When a plant grows where it is not desired, it is considered a weed, and these unwanted intruders disrupt the uniform appearance of turfgrass. Successfully removing a weed from a lawn begins with accurate identification, as different species require specific control methods. Weeds belong to distinct biological categories that determine their physical structure and growth patterns. Learning to distinguish these categories helps a homeowner select the appropriate treatment strategy, preventing ineffective applications of herbicides. The physical characteristics of these plants are the clearest indicators of their identity.
Identifying Weeds by Growth Type
The systematic classification of weeds relies on fundamental structural differences, which affects their visual appearance and how they respond to treatment. Weeds are broadly grouped into three categories: broadleaf, grassy, and sedge. Broadleaf weeds are easily distinguished because their seedlings emerge from the soil with two cotyledons, or embryonic leaves. These plants typically feature leaves that are wider than grass blades, often with a net-like or branching pattern of veins.
Grassy weeds are classified as monocots, meaning they emerge with only one cotyledon. Their leaf structure displays parallel veins that run the entire length of the blade. The stems of grassy weeds are typically round or slightly flattened in cross-section and are often hollow, similar to desirable turfgrass.
Sedges represent a third category often mistaken for grasses due to their similar, blade-like leaves. The most distinguishing feature of a sedge is its stem structure, which is solid and distinctly triangular when rolled between the fingers. This characteristic “three-sided” stem sets sedges apart from the round, hollow stems of true grasses.
Common Broadleaf Invaders
Broadleaf weeds are perhaps the most recognizable group, featuring diverse leaf shapes and flower colors that stand out against the backdrop of turf.
The common dandelion is identifiable by its deeply lobed leaves that form a flat rosette close to the ground, giving them a jagged, tooth-like appearance. A dandelion produces a bright yellow flower atop a single, hollow stem, and is anchored by a thick taproot. When the leaves or stem are broken, a milky white sap is exuded.
White clover is easily spotted by its signature compound leaves, each composed of three small, rounded leaflets. These leaflets often display a pale crescent near their center, and the plant produces clusters of small, globe-shaped white flowers. White clover grows low to the ground and spreads through creeping stems, often indicating that the lawn soil is low in nitrogen.
Broadleaf plantain is characterized by thick, oval leaves with distinct, prominent parallel veins. These leaves grow in a low-lying, flat rosette, which helps the plant evade mower blades. A slender, leafless flower stalk emerges from the center of this rosette, bearing tiny, inconspicuous greenish flowers. Plantain often thrives in compacted or damp soil.
Distinguishing Grassy and Sedge Weeds
Grassy and sedge weeds are more challenging to identify since their leaves resemble turfgrass, but subtle visual cues reveal their identity.
Crabgrass is a warm-season annual grassy weed that grows in unsightly, sprawling clumps, radiating out from a central point. Its leaf blades are noticeably wider and coarser in texture than most lawn grasses, and the plant often has a dull green color that contrasts with the surrounding turf. A closer inspection of crabgrass reveals a membranous ligule, a small flap of tissue, at the junction where the leaf blade meets the stem.
Sedges, such as yellow nutsedge, are perennial plants that often appear as light green or bright yellow-green patches. They grow conspicuously faster than the surrounding lawn, causing nutsedge leaves to stand taller just a few days after mowing. The most definitive identification method is to feel the stem, which is triangular in cross-section, a feature described by the saying, “sedges have edges.”
Unlike crabgrass, nutsedge lacks a ligule and reproduces through underground tubers, called “nutlets,” in addition to seeds. The stems of nutsedge are solid. These structural distinctions mean that sedges must be treated with specialized herbicides, as common grassy weed controls are often ineffective against them.