Lawn Care
Five Leaved Weed Spot-Treatment: Killing Common Cinquefoil
Identifying the Five Leaved Weed: Is It Common Cinquefoil?
When homeowners spot a sprawling, low-growing broadleaf weed with five distinct leaflets, they are almost always looking at Common Cinquefoil (Potentilla simplex). Often referred to colloquially as the five leaved weed, this perennial broadleaf is a notorious invader of thin, compacted, and nutrient-deficient lawns. Unlike shallow-rooted annuals, cinquefoil develops a deep, woody taproot and spreads laterally via above-ground stolons, making it highly resilient to drought and casual mowing.
Accurate identification is the first step in effective spot-treatment. Misidentifying this weed can lead to the application of ineffective herbicides and wasted resources. According to the USDA Plants Database, Potentilla simplex is native to eastern and central North America and thrives in disturbed, low-fertility soils.
Visual Diagnostics: Cinquefoil vs. Lookalikes
| Feature | Common Cinquefoil (Five Leaved Weed) | Wild Strawberry | White Clover |
|---|---|---|---|
| Leaflet Count | 5 (palmate) | 3 (trifoliate) | 3 (rarely 4) |
| Leaf Margins | Sharply toothed/serrated | Coarsely toothed | Smooth/oval |
| Flowers | Yellow, 5 petals (1/2 inch) | White, 5 petals | White/pink spherical clusters |
| Root Structure | Deep taproot + stolons | Shallow fibrous + stolons | Fibrous + stolons |
The Tug-Test Diagnostic
Grab the center of the weed rosette and pull gently. If you feel immediate resistance and the plant snaps at the crown, leaving a thick, carrot-like root in the ground, you are dealing with cinquefoil. Wild strawberry and clover will typically uproot entirely with a shallow, fibrous mat attached.
Why the Five Leaved Weed Invades (And How to Starve It)
Cinquefoil is an indicator weed. Its presence signals specific soil deficiencies that must be corrected to prevent reinfestation. The University of California Integrated Pest Management (UC IPM) program notes that broadleaf weeds like cinquefoil exploit lawns suffering from severe nitrogen deprivation and soil compaction.
- Low Nitrogen: Cinquefoil requires very little nitrogen to survive. When your turfgrass is starved of N, it thins out, allowing the weed's stolons to root at the nodes and claim territory.
- Soil Compaction: Turfgrass roots suffocate in compacted clay, but cinquefoil's aggressive taproot can penetrate hardpan layers up to 8 inches deep, accessing moisture unavailable to your grass.
- Acidic Soil: While adaptable, cinquefoil favors slightly acidic soils (pH 5.5 - 6.2). Most cool-season turfgrasses prefer a pH of 6.5 to 7.0.
Chemical Spot-Treatment Protocols for Cinquefoil
Broadcast spraying an entire lawn for localized cinquefoil patches is environmentally irresponsible and economically inefficient. Spot-treatment targets the weed directly while preserving surrounding turf. Because cinquefoil leaves possess a slightly hairy, waxy cuticle, herbicide uptake is naturally restricted. You must use the correct active ingredients combined with a surfactant.
Recommended Herbicide Formulations
As of 2026, single-active-ingredient herbicides like basic 2,4-D are largely ineffective against mature cinquefoil. You need a multi-mode-of-action product.
- SpeedZone (Carfentrazone + 2,4-D + MCPP + Dicamba): This is the gold standard for fast burn-down of tough broadleaves. The carfentrazone causes rapid cell membrane disruption, visible within 24 hours, while the systemic hormones kill the taproot over 14 days. Cost: ~$48 for a 20oz concentrate.
- Trimec Classic (2,4-D + MCPP + Dicamba): A reliable, slightly slower-acting three-way herbicide. Better for cooler spring applications when temperatures are below 70°F. Cost: ~$35 for a 32oz concentrate.
- Triclopyr (Ortho WeedClear): Highly effective on woody and semi-woody broadleaves. Excellent for late-summer spot treatments when the weed is storing carbohydrates in its taproot. Cost: ~$22 for a 32oz ready-to-spray bottle.
Critical Mixing & Application Rules
- Surfactant is Mandatory: Add a non-ionic surfactant (NIS) at 0.25% v/v (approximately 1/2 teaspoon per gallon of mix). Without this, the herbicide will bead up and roll off the hairy cinquefoil leaves.
- Nozzle Selection: Use a flat-fan nozzle (e.g., TeeJet 8002) calibrated to 20-30 PSI. High pressure creates fine droplets that drift onto desirable ornamentals.
- Temperature Limits: Never apply ester-based herbicides (like SpeedZone) when ambient temperatures exceed 85°F. The chemicals will volatilize into a gas and damage nearby trees and shrubs.
Organic and Non-Chemical Eradication Methods
For homeowners managing organic lawns, pets, or sensitive ecosystems near waterways, synthetic auxin herbicides are off the table. Eradicating the five leaved weed organically requires a combination of oxidative stress and mechanical extraction.
Iron HEDTA (FeHEDTA) Applications
Iron HEDTA (found in products like Fiesta and Natria Lawn Weed Control) exploits the physiological differences between monocots (grass) and dicots (broadleaf weeds). Broadleaves absorb the chelated iron rapidly, leading to fatal oxidative stress and tissue necrosis, while grass safely sequesters the excess iron.
Application Protocol: Iron HEDTA is a contact herbicide; it does not translocate to the taproot. You must apply it at a rate of 3 to 4 fluid ounces per gallon of water, thoroughly coating the leaves until wet. A second application is strictly required 14 to 21 days later to kill the regrowth from the surviving taproot. Expect to spend roughly $35 per gallon of concentrate.
Mechanical Extraction: The Fiskars Method
Pulling cinquefoil by hand guarantees failure; the taproot will snap, and the weed will regenerate within three weeks. Use a specialized extraction tool like the Fiskars 39-Inch Steel Stand-Up Weeder.
Execution Steps:
1. Water the lawn deeply the night before to soften the top 6 inches of soil.
2. Position the serrated claws of the weeder directly over the center crown of the cinquefoil.
3. Step fully onto the foot platform, driving the claws 4 inches into the soil.
4. Pull the handle backward to lever the entire taproot out of the ground.
5. Inspect the extracted root. If it lacks the tapered, woody tip, use a soil knife to dig out the remaining fragment.
Post-Treatment Lawn Recovery and Prevention
Killing the five leaved weed leaves bare spots in your turf that will quickly be colonized by crabgrass or new weed seeds if left untreated. Recovery must begin within 48 hours of the weed turning brown.
- Core Aeration: Rent a walk-behind core aerator to pull 3-inch plugs from the soil. This relieves the compaction that invited the cinquefoil in the first place and creates seed-to-soil contact.
- Overseeding: Apply a premium turf-type tall fescue or Kentucky bluegrass blend at a rate of 5 to 8 lbs per 1,000 square feet. Choose cultivars with high shade and drought tolerance to outcompete future weed invasions.
- Targeted Fertilization: Apply a starter fertilizer high in phosphorus (e.g., 18-24-12) to promote rapid root development in the new grass. Once established, maintain a rigorous nitrogen schedule of 2 to 3 lbs of N per 1,000 sq ft annually to keep the turf canopy dense enough to shade out germinating cinquefoil seeds.
Troubleshooting Treatment Failures
If the five leaved weed returns after chemical treatment, evaluate these common failure points:
1. Drought Stress Application: If you sprayed during a dry spell, the weed's stomata were closed to conserve water, preventing systemic herbicide translocation to the taproot. Always water the lawn 24 hours before applying systemic herbicides.
2. Mowing Too Soon: Mowing within 48 hours of application removes the treated leaf tissue before the herbicide has time to travel down the stolon to the root system. Wait at least 3 days post-spray to mow.
3. Incomplete Organic Coverage: When using Iron HEDTA, missing even 20% of the leaf surface allows the plant to photosynthesize enough energy to push new growth from the taproot.
