Glossary Terms


a dry, 1-seeded fruit with a firm close-fitting outer coat that does not open by any regular dehiscence (the process of splitting open at maturity). All fruits (seeds) of the Smartweed and Composite Families are achenes.
knotweed, Prostrate Polygonum aviculare
ragweed, common Ambrosia artemisiifolia


a description of the shape of a leaf tip whose sides are somewhat concave and appear stretched out to a protracted point
knotweed, Japanese Polygonum cuspidatum
Dame's-rocket Hesperis matronalis.


placed singly at different heights on the stem or axis
Wormseed mustard Crysimum cheirantheoides; any arrangement of leaves or other parts that are not strictly opposite or whorled.


a plant which completes its life cycle in one growing season. Compare with winter annual, biennial, perennial.


the enlarged outer portion of the stamen that produces pollen.


an appendage near the lower part of a leaf blade or petal; it may be pointed
Quack grass Agropyron repens
Stinkweed Thlaspi arvense or rounded and shaped like the lobe of a human ear
sow-thistle, spiny annual Sonchus asper.


a bristle-like part or appendage, usually needle-shaped
Wild oats Avena fatua


the upper angle formed by the junction of a leaf or branch with the stem.


Offset a short side shoot arising at the base of a stem or from a root crown.


a plant which germinates in the spring, producing a rosette of leaves and remaining vegetative during the first summer; overwinters as a rosette; bolts (sends up a flowering stalk) during the second summer; sets seed; and dies at the end of the second growing season. Compare with annual, winter annual, perennial.

Biological Control

Involves establishing a self-perpetuating population of a natural enemy from elsewhere with the intent of providing sustained weed suppression. It is particularly applicable to introduced weeds that have formed stable populations on uncultivated land. It relies on the agent, which usually an insect, increasing to suppress increases in the weed population. The control is slow to take effect, up to 20 years, but in the right situation it is the most cost effective and environmentally friendly means of weed control.


Biopesticides are pesticides derived from natural materials such as animals, plants, bacteria, and certain minerals. Acetic acid (Vinegar) and corn gluten meal are examples of two biopesticides that suppress or control certain weed species.


the expanded part of a leaf or petal.


in this site, it is used only in the sense of a fine, powdery coating on leaves, stems, etc. Also see glaucous. (When referring to a flower, the word blossom is used.)


a flower.


a leaf that is much reduced; particularly the small or scale-like leaves immediately below each flower in a flower cluster
Yellow evening primrose Oenothera biennis
Heal-all Prunella vulgaris L., or associated with the inflorescence.
carrot, Wild Daucus Carota
water-hemlock, Spotted cicuta maculata


the sepals of a flower; the outermost series of flower parts; it is usually, but not always, green and leaf-like in texture.


fringed with fine hairs along the edge or margin.
Green foxtail Setaria viridis


partly or wholly surrounding the stem.
Stinkweed Thlaspi arvense
sow-thistle, spiny annual Sonchus asper


divided to or almost to the midrib, as a palmately cleft leaf
buttercup, tall Ranunculus acris
ragweed, giant Ambrosia trifida or pinnately cleft leaf.
Dandelion Taraxacum officinale


the junction between leaf blade and leaf sheath in grass and sedge leaves.


made up of two or more similar parts, united into one whole. A compound leaf is divided into several separate leaflets. A compound unbel is made up of several simple umbels.


the petals of a flower; an inner series of flower parts, usually between sepals and stamens; it is usually white or coloured, and usually not leaf-like in texture.


a seed leaf. These tiny leaves are present in the embryo in the seed. In most broad-leaved dicotyledonous plants, they emerge when the seed germinates. They are the first green leaves of these seedlings and are always an opposite pair.


the part of the stem at the surface of the ground. Also, specialized appendages on the corolla in a flower as the hoods and horns in Milkweed
milkweed, Common Asclepias syriaca, or the trumpet in the cultivated daffodil.


the stem of grasses and bamboos, usually hollow except at the swollen nodes.


a specialized cup-like structure that encloses one or more tiny flowers in the Spurge Family.


an inflorescence in which virtually every stem and branch ends in a flower, and does not have a well-defined central axis
Stichwort, Grass-leaved Stellaria graminea
White cockle Silene alba
Bladder Campion Silene vulgaris . The central or uppermost flower usually blossoms first.


with sharp teeth that are perpendicular to the margin; the two sides of each tooth being of about equal length and having the same slope.


with 2n (2 complete sets of) chromosomes per cell; one complete set having come from each parent.


floret a tubula flower in the central part of the flower head of many members of the Composite Family
daisy, Ox-eye Chrysantheum leucanthemum, as distinguished from a ray floret.


separated to very near the base.
buttercup, tall Ranunculus acris


with a continuous margin, not in any way toothed or otherwise indented or divided.
Bladder Campion Silene vulgaris [
Dogbane, spreading Apocynum androsaemifolium

Environmental Impact Quotient (EIQ)

The EIQ is designed to provide growers and other decision makers with one number that indicates the magnitude of relative risk. The EIQ was developed by Kovach and others from Ohio State University to estimate the risk to farm workers, consumers, and the environment of pesticide active ingredients. The toxicology, as well as persistence and movement in the environment were used to calculate the EIQ. In the environmental impact of a pesticide product is determined by multiplying the application dose (kg ai/ha) by the EIQ value for the active ingredient. Thus, a higher environmental impact value indicates a greater risk compared to another product. By using lower herbicide rates and/or safer products, the environmental impact of weed control may be reduced.


the stalk of the stamen.


a small flower, especially the individual flowers in a flower head of the Composite Family
daisy, Ox-eye Chrysantheum leucanthemum; or the flower plus its two enclosing bracts, the lemma and palea, in the Grass Family.
Quack grass Agropyron repens


the leaf blade of a fern, whether single or much divided.


a mature ovary with or without associated parts. In the botanical sense, it is not restricted to something sweet and juicy but includes all kinds of berries
buckthorn, European Rhamnus cathartica
nightshade, Climbing Solanum dulcamara L., dry seedpods
mustard, wild Sinapis arvensis
Velvetleaf Abutilon theophrasti
nightshade, Climbing Solanum dulcamara L., spiny burs
Sandbur Cenchrus longispinus
Jimsonweed Datura stramonium, and single-seeded achenes
knotweed, Prostrate Polygonum aviculare
buttercup, tall Ranunculus acris
buttercup, Creeping Ranunculus repens
ragweed, common Ambrosia artemisiifolia


covered with a powdery whitish substance or bloom that is easily rubbed off.


the absorbing organs (often root-like) of parasitic plants.


the floral cup or tube in a flower to which are attached the sepals, petals and stamens.


the flowering portion of a plant.


the part of a stem or rhizome between any two nodes.
Quack grass Agropyron repens
knotweed, Japanese Polygonum cuspidatum


one or more whorls of small leaves or bracts immediately underneath a flower, flower cluster or umbel, or surrounding a flower head.
Flower-of-an-hour Hibiscus trionum
daisy, Ox-eye Chrysantheum leucanthemum


lance-shaped; much longer than broad, and narrowed or pointed toward the tip

Leaf Axil

the upper angle between the stalk or blade of a leaf and the stem.

Leaf Sheath

the basal portion of a leaf that surrounds the stem, especially in grasses and sedges; the portion of a leaf between the stem node and leaf collar.


one part of a compound leaf.
Vetch, tufted Vicia cracca
Poison ivy Toxicodendron radicans


a flat membrane or band of hair arising from the inner surface of the leaf sheath at its junction with the leaf blade.
Green foxtail Setaria viridis is an example of a species that has a hariy ligule and
Large crab grass Digitaria sanguinalis is an example of a species with a membranous ligule


the main or central rib or large vein of a leaf or leaf-like part; appears to be a continuation of the petiole.


the joint of a stem or rhizome; that portion of a stem to which the leaf is attached
Quack grass Agropyron repens
Lady's thumb Polygonum persicaria
water-hemlock, Spotted cicuta maculata, and at which axillary buds and branches are produced.


a membranous or somewhat leaf-like tube surrounding the stem above each node in the Buckwheat or Smartweed Family.
Broad-leaved Dock Rumex obtusifolius
Lady's thumb Polygonum persicaria


placed two at a node; on opposing sides of a stem, immediately across from each other.
White cockle Silene alba
Motherwort Leonurus cardiaca


the lower part of the pistil; it contains the ovules that later become the seeds.


the tiny structure inside an ovary that develops into a seed after fertilization.


the arrangement of leaflets, or of lobes, divisions, ribs or veins in a leaf or petal in which all of these units arise from almost the same point, as fingers from the palm of a hand.
mallow, Common Malva neglecta
ragweed, giant Ambrosia trifida


a type of inflorescence that usually has a central axis and many branches that are them-selves more or less rebranched.
Wild oats Avena fatua
Witch grass Panicum capillare


the specialized calyx of members of the Composite Family; may consist of hairs, plumes, bristles or scales.
Goat's-beard Tragopogon dubius


cut or cleft, but not quite to the midrib or base.


stalk of a single flower or of one flower in a cluster.


the stalk of a cluster of flowers, or of a flower head.
daisy, Ox-eye Chrysantheum leucanthemum


a plant that lives through three or more growing seasons. Compare with annual, winter annual, biennial.


a collective term for the calyx (sepals) plus corolla (petals).


stalk of one leaf.


the arrangement of leaflets, or of lobes, divisions or veins in a leaf or petal in which these units are arranged on each side of an elongated, central axis.
Vetch, tufted Vicia cracca
Black-eyed susan Rudbeckia hirta


the female part of a flower, consisting of stigma, style and ovary; it contains the ovules and develops into the fruit which contains the seeds.


having one or more pistils but no stamens; female.

Power Ranking

Every weed species within the database contains a power ranking. The power ranking considers two components, how abundant and how difficult the species is to control in corn and soybeans. These initial rankings have originated from informal grower and crop advisor surveys whereby they where asked to prioritize a number of weed species in terms of management importance. In the future more formal surveys, along with feedback through will determine power rankings for weeds on a yearly basis.


an inflorescence composed of several to many flowers, and later fruits or seedpods, each with a distinct pedicel, arranged along a central axis which continues to elongate throughout the flowering period
Yellow rocket Barbarea vulgaris
Stinkweed Thlaspi arvense. The lower flower blossoms first.


the central axis of a spikelet, particularly in the grasses and sedges; the axis to which the florets are attached
Quack grass Agropyron repens.


the central axis of either a pinnate leaf or of an inflorescence.
Quack grass Agropyron repens
Yellow avens Geum aleppicum
Vetch, tufted Vicia cracca

Radical Leaf

a leaf that arises from an underground stem (rhizome) and whose petiole emerges directly from the soil surface.
bellflower, Creeping Campanula rapuncloides


one of several branches of an umbel or similar inflorescence
water-hemlock, Spotted cicuta maculata

Ray Floret

the outer florets in the flower head of some members of the Composite Family, as distinguished from a disk floret.
daisy, Ox-eye Chrysantheum leucanthemum


an underground stem, usually horizontal.
Quack grass Agropyron repens
knotweed, Japanese Polygonum cuspidatum
Goutweed Aegopodium podagraire


a circular cluster, with the parts spreading outward like spokes of a wheel.
Yellow rocket Barbarea vulgaris
thistle, Nodding carduus nutans


one of the separate parts of a calyx; usually the outermost part of a flower, and usually (but not always) green.


a membranous partition.


with sharp teeth that point forward along the margin; one side of each tooth being longer than the other.
Rough cinquefoil Potentilla norvegica
Catnip Nepeta cataria
Beggarticks, Nodding Bidens cernua


without a stalk; said of a leaf in which the leaf blade has no petiole but is attached directly to the stem
Bladder Campion Silene vulgaris
Stinkweed Thlaspi arvense, or of a flower that has virtually no pedicel but appears to be attached directly to the stem
mullein, Common Verbascum thapsus
Broad-leaved plantain Plantago major.


the relatively short fruit of certain members of the Mustard Family, usually not more than twice as long as wide.
Stinkweed Thlaspi arvense


the relatively long fruit of certain members of the Mustard Family, usually at least four times longer than wide.
mustard, wild Sinapis arvensis
Wormseed mustard Crysimum cheirantheoides


a distinct space between two lobes, as on a leaf blade .


a large bract enclosing an inflorescence, at least when young; may be papery in texture and white or brownish more leaf-like and green, white or highly coloured, as in the woodland wild flower, Jack-in-the-pulpit.


an inflorescence with sessile flowers, and later fruits, arranged along a central axis. The lower flowers blossom first.
Quack grass Agropyron repens
Lamb's-quarters Chenopodium album
Broad-leaved plantain Plantago major


the basic unit of a grass or sedge inflorescence
Quack grass Agropyron repens . It contains the flower(s) and seed(s) that are enclosed by the chaffÕ (by the lemma, palea and glumes).


the stem or supporting structure of any organ, as the petiole of a leaf, the peduncle of an inflorescence, the pedicel of a flower, or the filament of a stamen.


the male or pollen-bearing part of a flower, consisting of an anther and a filament.


having stamens but not pistils; male.


the part of the pistil that receives the pollen; usually the uppermost or outermost part of a pistil.


the stalk of a pistil, between the bottom of the pistil and the top of the receptacle (found inside the flower); not to be confused with the pedicel that occurs below the receptacle to which the petals and sepals are usually attached.


having stipules.


an appendage at the junction of the leaf petiole and stem
Yellow avens Geum aleppicum
Violet, Field Viola arvensis; usually occur in pairs, one on each side of the petiole, and may be attached to the petiole or to the node of the stem.


a horizontal stem at or slightly below the surface of the ground, and gives rise to a new plant at its tip.


the more or less elongated part of the pistil between the ovary and the stigma.


juicy or fleshy, often brittle.


the primary root; usually larger than the branch roots; and usually present in most annual and biennial plants.


the slender, twining or clasping structure at the ends of some compound leaves or coming directly from the stem
Vetch, tufted Vicia cracca
Wild cucumber Echinocystis lobata.


with 4n (4 complete sets of) chromosomes per cell.


a thickened, short underground stem or root serving as a storage organ containing reserve food. The common potato that we eat is a tuber.
water-hemlock, Spotted cicuta maculata


a spherical, rounded or flat-topped inflorescence with the pedicels of the individual flowers, or the peduncles of the umbellets, arising from approximately the same point.
carrot, Wild Daucus Carota


a secondary umbel within a compound umbel.
Water parsnip Sium suave
water-hemlock, Spotted cicuta maculata


of one sex; having only stamens or only one or more pistils in each flower.
ragweed, common Ambrosia artemisiifolia


three or more leaves or flowers at one node; with the parts encircling the stem and pointing outward like the spokes of a wheel.
Corn spurry Spergula arvensis

Winter Annual

a plant that germinates in the fall; usually overwinters in the rosette stage; flowers and sets seed the following spring; and dies in the summer.