Weed Identification and Control

Lawn weeds may conveniently be divided into two classes based on the way in which they emerge from the seed. Monocots emerge with a single seed leaf whereas dicots emerge with two seed leaves. Most monocot weeds found in turfgrass are from the family Gramineae and are termed weedy grasses. Examples include crabgrass, annual bluegrass, tall fescue, and quackgrass. Dicots, on the other hand, are termed broadleaf weeds and include such plants as dandelion, clover, ground ivy, knotweed, and plantain.

Weeds are plants growing where they are not wanted or plants growing out of place. Several turfgrasses, for example tall fescue or creeping bentgrass, may be classed as weeds when growing in Kentucky bluegrass or fine fescue turf areas. The designation of a plant as a weed may also vary according to time and cultural outlooks; clover, for example was looked upon as a common part of lawns and a potential source of free nitrogen until the 1950's.

The main reason most weeds are controlled in turf is they distract from the overall appearance of the turf. High-quality turf is often judged by its uniformity. Weeds, having different leaf shapes, sizes, colors, or growth habits, usually reduce uniformity within a turf area.

A second reason weeds are controlled is because they compete with turfgrasses for water, light, and mineral nutrients. As competitors with turfgrasses , weeds hinder turfgrass from achieving optimum growth and appearance.

A third reason for controlling weeds occurs in athletic turfs. For instance, the presence of weeds on a golf course putting green can alter the path of putted ball. Low-quality turf is generally less safe for athletes than high-quality turf because it provides less cushioning. Many low-budget football, baseball, and soccer fields have extensive populations of annual weeds. During heavy-use periods in mid to late autumn and early spring, players risk injury where weeds have died.

Specific information and recommendation are available from many different states, including:

Weed Life Cycles

Chickweed (broadleaf weed)

Weeds usually have one of three life cycles: annual, biennial, or perennial.

Annual weeds live for a single season. There are two types of annuals and both reproduce by seeds. Cool season (or winter) annuals germinate in late summer or fall, are dormant during the winter, flower in spring or early summer, and then die. Chickweed (Stellaria media) is an example of a cool season annual weed. Warm season (or summer) annuals germinate during spring or summer, flower, and die at the end of that growing season. Crabgrass (Digitaria spp.), goosegrass (Eleusine indica), spurge (Euphorbia supina), knotweed (Polygonum aviculare), and yellow foxtail (Setaria glauca) are examples of warm season annual weeds.

Biennial weeds live for two seasons. During the first growing season, these weeds remain in a vegetative phase. Following a cold treatment (vernalization), biennial weeds bolt, flower, set seed, and die during the second growing season. Wild carrot (Daucus carota) and bull thistle (Cirsium vulgare) are examples of biennial weeds in turf.
Purslane (broadleaf weed)

The Dandelion (broadleaf weed) Perennial weeds live for multiple season and flower more than once. Perennial structures (rhizomes, stolon, crowns, entire plants, nutlets, or roots) survive from year to year. Wild garlic (Allium vineale), yellow nutsedge (Cyperus esculentus), quack grass (Elytrigia repens), ground ivy (Glechoma hederacea), yellow woodsorell (Oxalis stricta), buckhorn plantain (Plantago lanceolata), broadleaf plantain (Plantago major), dandelion (Taraxacum officinale), white clover (Trifolium repens), and violet (Viola spp) are examples of perennial weeds.

While the thought of hand-weeding an entire lawn may send twinges up your back, this may easily be the safest removal method for small numbers of broadleaf weeds scattered through a lawn or on or two small weedy patches. Try to get as much as possible of the root system of perennial weeds.

Cultural Practices

A dense, healthy turf is the best defense against weeds. Therefore mowing at a higher height is beneficial to the lawn. Longer grass shades the soil surface keeping it cooler, helping it retain moisture, and making it difficult for weeds to germinate and grow. The rule of thumb is to mow often enough that you never cut off more than one third of the height of the grass blades.

Correct irrigation is also a very important factor in dealing with lawn weeds. With the correct watering practices the turf will become very lush, healthy, and weedless.

	Introduction
	Weed Life Cycles
	Cultural Practices
	Weed Classification
	Weed Control Methods
	The Grand Principle: Do The Most With the Least
	Using Weeds as Indicators of Turf Management and Environmental Conditions

Introduction

Weed Life Cycles

Cultural Practices

The Grand Principle: Do The Most With the Least

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