like roughstalk bluegrass and creeping bentgrass are mostly for golf greens.

Lawn ryegrass is basically golf course grass. For a pasture you want more roughage, and that means winter cereals. The UA Extension's guide to irrigated pastures in Arizona lists barley, oats, triticale and wheat as winter cereals that are "highly palatable and nutritious" and "provide much needed feed during the cooler time of year." They are often planted together, and annual ryegrass is often mixed in with oats and barley because it comes up fast.

Here is what the UA Extension recommends for the low desert:

• When to plant: October for elevations under 2,000 feet.
• Seeding rates per acre: oats 80 lb, barley 100 lb, triticale 120 lb, wheat 120 lb, annual ryegrass 30 lb. Plant the cereal seed 1 to 1 1/2 inches deep.
• When to graze: start when the cereals are 8 to 12 inches tall, take them down to about 4 inches, then rest the pasture 7 to 15 days before grazing again.
• Watch the awns: every winter cereal except oats usually has awns, the bristles at the tip of the seed head, which can irritate a horse's mouth and eyes. Graze before the plants head out, or ask for awnless forage varieties.
• Go slow at first: the UA Extension notes that bloat, nitrate toxicity and grass tetany can be a problem with winter cereals, so turn horses out a little at a time on lush new growth.

Here is the countdown from the UA Extension publication:

1. 30 days before: stop nitrogen fertilizer on the bermuda.
2. 14 days before: raise your mowing height 30 to 40 percent and cut watering by about 30 percent.
3. 1 to 3 days before: stop watering. Mow back down to your old height, then, just before seeding, lower it another 25 to 30 percent and leave the clippings as mulch for the seed.

One important note: do not scalp the bermuda down to the dirt. On thick hybrid bermuda, a light dethatch or shallow vertical mow helps seed reach the soil.

The UA Extension recommends 12 to 15 pounds of ryegrass seed per 1,000 square feet. Spread half walking one direction, then the other half walking crosswise. Lightly rake or drag it in so the seed touches soil. Measure your grass area before you shop, and your feed store run will be quick and easy.

This is where most of the magic happens. Water three to four times a day for the first 7 to 10 days, until the seedlings come up. Do not let the seed dry out. Once the grass is established, gradually stretch your watering to about once a week.

The UA Extension has a great tip for checking: push a long screwdriver into the soil. If it slides in easily about six inches and comes out damp, you do not need to water yet. If your property runs on a well or flood irrigation, plan your schedule around that. Our guides to well water on Arizona horse property and flood irrigation for Arizona owners can help.

About two weeks after the seedlings come up, the UA Extension suggests ammonium phosphate (16-20-0) at 5 pounds per 1,000 square feet, then water it in. More is not better here. Over-fertilizing can raise the chance of frost damage and disease and means extra mowing.

Mow the first time when the ryegrass reaches about 2 3/4 to 3 inches. A rotary mower set at 2 1/4 to 2 3/4 inches works well. Mow when the grass is dry and the blades are sharp.

Bermuda wakes back up once spring nights stay above 60 degrees for seven nights in a row, usually April to May. To help it take over, lower your mowing height about 35 percent, mow more often, keep watering, and feed it lightly. The UA Extension guide walks through the full transition. Then let the bermuda grow strong all summer, and you are ready to do it again next October.

• Seeding too early. Warm weather favors bermuda and starves out the ryegrass.
• Scalping to bare dirt. Lower the mower, but do not shave the bermuda to the ground.
• Letting the seed dry out. Those first 7 to 10 days of frequent watering matter most.
• Too much fertilizer. It invites frost damage and disease.
• Guessing your square footage. Measure first so you buy the right amount of seed.

Fall is a wonderful season to buy and sell horse property here, and a green yard photographs beautifully when everything else in the country looks gray. It also makes your property simply nicer to live on through our best riding months. If you are new to acreage, our first 90 days on a new horse property guide and our look at what it costs to maintain a horse property in Arizona pair nicely with this one.

I am Kim Williamson, REALTOR®, with REAL Broker, and I help buyers and sellers of horse property and acreage across the Metro Plex of Arizona. I have lived in Arizona 36 years, sold real estate here for 24 years, and I am an 8x WPRA World Champion. On my own place, I put down a winter rye pasture mix from my local seed store in Coolidge, and I add bags of whole oats to it. The oats really help it grow, and the horses love the roughage. There is something about walking out to feed on a cool October morning and seeing that first fuzz of green come up. It tells you the best season in Arizona has arrived. Plant it, water it, and enjoy every green day of it.

When should I overseed in Arizona? October is ideal, when days are 80 to 85 degrees and nights are about 55, according to the University of Arizona Cooperative Extension.

What grass is used for fall overseeding in Arizona? Perennial ryegrass is the most common. Annual ryegrass is a less expensive option with a lighter color.

How much ryegrass seed do I need? The UA Extension recommends 12 to 15 pounds per 1,000 square feet.

How often should I water new ryegrass? Three to four times a day for the first 7 to 10 days, then gradually back to about once a week once it is established.

How long does overseeded ryegrass stay green? Generally from October through May, until the bermudagrass takes back over in spring.

• University of Arizona Cooperative Extension: Irrigated Pastures in Arizona (AZ2020) Links checked October 11, 2026:

• University of Arizona Cooperative Extension, az1683, Overseeding Winter Grasses into Bermudagrass Turf (Kopec and Umeda, 2015)

Do your own due diligence. General information only. For your specific yard, your local Cooperative Extension office is a great resource.

Ready for horse property with room for green grass and good riding in the Metro Plex of Arizona? Call or text Kim Williamson, REALTOR®, REAL Broker, at 480-206-1500, or start at www.ArizonaHorsePropertyForSale.com.