Broadleaf weed seedling key page 1

Introduction
Identification of broadleaf weed seedlings is critical to their control. Weed species vary in their response to herbicides: therefore it is necessary to select the right herbicide to control a particular species. Controlling weeds in the early stages of growth not only increases the effectiveness of control measures, but also reduces crop losses due to weed competition. This key provides an easy and reliable means for identifying broadleaf weed seedlings. To use the key you need to understand how the key is organized and be able to recognize a few simple characteristics used to identify broadleaf weeds. Broadleaf seedlings must be examined with great care. One characteristic is seldom enough to identify the weed. The following steps will help you use the identification key and ensure correct seedling identification. 1. Collect several samples of the plant to be identified. 2. Use a hand lens when available to make characteristics easier to see. 3. Begin at the top of the key and proceed downwards. Do not miss any steps.
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Terminology

Alternate Leaves	One leaf attached per node. Newest leaf is of smaller size.
Cotyledon	Seed leaves; the first pair of leaflike structures, usually paired, appearing above ground in most dicotyledonous plants.
Entire leaf margin	Leaf margins that are smooth without sawtoothed or irregularly notched edges.
Lobe	A division or segment of a leaf.
Margin	The border or edge of any plant part.
Mealy	Covered with a small, white bran-like bloom.
Midvein	The central vein of a leaf
Node	The part of the stem from which leaves or branches arise.
Opposite leaves	Leaves attached at the same node on opposite sides of the stem. Newest leaf pair are of similar size.
Palmate	Three or more lobes or veins arising from one point.
Petiole	The stalk of the leaf.
Pinnate	Lobes or veins arranged on two sides of the midvein.
Rosette	A basal cluster of leaves in a circular form without discernable upright stem.
Toothed Leaf Margins	Sawtoothed or irregularly notched leaf edges.
Whorled	Three or more leaves attached at the same node, often arranged in a whorl around the stem.

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Plant Parts

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Leaf Arrangement on Stem


Alternate Leaves		Opposite Leaves
One leaf per node. New leaf is smaller.		Attached at the same node on opposite sides of the stem. Leaves at the same node are of similar size.
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Cotyledon and Leaf Shape


Linear	Oblong	Lanceolate	Ovate

Spatulate	Oval	Round	Kidney

	Palmately Lobed	Pinnately Lobed
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