Broadleaf weeds are generally easiest to identify. Broadleaf weeds (like dandelion and clover) are distinctive from and are not botani-cally closely related to grasses and sedges. Broadleaf weeds have leaves that are broad, and are generally produced in pairs or multiples. Leaves are detached from the main stem
by a sub-stem or petiole. Leaves may be simple (having one leaflet, like dandelion) or compound (having more than one leaflet, like clover). Veins within the leaf give a netted appearance in most cases.
Grass weeds (like crabgrass and goosegrass) are botanically related to lawngrasses. They have a similar appearance and growth habit. Leaves of grasses are not detached from the main stem. Leaves of grasses are narrow, with a blade-like appearance. Leaves are produced one at a time in two vertical rows. Veins within leaves run parallel. Stems are usually round or flat.
Grass weeds are often very difficult to control once established in the lawn. Thus, grass weeds are generally best controlled with preventative or preemergence herbicides. Preemergence herbicides need to be applied prior to germination, as they act by preventing establishment.
Sedges (like yellow nutsedge) are not grasses ,but have leaves that are similar in appearance and are thus often mistaken for grasses. Since herbicides used to control grass weeds are generally not effective on sedges, it is important to distinguish between the two types. Sedges have two key identifying characteristics: leaves arranged in three vertical rows and a triangular stem. Stems of grasses are commonly round or flat with leaves in two vertical rows.
Life Cycles Summer Annuals
Annuals complete their life cycle within 12 months. Summer annuals generally germinate in the spring, grow or develop during the summer, produce seed and die by the fall or after the first hard frost.
Winter annuals complete their life cycle in 12 months but generally overlap two calendar years. Winter annuals germinate in late summer to early fall and begin to develop. Winter annuals are dormant or semi-dormant through the winter, and flower the following spring. Winter annuals mature and die in late spring or early summer.
Summer and winter annuals reproduce and spread by prolific seed production, serving as a ready source of infestation and establishment when conditions are favorable.
Perennials live for more than two years and may regenerate indefinitely. A simple perennial, like dandelion, may germinate from seed, but produces a tap root that, when severed, can produce a new plant. A complex perennial can spread by seed in addition to creeping above- or below-ground vegetative structures (such as stolons, rhizomes or nutlets) capable of initiating a new plant.
Perennial weeds are often the most difficult to control. You are usually trying to control an established plant that has already produced considerable vegetative reproductive structures which may require repeat control measures. Removal of the above-ground shoot growth does little towards long-term control. Long-term control usually requires herbicide treatments that act on the above- and below-ground structures.
Your choice of a best management strategy, including appropriate herbicide(s), is dependent on weed type and life cycle. The "Weed Identification" section provides pictures to help with identification. This section separates weeds common in Tennessee lawns according to type and life cycle.
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