Lawn Issues & Field Guide

ConditionsLow-growing annual with bright green, boat-tipped leaf blades and white seed heads. Thrives in compacted, thin turf — very common in lawns mowed short or with poor drainage. Often confused with regular bluegrass but lighter in color.

Time of Year (Northeast)Germinates fall and early spring (soil temps 50–65°F). Most visible March–May in the Northeast. Dies in summer heat. Prevention window is September–October before fall germination.

TreatmentPre-emergent in early fall (before soil temps drop to 70°F). Post-emergent options are limited in cool-season lawns. Best long-term fix is overseeding thick turf in fall to crowd it out.

ConditionsLow-growing mat with small oval leaves and tiny white star-shaped flowers. Loves cool, moist, shaded areas with thin grass. Often found under trees or in low spots.

Time of Year (Northeast)Cool-season annual — germinates fall through early spring. Most visible March–May. Dies in summer heat.

TreatmentPre-emergent in early fall. Post-emergent broadleaf herbicide in early spring when actively growing. Thickening turf through overseeding is the best long-term defense.

ConditionsThree-leaflet leaves with white 'V' markings, white ball-shaped flowers. Fixes nitrogen — thrives in low-nitrogen lawns. Spreads via stolons and seed.

Time of Year (Northeast)Perennial — active spring through fall. Most noticeable May–September when flowering.

TreatmentApply broadleaf herbicide (triclopyr or a 3-way blend). Multiple treatments may be needed. A well-fertilized, dense lawn is the best long-term prevention.

ConditionsCoarse, light-green annual grass spreading in a star pattern. Thrives in thin, bare, compacted areas along driveways and edges. One plant can produce 150,000+ seeds.

Time of Year (Northeast)Germinates when soil temps reach 55°F (mid-April to May). Active June–September. Dies with first frost. Prevention window is March–April.

TreatmentPre-emergent herbicide (prodiamine or dithiopyr) in early spring is #1. Post-emergent (quinclorac) works on young plants. Overseed thin areas in fall.

ConditionsRound, scalloped-edged leaves with a distinctive minty aroma when crushed. Creeping stems root at nodes. Thrives in shaded, moist areas. Small purple flowers in spring.

Time of Year (Northeast)Perennial — visible year-round in mild weather. Most active March–June. Spreads aggressively in spring.

TreatmentTriclopyr-based herbicide is most effective — apply in fall when plants are moving nutrients to roots. May require 2–3 treatments. Improve sun penetration by trimming overhanging branches.

ConditionsCoarse, clumping perennial grass with wide flat blades and distinctive seed heads on long stalks. Grows in circular patches. Very tough to control once established.

Time of Year (Northeast)Warm-season perennial — most active June–September in the Northeast. Dies back in cold but regrows from roots each spring.

TreatmentSpot treat with non-selective herbicide (glyphosate) then reseed. No selective control in cool-season turf. Multiple applications needed for complete kill. Thick healthy turf helps prevent re-establishment.

ConditionsDeep taproot, toothed leaves in a rosette pattern, yellow flowers maturing to white seed heads. Common in lawns mowed too short or with thin turf. Spreads extensively by wind-blown seeds.

Time of Year (Northeast)Most visible April–May and again September–October. Perennial — returns each year from deep taproot if not killed at the root.

TreatmentPost-emergent broadleaf herbicide (2,4-D, MCPP, dicamba blend). Best applied in fall when plants transport nutrients down to roots. Repeat as needed.

ConditionsFlat, star-shaped annual grass lying close to ground. White center stem with silvery appearance at base. Very common in compacted soil, driveways, paths. Resistant to many pre-emergents.

Time of Year (Northeast)Germinates later than crabgrass — soil temps of 60°F (May–June in NE). Active July–September. Dies with frost.

TreatmentPre-emergent with oxadiazon or dithiopyr. Post-emergent options are limited. Core aeration to reduce compaction is essential for long-term control.

ConditionsRound, scalloped leaves with minty aroma. Same family as Creeping Charlie — often confused. Creeping stems, small purple flowers. Thrives in shaded, moist areas with weak turf.

Time of Year (Northeast)Perennial — most active March–June. Flowers April–June. Spreads aggressively in spring conditions.

TreatmentTriclopyr-based herbicide with a surfactant for penetration. Apply in fall or spring. Multiple applications likely needed over 2–3 seasons. Improve drainage and sun exposure.

ConditionsLight green, bamboo-like annual grass with a silvery midrib stripe on each blade. Spreads rapidly in moist, shaded areas along streams, roadsides, and woodland edges. Very invasive.

Time of Year (Northeast)Germinates late spring (May–June). Flowers and seeds in August–September. Annual — but seeds persist in soil for years. Most visible July–October.

TreatmentPre-emergent in early May. Hand-pull or mow before seed set in August. Post-emergent grass killers (fluazifop) effective. Thick native groundcovers help crowd it out in shaded areas.

ConditionsMat-forming annual with small oval leaves and tiny white flowers. Loves compacted soil — driveways, paths, playgrounds. Leaves alternate on reddish stems. Can indicate soil compaction problem.

Time of Year (Northeast)Annual — germinates very early spring (March–April). Active through summer. Seeds in fall. Often one of the first weeds up in spring.

TreatmentPre-emergent in early spring is best. Post-emergent broadleaf herbicide when young. Core aerate to relieve compaction — this is the root cause of the problem.

ConditionsBright yellow-green, grass-like plant growing faster than turf with triangular stems ('sedges have edges'). Thrives in wet, poorly drained areas. Spreads via underground nutlets.

Time of Year (Northeast)Emerges late spring when soil warms — most visible and aggressive June–September. Nutlets can remain dormant for years.

TreatmentApply sulfentrazone or halosulfuron-methyl (Sedgehammer). Multiple applications 6–8 weeks apart needed. Improve drainage. Do NOT hand-pull — it stimulates dormant nutlets.

ConditionsClover-like three-leaflet leaves (heart-shaped leaflets) with small yellow flowers. Seed pods explode and shoot seeds up to 10 feet. Very common in lawns and gardens. Can be mistaken for clover.

Time of Year (Northeast)Can grow spring through fall. Most active May–September. Perennial in warmer areas; annual further north in the Northeast.

TreatmentPost-emergent broadleaf herbicide (triclopyr). Multiple applications may be needed. Keeping lawn thick and healthy is the best preventive approach.

ConditionsBroad, oval leaves with parallel veins growing in a low rosette. Produces tall seed stalks. Very tolerant of foot traffic. Common along driveways, paths, and compacted areas.

Time of Year (Northeast)Perennial — visible spring through fall. Most active May–September. Produces seeds July–September.

TreatmentPost-emergent broadleaf herbicide in spring or fall. For best results apply when actively growing. Relieve compaction with core aeration to discourage future growth.

Conditions'Leaves of three, let it be.' Glossy, compound leaves with three leaflets. Causes severe allergic rash in most people. Can grow as ground cover, shrub, or climbing vine. White berries in fall.

Time of Year (Northeast)Perennial — leafs out in spring, most recognizable May–October. Leaves turn red-orange in fall. Urushiol oil (the allergen) is present year-round, even in dead plants.

TreatmentUse extreme caution — wear gloves and protective clothing. Triclopyr or glyphosate applied directly to cut stems. Professional removal recommended for large infestations. NEVER burn.

ConditionsSimilar to Poison Ivy but leaflets are more deeply lobed (oak-shaped). Same urushiol allergen causing contact dermatitis. Grows as shrub or vine. Less common in New England but present.

Time of Year (Northeast)Perennial — most identifiable spring through fall. Red-orange color in fall. Urushiol active year-round in all plant parts.

TreatmentSame caution and treatment as Poison Ivy. Triclopyr or glyphosate with direct stem application. Professional removal strongly advised. Do not handle bare-handed.

ConditionsTall annual with lobed leaves that have prickly margins and a row of spines on the midrib underneath. Produces small yellow flowers. Common in disturbed soil, edges, thin turf areas.

Time of Year (Northeast)Annual — germinates spring, grows through summer, flowers July–September. Can reach 5+ feet if not mowed. Produces large amounts of wind-borne seeds.

TreatmentPost-emergent broadleaf herbicide when young. Mowing prevents seed production. Thick turf crowds it out. Spot spray tall plants before they go to seed.

ConditionsSucculent, low-growing annual with thick reddish stems and flat, spoon-shaped leaves. Very drought tolerant. Actually edible! Common in vegetable beds and thin lawn areas. Thrives in heat.

Time of Year (Northeast)Warm-season annual — germinates after last frost (May–June). Most active July–August in peak heat. Dies at first frost.

TreatmentPost-emergent broadleaf herbicide while young. Hand-pulling works but all stem fragments must be removed (they re-root). Pre-emergent in spring. Mulching garden beds helps.

ConditionsArrow-shaped leaves with a sour lemony taste (edible). Small reddish flowers on upright stems. Spreads by seeds and creeping roots. Common in acidic, low-fertility soils.

Time of Year (Northeast)Perennial — most active spring and fall. Flowers May–June. Low soil pH and poor nutrition favor it.

TreatmentLime to raise soil pH if acidic. Post-emergent broadleaf herbicide. Improve fertility. Because it thrives in poor conditions, soil improvement is as important as chemical control.

ConditionsLow-growing annual mat with tiny oval leaves on branching stems. Produces milky sap when broken. Common in driveways, sidewalk cracks, and thin summer turf. Two types: prostrate and spotted.

Time of Year (Northeast)Warm-season annual — germinates late spring/early summer (May–June). Most aggressive July–September. Dies at frost.

TreatmentPre-emergent in spring is most effective. Post-emergent broadleaf herbicide when young. Hand-pull before seed set. Keeping lawn thick with summer shade-tolerant turf helps.

ConditionsSpiny, prickly leaves with purple flower heads. Can grow 2–5 feet tall. Biennial or perennial. Very deep taproot makes it hard to pull. Common along fence lines and unmowed areas.

Time of Year (Northeast)Biennial — grows as rosette first year, flowers/seeds second year. Rosettes visible fall through spring. Flowers May–August. Seeds disperse on wind.

TreatmentCut or mow at rosette stage before flowering. Post-emergent broadleaf herbicide on young plants. For large plants, cut stem and paint with herbicide directly. Mowing before seed set prevents spread.

ConditionsUpright hollow grass-like leaves with distinct onion odor when crushed. Produces small white or pink flowers. Grows from underground bulbs — very persistent. Common in lawns and turf areas.

Time of Year (Northeast)Cool-season — most visible fall through spring. Often prominent in early spring when other turf is still dormant. Goes dormant in summer heat.

TreatmentPost-emergent broadleaf herbicide with surfactant (waxy leaves repel water). Apply in fall or early spring when actively growing. Multiple applications over 2–3 seasons needed due to persistent bulbs.

ConditionsThree-lobed, toothed leaves resembling cultivated strawberry. White flowers and small red berries. Spreads by runners (stolons). Grows low and is somewhat shade tolerant. Common in thin, unmaintained turf.

Time of Year (Northeast)Perennial — flowers April–June. Berries June–July. Active spring through fall. Goes semi-dormant in winter.

TreatmentPost-emergent broadleaf herbicide in spring or fall. Triclopyr is effective. Keeping lawn dense through proper fertilization prevents establishment. Multiple treatments may be needed.

ConditionsPinkish-red threads or coral-pink mycelium on grass blades after wet periods. Irregular tan or bleached patches up to 2 feet. Most common in nitrogen-deficient cool-season turf.

Time of Year (Northeast)Spring and fall — April–June and September–November. Thrives at 40–75°F with prolonged leaf wetness from dew, rain, or irrigation.

TreatmentImprove fertility — a well-fed lawn rarely sustains serious red thread. Apply balanced nitrogen fertilizer. Fungicide (azoxystrobin) for severe cases. Avoid evening watering.

ConditionsRapid onset greasy-looking water-soaked circles or streaks. White cotton-like mycelium visible early morning. Spots appear overnight. Poorly draining areas at highest risk.

Time of Year (Northeast)Midsummer — July and August. Requires nighttime temps above 70°F with high humidity. Can destroy large areas in 24–48 hours.

TreatmentApply fungicide with mefenoxam or fosetyl-Al at first sign. Avoid excess nitrogen during heat. Improve drainage. Do NOT mow through infected areas — spreads spores.

ConditionsCircular to irregular rings of dead or dying grass 6 inches to several feet. Often "frog-eye" pattern — green center with dead ring. Attacks roots in compacted or over-fertilized lawns.

Time of Year (Northeast)Symptoms appear June–August, but infection begins when soil hits 65°F (May). Worsens with heat and drought stress.

TreatmentApply azoxystrobin preventively in May. Core aerate to relieve compaction. Raise mowing height. Avoid high-nitrogen in summer. Reseed affected areas in fall.

ConditionsLarge irregular straw-colored areas appearing almost overnight after stress events. Blades die at tip while roots and crowns stay intact — typically recovers with rain or irrigation.

Time of Year (Northeast)Most common May–July following rapid growth then drought or heat. Common in Kentucky bluegrass.

TreatmentUsually recovers with consistent irrigation. Fungicides rarely needed. Raise mowing height, keep blades sharp, water consistently in moderate amounts.

ConditionsGrass turns blue-gray or straw-colored uniformly. Footprints remain visible (lack of recovery). Distinct from disease — uniform pattern, no circular patches, recovers quickly with water.

Time of Year (Northeast)July–August heat waves. Cool-season grasses go dormant — this is healthy survival, NOT death.

TreatmentWater deeply 1–1.5 inches per week, early morning. Do NOT fertilize dormant turf. Avoid mowing stressed grass short. Raise mowing height to 3.5 inches in summer.

ConditionsStriped or linear brown patterns following mowing patterns or heavy traffic. Appears 24–48 hours after event. Does NOT spread like disease.

Time of Year (Northeast)July–August heat peaks. Any period when turf is already stressed from drought or heat increases tracking risk.

TreatmentIrrigate to help recovery. Avoid mowing in heat of day or during drought dormancy. Vary mowing patterns. Raise mowing height in summer.

ConditionsWhite or tan discoloration following frost. Often occurs when mowing or walking across frost-covered grass, crushing frozen blades. Irregular patches where frost was heaviest.

Time of Year (Northeast)Late October–November and again March–April. Shoulder seasons with unexpected freezes are high-risk.

TreatmentDo NOT mow frost-covered turf. Allow to thaw naturally. Most frost-damaged grass recovers as temps moderate. Apply light fertilizer in early spring once growth resumes.

ConditionsBright yellow-to-brown streaks or patches following the application pattern. Caused by over-application or no watering after application. Distinct from disease — follows application lines.

Time of Year (Northeast)Can occur any time fertilizer is applied. Risk highest in summer heat when turf is already stressed.

TreatmentWater immediately and deeply to flush excess salts through root zone. Mildly burned grass recovers in 2–3 weeks. Severe burns may need fall reseeding. Always water after granular applications.