Weeds are simply plants that are in the wrong place, notes the University of Minnesota Extension. They plague not only private landscapes, but are also the main problem on golf courses and sports fields. These uninvited plants damage a grass turf's uniformity, requiring time and expense in maintenance. The first step in solving lawn weed problems is identifying a weed and then deciding why it's a problem, says the University of Illinois.
The three main types of lawn weeds are grassy, broadleaves and sedges, says Texas A & M University. Grassy weeds have hollow, joints and the veins of their leaf blades run parallel to leaf margins. This weed is much longer than it is wide and has mutli-branching, fibrous roots.
Broadleaved weeds typically have showy flowers with leaves containing a network of veins that run at diverse angles. Sedges, which have a grass-like appearance, have stems with three sides that are triangular-shaped.
Crabgrass is light green and has reddish-purple stems. This weed forms seed-heads, consisting of fingerlike, thin spikes, notes Colorado State University.
Blue mustard, which resembles a dandelion, has a rosette with lobed leaves and blue or purple flowers.
Bindweed, also called creeping jenny or wild morning glory, is a creeping perennial weed with arrow-shaped leaves and attractive white or pink blooms.
Weeds are annuals, biennials or perennials, notes Purdue University. Annual weeds, which complete their life cycle in one single season, are either cool season or warm season plants. Chickweed is a cool season annual. Warm season annuals include crabgrass, spurge, yellow foxtail and knotweed.
Biennial lawn weeds live for two growing seasons. Bull thistle and wild carrot are examples of biennial weeds.
Perennial weeds, which live for several seasons and flower several times, include wild garlic, quack grasses, dandelions, white clovers, ground ivies and yellow nutedges.
Ground ivy or creeping Charlie can quickly invade shaded lawns with poor soil drainage. On the other hand, knotweed is a weed that can survive in soils that are compacted, notes the University of Illinois. Lawns watered too frequently or mowed too short can be attacked by crabgrass. Clover may indicate a lawn with low fertility. Dandelions can adjust to a wide variety of lawn conditions.
Lawn weeds are known for hiding, warns Garden Counselor Lawn Care.com. They appear when gardeners are not prepared to deal with the problem. By the time they arise, they're already mature, ready to re-seed.
Although lawn weeds may be the same weeds as found in a flowerbed, they must be dealt with more restrictively. While mulch is effective in controlling weeds in a non-lawn area, a non-selective weed killer can't be used.