Wide blade grasses disrupt a manicured lawn’s uniform texture and color. These invasive plants compete directly with desirable species for sunlight, water, and nutrients, leading to patchy and less healthy turf. Successfully eliminating them requires a strategic approach that begins with correctly identifying the invader and understanding its life cycle. Control is complicated because most chemical treatments designed to kill grasses are non-selective, meaning they will also damage the surrounding desirable turf. Effective removal relies on selecting highly targeted methods and implementing consistent, long-term turf management practices to prevent re-infestation.
Identifying the Common Wide Blade Invaders
The most effective removal strategy depends entirely on whether the invader is an annual or a perennial. The warm-season annual crabgrass (Digitaria spp.) is the most recognized culprit, characterized by sprawling, light-green foliage that grows in low clumps. Its blades are broader than fine turf and possess tiny hairs, and its stems resemble the legs of a crab.
A more tenacious problem is dallisgrass (Paspalum dilatatum), a coarse, grayish-green perennial that forms thick, upright clumps. Dallisgrass spreads aggressively via short, tough rhizomes and is distinguished by tall seed heads featuring multiple spikes that often display distinctive black spots.
Quackgrass (Elymus repens) is a third challenge, identified by its blue-green, flat, and thick leaves that grow upright. This perennial spreads through an extensive network of underground runners, or rhizomes, making it extremely difficult to remove.
Targeted Chemical Control Methods
Chemical control uses two primary strategies: pre-emergent and post-emergent applications, targeting different stages of the weed’s life cycle. Pre-emergent herbicides prevent the germination of annual weeds like crabgrass by forming a chemical barrier in the top layer of the soil. Active ingredients like prodiamine or dithiopyr must be applied in early spring before soil temperatures consistently reach 55 degrees Fahrenheit, the threshold for crabgrass seed germination.
Dithiopyr is unique because it also offers a short window of early post-emergent control, targeting crabgrass seedlings up to the two-leaf stage. For established weeds that have already emerged, selective post-emergent herbicides are necessary to avoid killing the surrounding lawn. Quinclorac is the most common and effective selective chemical for targeting actively growing crabgrass.
Perennial wide blade grasses like dallisgrass and quackgrass require a different approach, as their established root systems are impervious to pre-emergents. Selective post-emergent chemicals containing sulfosulfuron or foramsulfuron are options for warm-season turf types like Bermudagrass and Zoysiagrass. Fluazifop-p-butyl can suppress perennial grasses in tall fescue and fine fescue lawns but often requires multiple applications for complete control due to robust root structures.
When perennial weeds are scattered, the most practical method is targeted spot treatment with a non-selective herbicide like glyphosate. This chemical is absorbed by the foliage and translocated throughout the entire plant, including the rhizomes. This method will also kill the desirable turf it contacts, requiring the area to be reseeded or resodded after the weed has died. Always follow the product label instructions precisely, as application rates and timing vary significantly depending on the specific chemical and the type of turfgrass.
Non-Chemical and Cultural Removal Techniques
Manual removal is a feasible option for small, isolated patches, but it must be done meticulously. For annuals like crabgrass, pull the plant before it sets seed, ensuring the entire crown is removed from the soil. Perennial weeds require digging out the entire root system, including all underground rhizomes, to prevent rapid regrowth.
If even a small piece of a quackgrass or dallisgrass rhizome remains, the plant will regenerate, requiring the infected area to be excavated to a depth of several inches. For larger, dense patches, soil solarization is an effective technique that uses the sun’s energy to kill the plants. This process involves thoroughly watering the area and covering it with a sheet of clear plastic (typically 2 to 6 mil thick) for four to eight weeks during the hottest part of the year.
The clear plastic traps solar radiation, raising the soil temperature to lethal levels (often between 102 and 140 degrees Fahrenheit), which kills the weeds and their seeds. Another non-chemical option for spot treatment is using horticultural vinegar (high concentration acetic acid) or boiling water. These methods are non-selective; they instantly burn the foliage and kill surrounding turf, and they may not always destroy the deep root systems of perennials.
Long-Term Prevention Through Turf Management
The most sustainable method for preventing recurrence is maintaining a dense, healthy lawn that naturally crowds out weeds. Mowing practices play a substantial role; raising the height of the cut to between three and four inches encourages taller turf. This taller grass shades the soil surface, preventing sunlight from reaching weed seeds and inhibiting germination.
Proper watering techniques also contribute to turf health. Deep, infrequent watering encourages the lawn’s roots to grow deeper, making the turf more competitive against shallow-rooted weeds. Conversely, frequent, light watering promotes shallow roots and creates an ideal environment for weed seeds to germinate.
Maintaining optimal soil health through regular fertilization and aeration ensures the lawn remains dense and vigorous. A thick stand of turfgrass provides a natural barrier against weed invasion, making it difficult for wide blade grass seeds to establish themselves.