Lawn Weed Control in the Salinas Valley, Season by Season

Weed control in a Salinas Valley lawn starts in late winter, because that is when crabgrass and spurge begin to sprout, and it turns in fall, when annual bluegrass and clovers take their turn. Each weed points to a lawn problem. Fix that problem first, then time any herbicide to the weed's season.

The seasons and causes below come from the University of California Statewide IPM Program (UC IPM). The local notes are ours. We treat lawns in Salinas and across Monterey County, where, as our lawn treatment page puts it, "Central Coast lawns push hardest March through October."

Why do weeds take over a lawn?

Weeds move into thin, stressed turf. UC IPM says weeds "rarely become problems in well-managed, healthy turfgrass," and that poor fertilization, watering and mowing "can weaken turfgrass and make it susceptible to weed invasion," so the grass gets fixed before the weeds.

UC IPM lists the causes: weeds "often invade turfgrass that is over- or under-watered, improperly fertilized, improperly mowed, or highly compacted."

Local soil makes it worse. Our lawn treatment page notes that "Salinas Valley clay compacts," while "coastal lawns lean on overseeding to stay dense." UC IPM says soil compaction "restricts the flow of oxygen, water, and nutrients into the roots," which weakens the grass.

Which weed is it, and what is it telling you?

The weed you see points to the problem behind it. UC IPM's table of special lawn weeds pairs each one with the condition that favors it. These are the ones that matter in a Salinas Valley lawn, with UC IPM's cultural fix:

Several of these share two causes: too much water and compacted soil. If annual bluegrass and knotweed share a lawn, the soil and the sprinkler schedule need attention before anything gets sprayed. Our guide to efficient lawn watering in Salinas covers the schedule side.

Nutsedge is a special case. UC IPM says its presence "often indicates drainage is poor, irrigation is too frequent, or sprinklers are leaky." Since leaky sprinklers are on that list, a patch near one sprinkler head can point to a leak. Our irrigation audit runs every zone and flags "broken heads, leaks, and coverage gaps."

What should happen in late winter?

Late winter is the window for pre-emergent, before the first weeds sprout. UC IPM says Central Coast crabgrass "begins to sprout in early February to mid-March," and that the key to success is applying pre-emergent "2 to 3 weeks prior to weed germination."

Crabgrass is the main target. UC IPM describes both crabgrass species as "summer annuals that grow from seed each year." They start to germinate when soil temperatures reach 55 degrees F "for several consecutive days, providing there is adequate soil moisture." On the Central Coast, growth and new germination "may then continue throughout summer and into fall."

Spotted spurge runs on a similar clock. UC IPM says preemergent herbicides "can help prevent spotted spurge outbreaks if you apply them in late winter before weed seeds germinate," timed before the soil passes 55 to 60 degrees F "at a depth of 1 inch."

Our lawn treatment FAQ answers the same question this way: pre-emergent goes down "before the spring weed flush," which on the Central Coast is "typically late winter into early spring," with "a follow-up timing for summer weeds."

Three UC IPM rules decide whether a late-winter treatment works:

If the lawn is thin, plan around one trade-off. UC IPM warns that "overseeding or reseeding lawns may not be possible for several weeks or months after applying a preemergence herbicide." A lawn that needs new seed and weed prevention in the same spring needs a plan for which comes first.

What do spring and summer bring?

Spring and summer bring the warm-season weeds: crabgrass that escaped, spurge, nutsedge and dandelions. Pre-emergent no longer helps against plants already up, so hand removal, better watering and spot treatment do the work.

Summer watering matters too. UC IPM says "watering established turfgrass lightly and frequently creates a shallow-rooted lawn," which leaves room for crabgrass.

What changes in fall and winter?

In fall, the weeds change. Crabgrass dies back, and cool-season weeds start: annual bluegrass and clovers. On the coast, some of them never fully leave.

Fall is also the time to go after tough perennial grasses. UC IPM says bermudagrass, dallisgrass and knotgrass in a tall fescue lawn "are extremely difficult to control." Treatments that reach them "must be applied when weeds are actively growing and are most successful when applied in early fall before the weedy grass goes into dormancy." Those products also kill turf, so UC IPM says to "make spot treatments."

For a lawn that is badly infested, UC IPM says "it may take three applications per year (early fall, late winter and mid-spring)" to clean it up. It adds that herbicides "should not be needed year after year, if cultural practices are modified to favor the turfgrass."

When is an herbicide the right call?

Use an herbicide only after you know the weed and have fixed what let it in. UC IPM says "if your lawn is properly maintained, herbicides will generally not be necessary," and that "no single herbicide will control all lawn weeds."

The first choice is selective or nonselective. UC IPM says selective herbicides "kill target weeds without damaging desirable turfgrass species," while nonselective products "kill all or most vegetation."

Read its safety cautions before any spray:

UC IPM also notes that "some of the pesticides listed are only available for use by licensed pesticide applicators." Corn gluten meal is "often marketed for weed control," but UC IPM reports that "in experiments conducted on California lawns, corn gluten meal did not provide satisfactory weed control."

What works without spraying?

In a healthy lawn, hand weeding, the right mowing height and clean equipment can be enough. UC IPM says hand pulling "may be all that is necessary if you practice regular and proper maintenance procedures," as long as weeds come out young.

Clover and burclover point to low nitrogen, so look at the feeding program. Our soil testing guide covers what a test can show about the soil under the lawn.

When does a weedy lawn need renovation?

When a lawn is mostly weeds, it may need replanting. UC IPM says "if your lawn is primarily weeds, a complete renovation may be necessary," and that a small, fully infested area can get a partial renovation instead.

Before replanting, UC IPM says to "identify the reasons why the lawn became weedy." It also says to "correct the problems that allowed weeds to invade your lawn previously." Our lawn treatment page says a weedy-lawn program "pairs well with sod renovation where a lawn is too far gone." See sod installation.

How do we handle weed control?

We start with what the lawn shows. Our lawn treatment page describes the first visit: "we evaluate turf health, weed pressure, and soil compaction, test pH where useful, and quote a program in writing."

The plan: "pre-emergent before the spring flush, balanced feeding through the growing months, aeration and overseed when they'll take." For a lawn that is already weedy, our crews use "post-emergent treatment" to knock down existing weeds, "then feeding and overseeding thicken the turf so it crowds new weeds out."

"Each visit is logged with exactly what was applied," and we offer low-toxicity or fully organic products by request. See our lawn fertilization and weed control service, or start on our contact page for a walkthrough and a written program.

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