Weed Smooth crabgrass and large crabgrass
Scientific Name Digitaria ischaemum and D. sanguinalis
Family Grass Family (Poaceae)
Life Cycle Summer annuals
Reproduction Method Reproduce primarily by seeds. Large crabgrass can also reproduce by long, rooting tillers.
Appearance Both crabgrasses are much-branched and upright or prostrate. Large crabgrass is normally mat forming, often has purple stems, and can grow to more than 3 feet in height. Smooth crabgrass is usually 15 inches or less.
Leaves The leaves of large crabgrass are pale blue green, pubescent on both sides, and with margins that may be rough. They are flat, sharply pointed, 1/4 to 2/5 inch wide, and 2 to 6 inches long. Smooth crabgrass leaves are normally dull green, sometimes purple tinged, and with margins that may be rough. They are sharply pointed, sparsely pubescent near the base, 1 to 4 inches long, and 1/8 to 1/4 inch wide.
Flowers Large crabgrass flowers are borne in a raceme with 3 to 13 purplish finger-like spikes up to 6 inches long. They occur in whorls at end of stout stalks during August and September. The flowers of smooth crabgrass are borne in a raceme with 2 to 6 finger-like, purplish spikes up to 4 inches long, and at end of flowering stalks. They also occur August and September.
Occurrence Both crabgrasses can be found in most warm, moist, fertile lawns in sun where turf is thin or mowed too short. They will tolerate hot, dry, compacted soils after establishment, and may spread aggressively to crowd out desirable grasses.
Non Chemical Control To control without chemicals maintain turf density and health through proper culture; avoid light, frequent irrigation, spring cultivation, short mowing, and summer fertilization. They can also be hand-pulled or mechanically removed.
Chemical Control
Application Period Apply preemergence herbicides before germination when soil temperatures stabilize at 50F for several consecutive days; post emergence herbicides should be applied when plants are small.
Active Ingredient in Labeled Products

Preemergent

Postemergent

  • dithiopyr*
  • ethofumesate*
  • oxadiazon
  • pendimethalin
  • prodiamine
  • trifluralin
*Some early postemergence activity as well
  • fenoxaprop-p-ethyl
  • MSMA
  • quinclorac
Notes Seeds of both plants can germinate from mid spring through summer when soil temperatures are greater than 55 to 60F for 7 to 10 consecutive days and can continue germinating in soil temperatures to 95F. These plants reproduce from seeds found in the soil throughout much of the growing season when moisture and light are present and soil temperatures are warm

(Click on Image to Enlarge and Sharpen Photograph)

Crabgrass seedling in turf

Crabgrass mature plant

(Large) Crabgrass ligule

Crabgrass in turf

Crabgrass collar region

Crabgrass senescence

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