Weed Identification and Characteristics
Integrated weed management (IWM) pertains to cultural and chemical controls that might be used to manage any given weed population in a lawn. One of the first steps toward integrated weed management is to identify the weeds present. While it isn’t necessary to identify every potential weedy plant in a yard or garden, focusing on the select few that are the most troublesome or occupying the largest area is worthwhile.
The identification process is begun by placing the plant into one of two broad classifications: monocot or dicot (Fig. 10.3).
Figure 10.3. Monocot (right) and dicot (left) plant classifications.
Lawn weeds may be conveniently divided into two classes based on the way in which they emerge from the seed. Monocots emerge with a single seed leaf (monocotyledon) whereas dicots emerge with two seed leaves (dicotyledon) (Fig. 10.4). The term cotyledon refers to the first leaf-like structure (seed leaf) visible after the seed has emerged from the ground. In most instances, cotyledons of dicots bear little resemblance to the normal true leaves of the plant. Cotyledons of monocots are often quite similar to future true leaves.
Figure 10.4. Monocot and dicot leaf veination.
Most monocot weeds found in turf 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 (creeping Charlie), knotweed, and plantain.
Grassy and Broadleaf Weeds
Grassy weeds and broadleaf weeds are further divided into groups according to how long they live.
- Perennial weeds have a life of more than two years, though new seeds may be produced every year (e.g., dandelion, clover, quackgrass, tall fescue)
- Biennial weeds have a life span of two years, generally storing up food reserves in the leaves and roots the first year, producing flowers and seed the second. (e.g., mullein and burdock)
- Annual weeds germinate from seed, grow, flower, and produce seed in less than one year
- Summer annuals germinate in the spring and mature in the fall (e.g., Prostrate knotweed, Prostrate spurge, crabgrass, yellow foxtail)
- Winter annuals germinate in fall or late winter and mature in late spring (e.g., Shepherd’s Purse, Yellow Rocket – sometimes known as winter cress and Pennycress [mustard family]; Downy brome [grass family].)
Effective control of weeds in turf is based on correct identification. Many books and charts are available to help identify common lawn weeds. For additional help in weed identification contact your local county extension office or visit Is this plant a weed?.
Proceed to Noxious and Invasive Weeds