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Scout Info
Kentucky IPM Pest Information Pages

An Introduction to Broadleaf Weeds : Kentucky IPM

An Introduction to Grasses and Broadleaf Weeds

Helpful Hints To Identifying Grasses

Grass: a narrow-leaved plant

Most plants having narrow leaves with parallel veins are called grasses. Seedling grasses are generally more difficult to identify than seedling broadleaf weeds. As grasses grow they usually develop features that help distinguish them from one another.

Parts of a Grass Plant

The leaf of a grass plant is composed of three basic parts:

  • The blade is the flattened portion of the leaf.

  • The collar is the junction between the blade and the sheath.

  • The sheath is the portion of the leaf surrounding the stem.
Parts of a Grass Plant
Other parts of the leaf are:

  • The ligule is a membrane-like structure attached to the collar on the inside of the leaf.

  • The auricles are claw-like appendages attached to the collar and surrounding the stem.

Key factors in identifying many grasses are the presence or absence of ligules and auricles and their size and shape.

Examples of leaf pubescence

Identification of grasses is also aided by the presence of hairs (called pubescence) on various plant parts. Length, density and location of these hairs will vary for different grasses. The absence of hairs (called glabrous) on parts of the plant can also serve as a key in identification of the plant.

Broadleaf Weeds

Broadleaf weed diagram

The term broadleaf weed usually pertains to weeds with broad or wide leaves and a pair of cotyledons, or seed leaves.
Seed leaves or cotyledons are usually the first pair of leaves to appear as the plant emerges through the soil. Some broadleaf weeds have large square seed leaves.

Other broadleaf weeds have seed leaves of another shape. Seed leaves are normally thicker and more fleshy than leaves that develop later. The size, shape and sometimes the odor of seed leaves can be used to distinguish some broadleaf weeds from one another.

seedling with square cotelydons
seedlings with narrow cotyledons

One key that aids in the identification of broadleaf weeds is the arrangement of the leaves. The arrangement of the leaves on a plant will vary for different species. Some broadleaf weeds have leaves arranged alternately on the stem, some have leaves arranged opposite each other, and some have leaves arranged in a whorl about the stem.Leaf arrangement types

This site was created and is maintained by Pat Dillon, Department of Entomology, University of Kentucky, S-225 Agricultural Science Ctr North, Lexington, KY USA  40546-0091 (phone: 859/257-3571). Please send questions or suggestions to: pdillon@uky.edu