How Often Should I Provide Weed Control to My Lawn in Southeastern PA?

Haven Lawn & Landscape
Dec 20, 2025
4 min read

Updated: Jan 28

Weed control is one of the most important components of maintaining a healthy lawn in Southeastern Pennsylvania, yet it is also one of the most misunderstood. Homeowners often assume that mowing regularly will prevent weeds or that one application of weed-and-feed will keep the lawn clean all year. Unfortunately, weeds in our region—including crabgrass, nutsedge, clover, wild violet, and creeping Charlie—are aggressive and require a structured, seasonal approach.

This article explains exactly how weed control should be applied based on university-backed turf research, including guidance from Penn State Extension. The recommendations below represent the most effective and scientifically supported strategy for preventing and eliminating weeds in cool-season lawns across the Main Line and Delaware County.

Why Weed Control Requires a Multi-Step Approach

Unlike fertilization, which can be handled in two or three applications per year, weed control is more complex because different weeds germinate, grow, and spread at different times. There is no single product that eliminates all weed types year-round, which is why timing is crucial.

Weeds fall into two main categories:

Annual weeds (like crabgrass) that germinate each spring.
Perennial weeds (like clover, dandelions, wild violet, and creeping Charlie) that return year after year and spread through root systems.

Penn State Extension emphasizes that weed control is most effective when combined with thick, healthy turf. Thin or nutrient-deficient lawns allow sunlight to reach the soil surface, encouraging weed germination. This is why fertilization, mowing height, watering, and soil health all directly affect weed presence.

However, even healthy lawns require a structured weed control program in Southeastern PA.

The Correct Weed Control Schedule for Southeastern Pennsylvania

For lawns in Wayne, Devon, Newtown Square, Broomall, and nearby areas, a proper weed control program consists of the following components:

Early Spring: Pre-Emergent Crabgrass Control Crabgrass is one of the most problematic weeds in our region. A pre-emergent herbicide must be applied in early spring—typically between late March and mid-April, depending on soil temperature.

This application prevents crabgrass seeds from germinating. Once crabgrass emerges, pre-emergent herbicides are no longer effective.

Penn State research shows that timing is key. Pre-emergent must be applied before soil temperatures reach 55°F for several consecutive days. Missing this window can allow crabgrass to spread rapidly through summer.

Late April - Early May: Second Pre-Emergent Crabgrass Control Although the bulk of crabgrass will not get passed the first pre-emergent application, a second application will prevent any late growing crabgrass from invading your lawn.

Late Spring: Broadleaf Weed Suppression As temperatures warm, perennial weeds such as clover, ground ivy, oxalis, and plantains become active. A post-emergent broadleaf application targets these weeds early in their growth cycle.

This application is essential because many broadleaf weeds in our area begin spreading aggressively by mid-spring.

Summer: Targeted Spot Treatments Only A healthy lawn that received proper spring care will not need blanket weed control in summer. Cool-season turf experiences heat stress in July and August, and Penn State recommends avoiding widespread herbicide applications when grass is stressed.

Instead, summer weed management should focus on:

Isolated broadleaf outbreaks
Hard-to-control weeds such as nutsedge
Areas weakened by heat or moisture issues

Spot-treating prevents unnecessary stress on the lawn while keeping problem weeds under control.

Fall: Broadleaf Weed Control During Prime Season Fall is the most effective time of year to treat perennial weeds. Weeds are actively transporting nutrients to their roots for winter survival, which means systemic herbicides are absorbed more efficiently.

A fall treatment targets:

Clover
Dandelions
Creeping Charlie
Wild violet
Chickweed
Plantains

Penn State Extension considers fall broadleaf control a critical part of long-term lawn improvement.

Why More Weed Control Is Not Automatically Better

This is where many homeowners get misled.

Large national lawn-care companies promote 7, or even 8, “weed control applications” per year. The reality is that Pennsylvania turf science does not support that frequency. Over-application does not equal better results and can increase turf stress, herbicide resistance, and unnecessary cost.

Weed control works because of:

Correct product
Correct timing
Correct environmental conditions

Not because of more frequent visits.

Haven Lawn & Landscape follows Penn State’s turf research, recommending only the treatments that cool-season lawns need to remain healthy—not a corporate package designed to maximize visit count.

Common Homeowner Mistakes That Lead to More Weeds

Many of the weed problems we see in Wayne, Devon, and Newtown Square are caused by simple management errors. Based on Penn State turf guidelines, the most common include:

Mowing too short This is one of the top causes of weed growth. Cutting cool-season grass below 3.5 inches reduces turf density and lets light reach the soil, which stimulates weed germination.

Skipping spring pre-emergent Once crabgrass emerges, it cannot be prevented. Homeowners who “wait to see weeds first” always lose the crabgrass battle.

Inconsistent fertilization Under-fertilized turf becomes thin, allowing weeds to invade.

Trying to fix weeds with one-time products Weed-and-feed or single-spray solutions rarely solve the underlying issue.

Overwatering or under-watering Moisture stress encourages weak areas where weeds establish easily.

Weed control is most effective when combined with correct mowing, fertilization, and lawn-health practices.

What This Means for Homeowners in Our Area

If your lawn consistently has weeds each year, the issue is almost always a combination of:

Missing spring pre-emergent
Weak or nutrient-deficient turf
Mowing too short
No fall broadleaf treatment
Inconsistent or improperly timed weed control

With just the right applications at the correct times, weed pressure drops dramatically—often within one season. Healthy turf also becomes increasingly weed-resistant as density improves.

Professional Weed Control Designed for Southeastern PA

Haven Lawn & Landscape structures its weed control program around the turf research published by Penn State and other university extension programs. Our approach includes: