Smooth crabgrass is the most common summer annual grass problem in managed turf. It is estimated that 90% of the crabgrass in Michigan lawns is smooth crabgrass. Smooth crabgrass lacks the hairs of large crabgrass and can be identified by its light green appearance and swollen, zig-zag nodes. Crabgrass is a summer annual that re-establishes from seed every spring. Crabgrass can be an indication of elevated soil temperatures and will often establish in last year's grub damaged areas.