WEED IDENTIFICATION - TERMINOLOGY C. Shumway B. Scott
THIS IS A GLOSSARY OF TERMS USED IN THE IDENTIFICATION OF WEED SPECIES. PROPER IDENTIFICATION IS A KEY COMPONENT ON THE EFFICIENT USE OF WEED CONTROL MEASURES. ON THE CONTACT INFORMATION AND RESOURCE PAGE THERE ARE A NUMBER OF SITES THAT HAVE EXCELLENT IDENTIFICATION KEYS BASED ON THESE CHARACTERISTICS. CONTACT INFORMATION AND RESOURCES THIS IS FOR GENERAL USE; REMEMBER TO USE ALL OTHER RESOURCES AVAILABLE TO EVALUATE THE IDENTIFICATION OF A WEED SPECIES. Disclaimer All links to external sites open in a new window. You may return to the University of Arkansas System Division of Agriculture web site by closing this window when you are finished. We do not guarantee the accuracy of the information, or the accessibility for people with disabilities listed at any external site. Links to commercial sites are provided for information and convenience only. Inclusion of sites does not imply University of Arkansas System Division of Agriculture's approval of their product or service to the exclusion of others that may be similar, nor does it guarantee or warrant the standard of the products or service offered. The mention of any commercial product in this web site does not imply its endorsement by the University of Arkansas System Division of Agriculture over other products not named, nor does the omission imply that they are not satisfactory.
WEED IDENTIFICATION GLOSSARY - A - Le ASEXUAL REPRODUCTION BULB RHIZOME ROOT STOLON TUBER COTYLEDON GROWTH HABIT DECUMBENT ERECT PROSTRATE ROSETTE GLABROUS JOINTING & BOLTING LEAF ARRANGEMENT ALTERNATE OPPOSITE ROSETTE WHORLED LEAF MORPHOLOGY GENERAL BLADE COMPOUND INTERNODE NODE SHAPE SIMPLE
WEED IDENTIFICATION GLOSSARY - Le - Z LEAF MORPHOLOGY DICOT LEAFLET OCREA PETIOLE STIPULE TENDRIL THORN (SPINE) LEAF MORPHOLOGY MONOCOT AURICLE COLLAR LIGULE SHEATH LEAF VENATION NET PARALLEL LIFE CYCLE PUBESCENCE ROOT ADVENTITIOUS BRACE TAP SEEDLING EMERGENCE EPIGEAL HYPOGEAL STEM STEM SHAPE TILLER
ASEXUAL PROPAGATION - A major area for the growth and identification of weed species is the natural production of vegetative plant structures that have the capacity to produce new plants. Asexual propagation is the best way to maintain some species. Many of these vegetative structures are modified stems and include structures produced below the soil line (bulbs, rhizomes, roots, and tubers) and above the soil (stolons). Many of these serve as food storage areas for the plant. True roots, although less prevalent, are also found in several wee species.
BULBS: consist of very short stems with closely packed leaves arranged in concentric circles around the stem. The leaves are swollen with stored food e.g. wild onion and wild garlic. A terminal bud will produce the flowering shoot and the lateral (axillary) buds will produce new plants.
RHIZOMES - are stems which grow horizontally under the ground. in some cases the underground stems are swollen with food reserves. The terminal bud turns upwards to produce the vegetative shoot. Examples below include Johnsongrass and sedge.
One type of asexual propagation is a true root system producing adventitious shoots. It is found in the nightshade (solanaceae) and the asteraceae family [typically in the thistle group]. New plants emerge from rootstocks buried below the soil surface.
STOLON - is a horizontal stem that can produce new adventitious roots. A term that is also used is a runner.
TUBERS - Are thick, underground stems that develop at the end of rhizomes. The tuber has all the parts of a normal stem, including nodes and internodes. Below is the production of tubers from a rhizome on a sedge plant.
COTYLEDON (SEED LEAVES): Function of this structure is primarily storage of reserves for use during germination; tissue will be photosynthetic with the duration of this function being variable based on the species. COTYLEDON SHAPES
GROWTH HABIT DECUMBENT : The term used to describe the growth of the stem when they are prostrate with leaves growing upwards.
GROWTH HABIT - ERECT The term used to describe the upright growth of the stem and leaves.
GROWTH HABIT PROSTRATE : The term used to describe the growth of the stem when they are flat on the ground.
GROWTH HABIT ROSETTE: The term used to describe the growth of the stem when the internodes are not elongated (compressed).
PUBESCENCE: Plants that have trichomes on any plant part (leaf, stem, petiole, etc.). These trichomes can be dense to sparse with the location being very specific within a weed species. GLABROUS: Without any trichomes.:
JOINTING A term used to describe the elongation of the internode in monocots; allows for a separation of the nodes of the plant. BOLTING - A term used to describe the elongation of the internode in dicots which typically have a rosette type of growth; allows for a separation of the nodes of the plant. Typical in biennials. NODE INTERNODE
LEAF ARRANGEMENT ALTERNATE: Has one leaf which emerges per node on the stem. LEAF ARRANGEMENT WHORLED: Has more than two leaves emerging from the same node on the stem. LEAF ARRANGEMENT OPPOSITE; Has two leaves which emerge per node on the stem.
LEAF BLADE A general term used to describe the part of the leaf that is photosynthetic.
COMPOUND LEAF A leaf that has multiple leaflets; the point of attachment to the stem is still a petiole but the leaflets are attached to a structure called a rachis. SIMPLE LEAF Has a single blade and is attached to the plant by a petiole.
NODES Are enlarged regions of stems that are generally solid and where leaves are attached; will also have axillary buds for continued vegetative and reproductive growth. INTERNODES - The region of a stem between two successive nodes. STIPULE - Is an appendage of the young leaf and is attached to the base of the petiole.
LEAF SHAPES
LEAFLET A term used to describe the individual blades on a compound leaf.
OCREA - A unique structure that we find in in some dicots. They are described as fused stipules that form a sheath around the stem. These are found within the circle with (a) curly dock (Rumex spp.) and (b) smartweeds (Polygonum spp.).
PETIOLE: The stalk that attaches a leaf blade to a stem of a simple leaf. Compound leave s point of attachment to the stem is still a petiole but the leaflets are attached to a structure called a rachis (the main axis of a compound leaf). PETIOLE
TENDRIL - Is a slender, coiling modified leaf or stem which aids in the support of the shoot system.
THORNS (SPINES) - Are found on various plant parts and are typically hard structures with sharp, stiff ends. The terms are used interchangeably, but thorns are structures typically derived from shoots, whereas spines typically develop from leaves.
ILLUSTRATIONS OF THE VARIOUS COMPONENT ASSOCIATED WITH THE COLLAR REGION IN A MONOCOT AND MAY INCLUDE THE LIGULE, AURICLE, AND THE SHEATH LIGULE LIGULE - is a structure on the inside of the collar. A ligule is either membranous, hairy or absent. AURICLE AURICLES - are claw like appendages found at the junction of the leaf blade and the leaf sheath. SHEATH TYPES OF SHEATHS
LIGULE AURICLE
SHEATHS - Are tubular extensions of a grass leaf that surrounds the stem. classifications are based on the general appearance and can be overlapping, split, or united.
NETTED-VEINED LEAVES These leaves have a few prominent veins from which a large number of minor veins arise.
PARALLEL-VEINED LEAVES- These leaves contain veins about equal in size and running parallel. Growth of grass leaves takes place by elongation near the base.
LIFE CYCLE ANNUALS- Plants that complete their entire life cycle (from seed to seed) in a single growing season. BIENNIALS- Require two growing seasons to complete their life cycle. Vegetative growth occurs during the first season (vernalization occurs during the winter), and flowering and fruiting occur in the second season. PERENNIALS- Have an indefinite life period based on species and environment. They differ from other classifications in that they do not cease growth after reproduction.
ROOTS, ADVENTITIOUS: Refers to roots arising from areas not related to the true root (product of the radicle). ROOT, TAP: The descending axis of a plant derived from the radicle.
ROOT, BRACE A type of adventitious root that grows from the stem above-ground and serves for support of the plant.
STEM- The main body of a plant, usually the ascending axis, whether above or below the ground in opposition to the descending axis or root. Stems, but not roots, produce nodes and axillary buds.
STEM SHAPE - Varies in plant types. The classifications include: round, triangular (typical of sedges, oval, and square (typical of the mint family.
TILLER (OR TO DESCIBE THE PROCESS IS TILLERING) - is the production of additional stems from the activity of the axillary buds.
ILLUSTRATION OF VARIOUS COTYLEDON SHAPES> Linear oblong lanceolate spatulate oval round ovate kidney butterfly RETURN
EMERGENCE TYPES In hypogeal germination, the epicotyl or plumule will grow and emerge above the soil surface. However, the cotyledons and the first node will remain below the soil surface. Typical of monocots and cool-season dicots. In epigeal emergence, we have the epicotyl, cotyledon, and the first node moving above the soil surface. Typical of most dicots. plumule coleoptile cotyledon First node hypocotyl
This is a link to the MP44 published by the UA/CES. This contains information on labeled herbicides in the state of Arkansas. This publication also contains information of resistance management, spray information and REIs. MP44 This is a link to the International Survey of Herbicide Resistant Weeds. This website contains current information on herbicide resistance weeds and their management. ISHRW These are links to several websites that have information on weed species identification. AgWeb Online Field Guide - Weeds University of Arkansas- Weed ID For further information or comments, please contact the following personnel: Cal Shumway, Agronomist Bob Scott, Weed Scientist COAT, Arkansas State University Lonoke Agricultural Center State University, AR 72467 Lonoke AR 72086 Email: cshumway@astate.edu Email: bscott@uaex.edu The University of Arkansas System Division of Agriculture offers all its Extension and Research programs to all eligible persons regardless of race, color, sex, gender identity, sexual orientation, national origin, religion, age, disability, marital or veteran status, genetic information, or any other legally protected status, and is an Affirmative Action/Equal Opportunity Employer."