Smooth crabgrass (Digitaria ischaemum) germinates from March through early May in North Carolina when soil temperatures reach 53 to 58°F at a 4-inch depth. Alternating dry and wet conditions at the soil surface in the spring encourages germination. Crabgrass germinates and grows best when adequate light and moisture are present. Stems have a prostrate growth habit and may root at the lower nodes. Smooth crabgrass is similar to large crabgrass, but the leaf blade of large crabgrass has more hairs, with short hairs on both surfaces, and scattered hairs on the edges.

Crabgrass will grow under close mowing conditions. Competition is enhanced by thin open turfgrass stands, improper mowing heights for the desired turf, summer fertilization, and light, frequent irrigation. For crabgrass control, practice procedures outlined to maintain a dense, actively growing turf.

• SEEDHEAD / FLOWER
  • raceme; 2 - 6 spikes at top of stems
• VERNATION TYPE
  • leaves rolled in the bud
    Figure 1
• LIGULE TYPE
  • membranous; 0.06 - 0.12 inches (1.5 - 3 mm) long, blunt to collar-like, slightly wavy
    Figure 2, Figure 3, Figure 4
• GROWTH SEASON / LIFE CYCLE
  • summer annual weed
• AURICLE TYPE
  • absent
• LEAF BLADE TIP SHAPE
  • sharp-pointed; smooth above, with mostly a few hairs near base, edges not hairy or sparse hairs along edge, dull green or tinged with purple
    Figure 5, Figure 6, Figure 7, Figure 8
• LEAF BLADE WIDTH
  • 0.2 - 0.4 inches (5 - 10 mm) wide
    Figure 9
• STOLON PRESENCE
  • present
• RHIZOME PRESENCE
  • absent
• COLLAR TYPE
  • often divided, distinct, few hairs at the edge
    Figure 10, Figure 11, Figure 12
• SHEATH MARGIN
  • open
    Figure 13, Figure 14
• SHEATH TYPE
  • flattened; sheath is not hairy, lower sheaths may be sparsely hairy
    Figure 15

Figure 1. Smooth crabgrass vernation.

×

Figure 1. Smooth crabgrass vernation.

Print Image

Figure 2. Smooth crabgrass ligule.

×

Figure 2. Smooth crabgrass ligule.

Print Image

Figure 3. Smooth crabgrass ligule.

×

Figure 3. Smooth crabgrass ligule.

Print Image

Figure 4. Smooth crabgrass ligule.

×

Figure 4. Smooth crabgrass ligule.

Print Image

Figure 5. Smooth crabgrass leaf blade.

×

Figure 5. Smooth crabgrass leaf blade.

Print Image

Figure 6. Smooth crabgrass leaf blade.

×

Figure 6. Smooth crabgrass leaf blade.

Print Image

Figure 7. Smooth crabgrass leaf blade.

×

Figure 7. Smooth crabgrass leaf blade.

Print Image

Figure 8. Smooth crabgrass leaf blade.

×

Figure 8. Smooth crabgrass leaf blade.

Print Image

Figure 9. Smooth crabgrass leaf blade width.

×

Figure 9. Smooth crabgrass leaf blade width.

Print Image

Figure 10. Smooth crabgrass collar.

×

Figure 10. Smooth crabgrass collar.

Print Image

Figure 11. Smooth crabgrass collar.

×

Figure 11. Smooth crabgrass collar.

Print Image

Figure 12. Smooth crabgrass collar.

×

Figure 12. Smooth crabgrass collar.

Print Image

Figure 13. Smooth crabgrass sheath margin.

×

Figure 13. Smooth crabgrass sheath margin.

Print Image

Figure 14. Smooth crabgrass sheath margin.

×

Figure 14. Smooth crabgrass sheath margin.

Print Image

Figure 15. Smooth crabgrass sheath type.

×

Figure 15. Smooth crabgrass sheath type.

Print Image