What Is the Tall, Fast-Growing Weed in My Lawn?

Lawn weeds are an ongoing problem for homeowners. These tough and adaptable plants take advantage of any bare spot in lawns, root firmly and seed profusely to create and even bigger problem. Newly established lawns that are in the process of filling in are particularly susceptible to weed problems.

Identifying the tall, fast-growing weed in your lawn, and all the other weeds, will help you to find the right herbicide to combat it.


Dallisgrass, Paspalum dilatatum, is a tufted perennial plant that forms unsightly clumps in lawn turf. It is a coarse-textured grass that grows much faster than turfgrass. Dallisgrass bears a flowering stalk that can grow up to 65 inches high that disperses abundant amounts of seed. The seeds germinate in spring and summer and are carried to other areas by lawnmowers, water and animal movement. It is often found growing in wet areas.


Broadleaved plantain, Plantago major, is a perennial weed that sometimes acts as an annual or biennial plant. It grows as rosettes of leaves and leafless spikes of inconspicuous flowers that are simply a seedhead. These weeds can grow quickly in landscapes areas, gardens, orchards or on footpaths. Leaves may be hairless or with sparse hair. Flower heads can reach 8 inches tall, not counting the stalk, according to the University of California Integrated Pest Management Program site.


Congongrass, Imperata, is a weedy grass that can grow up to 6 feet tall and 1 inch wide, according to the University of Georgia congongrass site. It spreads by rhizomes that grow into dense mats. Leaves grow from ground level with no apparent stems. Flower heads are cylindrical and silvery-white. They grow from 2 to 8 inches long and contain many light, fluffy seeds similar to dandelion heads.


Torpedograss, Panicum repens, is an invasive weed that is a serious problem in some states like Florida. It grows near shallow water and in open areas, quickly taking over by spreading rhizomes and forming dense mats that impede water flow and obstruct shorelines. Torpedograss can grow up to 3 feet tall with sharply-pointed, torpedo-like leaf tips. Leaf blades are thin and stiff with a panicle-type flowering part that can reach 3 to 9 inches long, according to the University of Florida site.


Sporabolus indicus, commonly called smutgrass, is a perennial weed that is very hardy and can overtake lawn areas. It is called "smutgrass" because of the dark-coloured fungus that often grows on the seedhead and upper leaves. When left unmowed, smutgrass can reach 25 inches tall. Stems are wiry and can resist mowing. Smutgrass thrives in dry areas and is difficult to control.