Managing Summer Weeds Starts with Soil Health

PJC Support

As spring fades into summer, a new wave of weeds begins to emerge. Environmental stressors—like drought and extreme heat—make it difficult for cool-season turfgrasses to outcompete weeds. But don’t worry: with the right cultural practices and products, you will be managing summer weeds effectively.

When scouting lawns and athletic fields, always ask: “Why is this weed here?” The answer almost always lies in underlying soil conditions. In this post, we’ll highlight four common summer weeds that thrive in compacted soils and offer organic strategies for managing them.

1. Crabgrass

This well-known summer annual appears in two varieties: large (hairy) and small (smooth). It typically germinates from mid-spring to mid-summer and continues aggressively flowering and seeding through the first frost—making control a real challenge.

Why it thrives: Crabgrass tolerates heat, drought, and compacted soils far better than most turfgrasses. However, it struggles in shaded areas, whether from trees or a dense turf canopy.

Organic management:

Mow high to shade the soil
Water deeply but infrequently
Aerate compacted areas
Overseed with a tall fescue-dominant blend for better competition

2. Goosegrass

Often confused with crabgrass, goosegrass is a late-germinating summer annual, appearing 4–6 weeks after crabgrass. It adapts to a wide range of site conditions and thrives in nutrient-deficient, dry, and compacted soils, especially in high-traffic turf areas and landscape beds.

Why it’s a problem: Goosegrass has a low growth habit and smooth blades, creating a poor playing surface on athletic fields by affecting ball roll and traction.

Organic management:

Maintain a tall, dense turf stand
Prioritize aeration to relieve compaction
Encourage healthy root development with proper fertility

3. Prostrate Knotweed

Prostrate knotweed is often the first broadleaf summer annual to germinate, making an early spring appearance. It’s a classic indicator of compacted soils, spreading quickly to form dense mats that crowd out turfgrass.

Why it thrives: Poor soil structure gives it a competitive edge over emerging turfgrass.

Organic management:

Aerate aggressively—at least twice a year (spring and late summer/fall)
Overseed consistently to reestablish turf density
Use slice seeding on athletic fields to damage knotweed and deposit seed directly into the soil

4. Plantain

Broadleaf plantain is another strong signal of compacted soils. With deep taproots, it can break through poor structure and absorb calcium that turfgrass roots can’t access.

Why it’s difficult: Plantain thrives under a wide range of moisture conditions, making it especially persistent in high-traffic areas like athletic fields.

Organic management:

Aerate and overseed regularly
Apply gypsum to improve calcium availability and soil structure
Maintain healthy turf to outcompete new growth

Practical Prevention: Building Turf That Crowds Out Weeds

Regardless of which weeds you encounter, the best defense is a healthy, dense turf stand supported by good soil and sound cultural practices:

Mowing
Keep mowing height high. This shades out low-growing weeds and prevents light from reaching weed seeds on the soil surface.
Watering
Water deeply and infrequently to promote strong turf root growth. Avoid shallow, frequent watering that favors weeds.
Soil Testing
Monitor pH and nutrient levels regularly. Liming acidic soils improves nutrient availability and helps build better structure.
Overseeding
A diverse mix of turf species enhances resilience and outcompetes weeds.