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Put down a pre-emergent twice a year (fall and late winter) and water it in, pull or spray the weeds that still come up while they're small, and keep at least 2 inches of rock on the ground. Most rock yards that are "always full of weeds" are missing one of those three.
Why Arizona rock yards get so many weeds
- Two weed seasons. Winter rains bring one crop of weeds. Monsoon storms bring another in summer.
- Thin rock. Many Valley homes came with a thin layer of rock when they were built, so sunlight still reaches the soil.
- Blown-in seeds and dust. Wind and storms drop new seeds on top of the rock every year.
- Drip leaks and overspray. Anywhere that stays damp grows weeds first. Check your drip lines.
Your Arizona weed calendar
| When | What to do |
|---|---|
| Sept – Oct | Pre-emergent #1 for winter weeds. Water it in with about ½ inch of water. |
| Nov – Jan | Pull or spray winter weeds while they're small, before they go to seed. |
| Feb – early Mar | Pre-emergent #2 for summer and monsoon weeds, before nights stay above about 55–60°F. Water it in. |
| July – Sept | Monsoon weeds pop up fast after storms. Pull them while the ground is still soft, or spray. |
Step 1: Stop weeds before they sprout (pre-emergent)
A pre-emergent doesn't kill weeds you can see. It stops weed seeds from sprouting. Timing is everything: put it down before the weed season, not after.
- Granules spread with a hand or push spreader are easiest for most homeowners.
- Water it in. Pre-emergent has to get through the rock to the soil underneath. About ½ inch of water, from rain or a sprinkler, right after you spread it.
- Follow the label for how much to use, which plants it's safe around, and kids and pets.
- Don't use it on wood mulch or anywhere you plan to plant seeds soon.
Step 2: Get rid of the weeds already growing
- Pull them after a rain or a deep watering, when the soil is soft and the roots come out whole. A stand-up weed puller saves your back.
- Spray them with a weed killer while they're young. Spray on a calm day so it doesn't drift onto plants you want to keep.
- Get them before they flower. One weed that goes to seed means hundreds more next season.
Step 3: Thicken your rock
Use our free Rock Calculator to see how many tons you need. Kill and clear the weeds first, put down pre-emergent, then add the new rock on top.
Does landscape fabric help?
Sometimes. Fabric under rock slows weeds for a while, but dust and blown-in seeds settle on top of it and weeds root right there. Fabric also tends to work its way up through thin rock and look messy. For most Arizona rock yards, a thick layer of rock plus pre-emergent twice a year does more than fabric alone.
Weed supplies for DIY homeowners
These links go to Amazon. Read the label before you buy or use any weed product.
- Grampa's Weeder stand-up weed puller
- Granular pre-emergent (weed preventer)
- Hand spreader for granules
- Roundup weed & grass killer concentrate
- Roundup ready-to-use spray
- 2-gallon pump sprayer
- Thorn-resistant gardening gloves
Paid links. We may earn a commission if you purchase. More picks: best weed control tools for Arizona.
When to hire a pro
If your yard is large, badly overgrown, or you'd rather not handle weed killers yourself, a landscape maintenance company can do a fall and late-winter pre-emergent and regular weed visits. Find licensed yard maintenance pros or browse landscapers by city.
Companies that spray weed killer for hire need a license from the Arizona Department of Agriculture (not the ROC). We've checked 51 so far, with active licenses and good Google reviews: see licensed weed control companies by city. You can look up any weed company's license here.
Keep planning
Sources
- SummerWinds Nursery Arizona: Benefits of pre-emergents (citing University of Arizona guidance on watering pre-emergent through rock mulch)
- University of Arizona: Pre-emergence weed control
General guidance only. Always follow the product label. Timing can shift a few weeks depending on rain and temperatures.