1. Mowing Too Short
Scalping your lawn might look neat at first, but it invites every weed seed in Collin County to make itself at home. Bermuda grass cut below one inch loses its ability to shade the soil surface. Bare, sun-warmed soil is exactly what crabgrass and spurge need to germinate quickly.
In Frisco, the summer heat compounds this problem. A scalped lawn stressed by 100-degree days has no energy left to outcompete invaders. The general rule for Bermuda is to keep it between one and two inches during the growing season. St. Augustine wants to be taller, ideally between two and a half and four inches — and that height actually helps it choke out broadleaf weeds on its own.
Raise your mower deck. It's one of the cheapest weed-prevention tools available.
2. Over-Watering
Frisco homeowners running irrigation systems on automatic timers often water far more than their lawn actually needs. This creates soggy surface conditions that favor nutsedge and sedge varieties, both of which thrive in wet, poorly draining soil. Collin County clay soils already drain slowly — flooding them with daily irrigation makes the situation worse.
Bermuda grass is drought-tolerant by nature and prefers deep, infrequent watering: once or twice a week at most during the summer, enough to wet the soil six inches down. St. Augustine needs a bit more consistent moisture, but still not daily. Running your system every day keeps the top inch of soil perpetually moist, which is a germination bed for shallow-rooted annual weeds.
Check your controller settings at the start of each season, and reset them after rain events. Most Frisco HOA neighborhoods have restrictions on watering days anyway — use that as a framework for breaking the daily-water habit.
3. Missing the Pre-Emergent Window
This one accounts for more weed blowups than almost anything else. Pre-emergent herbicides work by preventing weed seeds from germinating. Once the seeds have already sprouted, pre-emergent does nothing.
The problem in Frisco is that most national guides suggest applying pre-emergent in late February or March. That's too late. Soil temperatures in Collin County regularly hit the 50-55 degree threshold that triggers crabgrass germination as early as mid-February in mild years. By the time the calendar says "spring treatment season," you're already behind.
The right window for Frisco is late January to mid-February for the first application, with a second application eight to ten weeks later to extend coverage through spring. Lawns that miss this window spend the rest of the summer on defense, applying post-emergent products that are harder on the turf and often less effective on established plants.
If you want to understand the full seasonal treatment calendar for North Texas, the Frisco weed control calendar breaks down every application window by month.
4. Using the Wrong Products for Your Grass Type
A herbicide labeled for general lawn use can still kill your specific grass if it's not formulated for it. This is one of the more expensive mistakes Frisco homeowners make.
St. Augustine grass is particularly sensitive. Many common broadleaf herbicides that work fine on Bermuda will damage or kill St. Augustine if applied at the wrong rate or in the wrong conditions. Atrazine-based products are commonly used on St. Augustine, but they can injure other grass types and have soil persistence that complicates things if you ever want to overseed.
Bermuda lawns have their own set of compatible products. Dallisgrass control on Bermuda requires different chemistry than crabgrass control, and mixing them up usually means treating the symptom while missing the actual problem.
If you're not sure what grass type you have or what products are compatible with it, this is exactly the kind of question that a licensed Texas Department of Agriculture pesticide applicator is equipped to answer. Guessing with herbicide chemistry rarely ends well.
5. Skipping the Fall Treatment
Spring gets all the attention in lawn care, but fall is when the most important maintenance window for Frisco lawns quietly opens and closes. A fall pre-emergent application — typically applied in September or October — targets the winter annual weeds that germinate when temperatures drop: annual bluegrass, henbit, chickweed, and others.
Frisco homeowners who skip fall treatment often wonder why their dormant Bermuda lawn looks green and weedy by December. Those are winter annuals that germinated while the grass was sleeping, establishing themselves in the soil before any spring treatment would ever be applied.
Fall is also the time to address soil compaction through aeration and to give the lawn nutrients it needs to come back strong in spring. A healthy, dense lawn is its own best defense against weed pressure. The benefits of professional lawn health programs in Frisco include this kind of year-round thinking that most homeowners don't prioritize until they're already dealing with a weed problem.
6. Ignoring Soil Compaction
Frisco's clay-heavy soils compact more aggressively than sandy soils, particularly in high-traffic areas. Compacted soil pushes water and nutrients to the surface rather than letting them reach the root zone. The result is shallow root development, thinner turf, and bare spots. Bare spots fill with weeds.
Core aeration — pulling small plugs of soil out of the lawn — breaks up compaction and allows water, air, and fertilizer to penetrate. For most Frisco lawns, annual aeration in late spring or early summer (when Bermuda is actively growing) makes a noticeable difference in turf density by the end of the season.
Thin, compacted turf can't compete. Weeds move into low-density areas faster than grass can recover. Aeration isn't a weed treatment, but it removes one of the underlying conditions that allows weeds to get ahead of the grass.
7. Spraying Herbicide in Extreme Heat
This mistake is common and understandable — summer is when Frisco homeowners are most motivated to treat weeds. But applying herbicide when temperatures are above 90 degrees creates two problems.
First, the herbicide itself can volatilize faster than the plant can absorb it, reducing effectiveness. Second, many herbicides applied in extreme heat cause stress injury to the surrounding turf, which is already under thermal stress. The result is often a lawn that shows herbicide burn alongside the target weeds, creating more bare soil that fills right back in with weeds.
The better approach is to treat in the morning, before temperatures climb, and to hold off on post-emergent applications during any stretch of consecutive 95-plus degree days. Fall and early spring treatments, applied when temperatures are moderate, are almost always more effective than mid-summer spray sessions.
For broader advice on keeping a Frisco lawn weed-free through the seasons, the Texas lawn care tips guide covers application timing, product selection, and turf management through every part of the year.
Frequently Asked Questions
Why do weeds keep coming back in my Frisco lawn even after I treat them?
The most common reasons are missed pre-emergent windows and underlying turf weakness. Post-emergent treatments kill visible weeds but do nothing to prevent the next generation of seeds from germinating. Without pre-emergent protection at the right time, and without addressing what's making the turf thin (compaction, incorrect mowing height, irrigation issues), weeds will return every season.
When is the right time to apply pre-emergent in Frisco, TX?
Late January to mid-February for the first application targeting spring annual weeds like crabgrass. A second application eight to ten weeks later extends coverage. September to October for the fall application targeting winter annuals. These windows are earlier than most national guides suggest because Collin County soil temperatures warm up faster than average.
Can I use the same weed control products on Bermuda and St. Augustine?
Not always. St. Augustine is sensitive to several herbicides that are safe on Bermuda. Always check the product label for grass type compatibility before applying. When in doubt, use a licensed applicator who knows which products are appropriate for your specific turf variety.
Does mowing height really affect weed pressure?
Yes. Taller grass shades the soil, which slows germination for many annual weeds. Bermuda cut below one inch creates bare soil conditions that invite crabgrass and spurge. St. Augustine maintained at two and a half inches or taller is dense enough to shade out a significant percentage of broadleaf weed seedlings on its own.
Is it too late to fix my lawn if weeds are already taking over?
It depends on what's there. Annual weeds like crabgrass can be managed with post-emergent treatment now and pre-emergent next season. Perennial weeds like nutsedge and dallisgrass are harder and may require multiple treatment cycles over more than one season. A lawn evaluation from a Collin County lawn care company can identify exactly what you're dealing with and whether the turf underneath is worth saving or needs renovation.
Looking for professional weed control services in Frisco? Browse the full resources guide for help choosing a licensed lawn care company in Collin County.