Bulbil

An organ used for vegetative propagation by some creeping perennials. Includes wild garlic. Bulbils are produced in the inflorescence, and can be carried much further from the plant than bulbs.

Direct interference

A contributing factor of interference. The negative effect that one plant exerts on another by producing chemical substances. Allelopathic toxins can be released by: exudation from roots, washing from leaves, volatile gases, and decaying plant parts. It is difficult to prove whether a plant is allelopathic or not, because we don't know all the weeds that use allelopathic compounds. Some aggressive perennials release toxic compounds from decaying dead material, which can be a problem if susceptible crops are planted on a site that was previously heavily infested by these weeds. Evolved to help plants reduce competition for resources. Gives advantage to some weeds.

Agamospermy

Production of seeds without fertilization. A form of asexual reproduction. There are several types. The flower may require contact with pollen, but there is no exchange of gametes. The seed has the same genome as the mother plant; it is a clone. Some plants are evolved to have apomixis more often than others. Occurs in cypress, citrus crops, and many arctic species. Can cause problems for plant breeders.

Family Brassicaceae. When grown under low red/far red light ratio, similar to shade, it has a narrow growth habit compared to a plant grown under normal light conditions, even when light intensity is the same.

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Clonal reproduction

Includes apomixis and vegetative reproduction (rhizomes, plagiotropic roots, stolons, tubers, bulbs). The plants benefit from genetic stability of clones: plants with best adaptations to the environment remain in place. A simpler way to reproduce that does not require the same energy investment as sexual reproduction, such as elaborate flowers and specialized organs. Represents an additional way to reproduce that may supplement seed production. May allow some species to reproduce and multiply under sub-optimal conditions. Some species may have both sexual and asexual reproduction under optimal conditions, but at the margin of its natural distribution range, where conditions are sub-optimal, it has only asexual reproduction. Even if sexual reproduction is impaired, asexual reproduction may still take place. A disadvantage is that there is no exchange of genetic material. Does not increase genetic diversity, the basis for natural selection. A major environmental change, such as herbicide application, may negatively affect the whole population.

Musa sp.

Family Musaceae. Has vegetative propagation with ratoons.

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Bidens sp.

Family Asteraceae. The seeds have little appendages which look like legs, making them resemble ticks.

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Medicago lupulina

Family Fabaceae. A legume. The first true leaf is an oval unifoliate. Later leaves are trifoliate, with diamond-shaped leaflets. The centre leaf has a petiole whereas the other two do not. Has a prostrate growth habit. Found in turf and pastures. Has good qualities as feed for livestock. Adapted to less disturbed environments. Has clusters of small yellow flowers. The name comes from its black seed pods. Can look similar to common yellow woodsorrel.

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Plantago major

Family Plantaginaceae. A stationary perennial. Has vegetative propagation with a shallow underground shoot, and ratoons. Has a short vertical stem.

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Rhamnus sp.

Family Rhamnaceae. An invasive species.

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Ranunculus bulbosus

Family Ranunculaceae. Has vegetative propagation with corms. Found in Ontario and Europe.

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Cirsium vulgare

Family Asteraceae. A perennial. Has a taproot.

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Cirsium arvense

Family Asteraceae. A creeping perennial. A weed found in North America and Australia which was introduced from Europe. Moved from France to Quebec, then spread across the continent to California. Has vegetative propagation with horizontal roots, which can go very deep.

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Brassica rapa

Family Brassicaceae. As a volunteer, it is the second most common weed in Western Canada.

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"Goose foot"

A family of plants. Includes common lamb's quarters, fig-leaved goosefoot, spreading atriplex, kochia, sugarbeet, quinoa, beets, and spinach. Leaves can resemble goose feet. Evolved to live in saline environments, such as sea coasts, or areas with little irrigation. Salts are pumped into the trichomes, to exude it from cells.

Climax community

Stability

The seventh and final stage of the succession process. There is a stable climax community, which is usually a wooded forest. It can take 75 - 100 years to reach climax.

Xanthium sp.

Family Asteraceae. Has hooks on the seeds to aid with dispersal, by sticking to animals' fur and peoples' clothes.

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Tussilago farfara

Family Asteraceae. A creeping perennial. Has vegetative propagation with rhizomes.

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Arctium minus

Family Asteracea. Has hooks on the seed to aid with dispersal, by sticking to animals' fur and peoples' clothes. The hooks were the inspiration for the invention of Velcro.

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Stellaria media

Family Caryophyllaceae. A winter and spring annual. Common in turf and winter crops. Has vegetative propagation with rhizomes. It looks fragile, but can be a persistent weed. Leaves are ovate, with a pointed tip, arranged oppositely. Prostrate growth habit, forming mats. Flowers are small. Petals are bifid, with 5 petals appearing like 10. Stem is hairy on one side only, with sides alternating by node. Can appear similar to scarlet pimpernel.

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Chenopodium album

Fat hen

Family Chenopodiaceae. Closely related to quinoa and spinach. Name comes from when it grew in lamb's pastures. The tenth worst weed worldwide. Very common in all crops, anywhere soil is disturbed. A pioneer species; exploits resources quickly. Its WUE is 658; this poor water efficiency wastes water from the available pool, thus reducing water availability for neighboring plants. Has luxury consumption of nitrogen. Edible, and tastes like spinach. Has an erect growth habit. Produces salt bubbles on its surface, giving it a white sheen with a mealy texture. Leaves are alternating. Has small, green flowers. Seeds can survive for 1,700 years in the seedbank. Seeds must be near the surface to germinate. Can appear similar to fig-leaved goosefoot and spreading atriplex. 

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Malva neglecta

Family Malvaceae. A perennial. Can have a deep taproot. If it has the space to, it will take on a bushy growth habit. If it is mowed down or cut, it grows in a prostrate growth habit. Leaves are kidney-shaped with irregular, jagged indentations. Flowers are small, with five petals, white with pink stripes. Some ornamental varieties have bigger flowers.

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Asclepias syriaca

Family Apocynaceae. Has vegetative propagation with rhizomes, which can reach 2 feet deep. Can produce latex and silk. Seeds can survive for 3 years in the seedbank. Has feathery appendages on the seeds to aid with dispersal on the wind. It was removed from the list of noxious weeds because it is a food source for the Monarch butterfly.

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Verbascum thapsus

Devil's tobacco

Family Scrophulariaceae. A biennial weed, capable of very early start in the spring. It can grow back after a fire. Highly competitive. An early successional species. Can grow to be very tall. Has fuzzy leaves.

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Oxalis stricta

Family Oxalidaceae. It is edible, and has a sour taste. It contains oxalic acid, which is why it is bad to eat too much of it. Leaves are trifoliate, with heart-shaped leaflets. Flowers occur singly, and have 5 petals. Sometimes leaves are mistakenly sold as clover shamrocks near St. Patrick's Day. Can appear similar to black medick.

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Indirect interference

The fourth stage of the succession process. A contributing factor of interference. The negative relationship between two species that is due to the exploitation of resources that are present in limited supply, and are needed for growth and development. Involves various species competing for resources and space. Some plants may grow faster than others. Competition occurs for three types of resources: water, nutrients, and light. The outcome of competition is decided by: weed density, weed distribution, spacing, time, and weed species. Competition for different types of resources is interrelated, because lack of one resource can diminish a plant's ability to acquire other resources.

Zea mays

Family Poaceae. A tall, dense crop. Early control of weeds allows the plants to produce enough foliage that they shade the soil, preventing further weed germination. Can experience nitrogen toxicity. Volunteer corn may be the main grass weed in Ontario, according to one Ridgetown professor. If it is artificially made to self-pollinate for multiple generations, the plants become inbred; they are short and low-yielding. Crossing two inbred lines produces a hybrid plant.

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Digitaria sp.

Family Poaceae. An annual. Has vegetative propagation with rhizomes.

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Vaccinium macrocarpon

Family Ericaceae. Grown in Muskoka, in flooded fields. Can experience aquatic weeds.

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Ranunculus repens

Family Ranunculaceae. A creeping perennial. Has vegetative propagation with stolons. Invades pastures. Can be toxic to horses and cattle. Forms a crown of trifoliate leaves. Can appear similar to tall buttercup, but it has more lateral branching. 

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Glechoma hederacea

Family Lamiaceae. A creeping perennial capable of nutrient foraging.

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Wandering perennial

A perennial which has vegetative multiplication due to abscission or rotting. This is important even if there is no cultivation. It spreads out sideways. May have spontaneous dispersal by aerial bulblets, stolons, rhizomes, and roots. Many have the capacity for nutrient foraging.

Rumex crispus

Family Polygonaeae. A stationary perennial with a taproot. Can develop shoots from only the upper part of the taproot. Found near fences, in pastures, and no-till systems. Likes moist areas, such as near streams, but can grow elsewhere. Has long leaves with wavy edges and a leathery texture. There are red dots on the leaves. Has small greenish flowers. Fruits have floaters of trapped air, allowing them to float on water, and be carried by wind.

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Family Asteraceae. Has vegetative propagation with corms.

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Taraxacum sp.

Family Asteraceae. A stationary perennial. Has vegetative propagation with a vertical taproot. Can develop shoots from any part of the taproot when it is cut. Has a showy flower, despite reproducing mostly from apomixis. There are only a few races of dandelions, which are fixed clones. Has feathery appendages on the seeds (the pappus) to aid with dispersal on the wind, and may help seeds grip to animals. In one experiment, seeds were planted in various positions, and germination rates measured. The seeds germinated very poorly when planted upside-down; the pappus must have another function in ensuring the seed lands in the right orientation. 

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Broadleaf

A grouping of plants.

Nudation

The first stage of the succession process. Development of a bare site. Anything which kills vegetation. Can be a volcanic eruption, filling up of a lake, forest fire, tillage of a field, or use of herbicides.

Cuscuta sp.

Family Convolvulaceae. A parasitic plant. Almost like a disease. A noxious weed under the Weed Control Act. Not very common in Ontario. Grows near rivers. It is on the list of noxious weeds on the Ontario Seed Act. Can be a problem in alfalfa. It is more problematic in other countries, especially warm, dry climates. It sucks moisture from the host plant.

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Intermediate species

Species which are found during the middle of the succession process, after pioneer species. Includes grasses, shrubs, pines, oak, and hickory. In abandoned agricultural fields, there are grasses and bushes. Includes biennial and perennial species. Mostly herbaceous. Found in no-till systems, pastures, turf, and orchards, where there is reduced disturbance.

Solanum ptychanthum

Family Solanaceae. A weed which has poisonous berries. Can affect humans, livestock, and pets.

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Convolvulus arvensis

Family Convolvulaceae. An early successional species. A creeping perennial. A noxious weed under the Weed Control Act. Has vegetative propagation with roots and rhizomes. It will return even after it is pulled out. It is able to climb on other plants, and position its leaves more favourably for competition for light. Can look similar to wild buckwheat, but has a more variable leaf shape.

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Viola arvensis

Family Violaceae. Fruits have forced dehiscence.

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Chenopodium ficifolium

Family Chenopodiaceae. Leaves resemble fig leaves; there are indentations on the sides. Other than leaf shape, it appears similar to common lamb's quarters.

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Alopecurus sp.

Family Poaceae. The third most common weed in Western Canada.

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Hordeum jubatum

Family Poaceae. A stationary perennial with shallow subterranean stems. Grows in clumps.

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Setaria faberi

Family Poaceae. The ligule is ciliated, and the leaf blade is hairy on one side.

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Heracleum mantegazzianum

Family Apiaceae. A weed that can cause skin irritation by making the skin sensitive to UV rays.

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Ambrosia trifida

Family Asteraceae. Can grow to be fairly tall. Produces allergenic pollen. One grad student helped grow a plant in the greenhouse. He gave it a large container and plenty of fertilizer. It grew all the way to the greenhouse roof! The pollen from the plant had to be scooped off the ground, there was so much of it.

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Amaranthus powellii

Powell amaranth

Family Amaranthaceae. Stem is reddish at the top, with few hairs. There are tepals in the flower. Can appear similar to redroot pigweed, but the sheen on the leaf is shinier, though this can depend on soil nutrition. The inflorescence is less compact than in redroot pigweed, and more finger-shaped.

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Geographical dispersal

When seeds travel a short or long distance from the mother plant. Seeds may be carried by wind, water, or animals.

Equisetum sp.

Scourbrush

Family Equisetaceae. A creeping perennial. Has vegetative propagation with rhizomes, forming a dense rhizome system that can compete with crops underground. Looks like sticks, with no leaves.

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Competition

The negative relationship between two plants. The result of two phenomena: competition and allelopathy. It is the sum of these two factors. It is difficult to distinguish the contribution of each component to the overall outcome of interference. The effects of the two factors are difficult to separate experimentally.

Ambrosia artemisiifolia

Family Asteraceae. A noxious weed under the Weed Control Act.

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Quarantine

The second phase of eradication. Ensuring there is no dispersal of the weed. Species disperse mostly by human means. For Striga in the USA, there was limitation on movement of soil, compost, crops, produce, and machinery such as implements, harvesters, tractors, and various tools.

Control of weeds

The third phase of eradication. For Striga in the USA, plants were eliminated as they were found, to prevent seed set. Herbicides were used in crops. Attempts at controlling the seedbank were made. Deaths in the seedbank was accelerated by triggering suicide germination without a host using ethylene, or accelerating mortality with the fumigant methyl bromide.

Aegilops sp.

Family Poaceae. The seeds stick to the rachis and shatter. It is hard to clean its seeds from crop seeds.

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1674 - 1741

Lived in England, as a owner of a farm, who had people working for him. He traveled Europe, and became concerned that his farm was inefficient, so he invented the seed drill. It was unknown at the time whether weeds had any effect on crops, and Tull believed that they did. Jethro Tull is also the name of a band from the 1970s.

Impatiens capensis

Family Balsaminaceae. The seed pod builds up tension as it develops, then when cells disintegrate, suddenly seeds are flung away from the plant.

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Kochia scoparia

Tumbleweed

Family Chenopodiaceae. A bad weed in Western Canada and USA. Less common in Ontario, where its seeds may be found in alfalfa produced in Western Canada. The seeds are similar in size and shape to those of alfalfa, and can be difficult to clean out. Found on roadsides in Mexico and Arizona. Has resistance to many herbicides. Was once used as an ornamental. Seedlings have hairy leaves that grow in a rosette. Old and young leaves appear the same: narrow, with a smooth edge. The stem is ribbed, like in beets. Has a bushy and branchy growth habit. The plant forms into a ball shape, and as it matures, the base of the stem breaks. The plant rolls around, dispersing seeds as it tumbles. Sometimes tracks of seedlings can be seen, where a kochia plant has blown by.

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Persicaria maculosa

Family Polygonaceae. An annual. One of the most common weeds worldwide. Found right after disturbances. There is a triangular or circular print of darker green on the leaf, like a "lady's thumb"; the spot may have to do with heat dispersal. Ochrea are smooth and hairless, with a few hairs at the tip. Not an elegant-looking plant; has a loose growth habit.

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Lactuca sativa

Family Asteraceae. A delicate crop. It is slow-growing, and has a small root zone. Not a good competitor.

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Apera spica-venti

Family Poaceae. A weed that was found in Norfolk County in 1976. Believed to have been introduced with rye brought from Europe.

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Order Santales. A parasitic plant.

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Vigna radiata

Family Fabaceae. Well documented as having a high swelling rate during seed imbibition. Some seeds were able to lift a beaker of sand while imbibing water.

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Sinapis sp.

Family Brassicaceae. A weed found in North America and Australia which was introduced from Europe. Moved from France to Quebec, then across the continent to California. A pioneer species. Cotyledons are kidney-shaped. Leaves at the bottom of the plant are longer and rounder than leaves near the tip of the plant, which are pointed. One plant germinated in July, and then flowered with only two leaves; has high plasticity.

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Cyperus sp.

Family Cyperaceae. A monocot, but not a grass. A creeping perennial. Has vegetative propagation with tubers. Can tower over lettuce. Can be a harmful competitor. Grown in some countries for its highly nutritious tubers, which may be called "nutlets".

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Allium cepa

Family Amaryllidaceae. Has vegetative propagation with bulbs.

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Leucanthemum vulgare

Family Asteraceae. A dicot. A stationary perennial which uses a shallow, oblique subterranean perennating stem.

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Family Poaceae. A tall grass which is an emergent weed, growing in wet ditches. It grows from the tropics to the arctic. Pulling it out makes no difference because it is a perennial. Herbicides such as RoundUP may be used on it, though there is risk of contaminating the water.

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Amaranthus sp.

Family Amaranthaceae. A pioneer species. Can grow very fast. Produces a canopy in 8 days, becoming a problem. Can appear similar to three-seeded mercury. One grower had it growing in strips in his field, as though it had been planted artificially; seeds had fallen off an uncleaned combine brought in from the USA. Some Jamaican species are grown as a crop, similar to amaranth.

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Ananas comosus

Family Bromeliaceae. Has vegetative propagation with ratoons, which can form after harvest.

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Ruderal species

Species which are found early in the succession process, right after a disturbance. Includes annual plants, and perennial grasses and dicots. Generally annual, and short-lived. Adapted for sudden release of nutrients in the environment, such as after a fire. Exploit environment resources quickly. Have high plasticity. Can live in short-term openings in the land, such as flood plains. May appear every 3 - 5 years.

Toxicodendron radicans

Family Anacardiaceae. A weed that can cause skin irritation. Leaf oils cause an allergic reaction on the skin, leading to itchy blisters. Takes 3 - 4 days for symptoms to develop. Scratching makes it worse. Grows as a vine. Leaves are trifolaite, variable in shape, with irregular indentations. The two leaflets to the sides may be asymmetrical, and the centre leaflet has a longer petiole.

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"Many knees"

A family of plants. Has characteristically swollen nodes with ochrea. Includes curled dock, lady's thumb, prostrate knotweed, and wild buckwheat.

Euphorbia pulcherrima

Family Euphorbiaceae. It is very sensitive to daylength, requiring short days (long nights) to flower. In Ontario, to speed up the flowering process in time for Christmas, greenhouses use curtains to block out light. Even one flash of light can ruin the effect. Grows as a weed in New Zealand.

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Solanum tuberosum

Family Solanaceae. Has vegetative propagation with tubers as well as rhizomes, which are called stolons. Daylength and biomass triggers growth of tubers. The eyes are the nodes on the tuber, with meristems that can sprout to form a new plant.

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Panicum miliaceum

Family Poaceae. A C4 weed. Its WUE is 267.

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Polygonum aviculare

Family Polygonaceae. An annual. Found on turf and roadsides. Can tolerate stress, including a lot of trampling. Found in areas where there is a lot of foot traffic, such as on the edges of paths cutting through grass fields. Has a branchy, prostrate growth habit. Can have a more upright growth habit when found in cereal fields. Has a fibrous stem. Leaves are small and bluish. Small flowers form in axils, white, sometimes pink. It is less competitive with higher rates of nitrogen fertilizers.

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Cyperus rotundus

Family Cyperaceae. Has vegetative propagation with tubers. The tubers look like tiny potatoes, and can have up to six nodes.

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Portulaca oleracea

Family Portulacaceae. A C4 plant. It is edible, and eaten in salads and stew as a vegetable. High in minerals and vitamins. It is grown as a crop in the Mediterranean. May be used as an ornamental; wild plants have yellow flowers. It is adapted to warm, dry conditions. Can be a problem in strawberries, because it has late germination. Has a mostly prostrate growth habit, growing close to the soil. Can form thick mats. Has an extensive root system, in order to find water in moisture-limited conditions. The stem can sometimes appear red. Leaves arranged oppositely (two per node). Leaves are smooth and succulent; the plant uses them as a moisture reserve. It is a good system for studying shade avoidance response, because of its prostrate and branchy growth habit; you can watch where the plants will "crawl". It will grow away from green plastic objects, but not plastic objects of other colours.

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Elytrigia repens

Family Poaceae. A creeping perennial. Found in cooler areas around the world. Has vegetative propagation with rhizomes. Its rhizomes can reduce soil erosion. An aggressive weed. Releases toxic compounds from decaying dead material. Residues slow growth of alfalfa and clover, and reduce nodulation.

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Ambrosia sp.

Family Asteraceae. Many people are allergic to its pollen. The economic threshold is one plant per square metre, which causes over 20% yield loss.

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Light quality

The ratio of red photons to far red photons in light. Controls the levels of phytochrome types (Pr and Pfr), thus affecting various physiological processes in plants. Can affect leaf expansion, chloroplast development, stem elongation, root development, flowering, tillering, and apical dominance. In low R/FR light there is reduced lateral branching. Enables plants to distinguish between shade of a plant, and that of a non-plant object. Sunlight has high quality because it is red enriched with a high R/FR of about 1.2. When light passes through or is reflected off a plant canopy, some red light is absorbed for photosynthesis, but far red light is not used. Transmitted or reflected light has a lower quality, with a R/FR of 0.5 - 0.75. The low quality light which a  plant reflects is a function of the distance from the plant.

Amaranthus retroflexus

Family Amaranthaceae. Hairs are curled downwards. Leaves in seedlings have notches at the tips. Has diamond shaped leaves. Flowers are green, in a spiny inflorescence which hurts to touch. Similar-looking to other pigweeds. Can appear similar to nightshade. Its WUE is 305. This excellent water efficiency enables it to maintain growth even when water supply is becoming depleted.

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Oryza sativa

Family Poaceae. There were some attempts to grow rice in flooded fields in Ontario, but it didn't work well. Flooded rice can experience aquatic weeds.

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Lolium sp.

Family Poaceae. A turf and forage crop. Can be a competitive weed in wheat and other grains. Has cross-pollination. Seeds live for 4 years; if you can prevent recruitment of seeds for this amount of time, you can eradicate it. Grown in England and the Mediterranean. Important in Australia.

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Agnalis arvensis

Family Primulaceae. The stem is not hairy. There are black dots on the leaf underside. Flowers are red with 5 petals. Appears similar to common chickweed, but has darker green leaves. Scarlet Pimpernel is also the name of a superhero from the 18th century.

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Photomorphogenesis

Light affecting the shape of a plant. A response that a plant has to being in low R/FR light, such as when in the shade of a canopy. There are longer internodes, smaller leaves, and less roots. The plant is trying to become taller to avoid shading. Chloroplasts appear more yellow. Also occurs in plants which perceive light alteration coming from the sides, indicating that it is a response that also helps plants avoid competition. Two plants side by side, not shading each other, can cause shade avoidance response due to reflected light.

Capsella bursa-pastoris

Family Brassicaceae. A biennial. Early leaves are spoon-shaped, but then leaves that form later are a completely different shape, with many deep lobes. Texture of leaves is coarse and sandpapery, because the hairs are 5-pointed, branched like small stars; they are small and hard to see. Seed pods have a triangular shape with a notch at the tip. The name comes from when shepherds used purses made from the scrotums of rams, which resemble the triangular seed pods. Has small seeds, which struggle to emerge when planted 2 cm deep.

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Argentina anserina

Family Rosaceae. A creeping perennial. Has vegetative propagation with stolons.

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Glycine max

Family Fabaceae. A self-pollinating plant. All individuals in a variety are genetically very similar. Flowering is triggered by daylength. Varieties are each adapted to different latitudinal daylength zones. One field was all matured and yellow, except for 4 - 5 green plants which were off-type varieties, not triggered to flower in that zone. Was not popular in Manitoba until recently, when varieties were developed that were adapted to that area.

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Atriplex patula

Family Chenopodiaceae. Leaves are arranged oppositely, with variable shape. Can be difficult to identify. Appears similar to common lamb's quarters, but has a more branching growth habit, and a more pointed leaf.

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Ecballium elaterium

Family Cucurbitaceae. Seeds are sprayed out of the fruit with juice as it dehisces from the plant.

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Hypericum perforatum

Family Hypericeae. A perennial. An invasive species, introduced from Europe as an ornamental. Invades pastures and rangeland in the USA. Has a shrubby growth habit, with a stiff, woody stem. Leaves arranged oppositely (two per node). Leaves have tiny "perforations" where cells are translucent, appearing like holes; this is the reason for the species name. Flowers have many stamens. Contains toxic chemicals which can cause the skin to become photosensitive. Cattle and horses which eat it have weight loss nearly to death, as well as open skin sores. For humans it has medicinal properties as an anti-cancer drug and an antidepressant. Some farmers in BC grow and sell it for its medicinal values.

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Fragaria x ananassa

Family Rosaceae. A creeping perennial. Has vegetative propagation with stolons. Stolons can be a hindrance to production, growing between rows, and may be cut off. In the first year, there are annual weeds, and in the second year you get perennials.

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Family Orobanchaceae. A parasitic plant. Causes enormous yield loss in corn, sorghum, millet, and other grass crops. Seeds can live in the seedbank for 10 years. Originated from Africa and Asia. Identified in 1955 in North Carolina, and in view of the enormous damage potential, a federally based eradication program was started in 1957. The program was deemed a success, despite having slow progress. In 1957, there were 450,000 infested acres. By 2007, there was a 99% reduction to less than 3,400 infested acres.

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Helianthus sp.

Family Asteraceae. The fruit is the kernel, which lacks a pappus.

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Ranunculus acris

Family Ranunculaceae. Invades pastures. Grows into one tall stem with branches at the top. Leaf is unifoliate, but deeply lobed. Can be toxic to horses and cattle. Can appear similar to creeping buttercup, but has less lateral branching. Petals overlap more so than in creeping buttercup, but this is an unreliable distinguisher.

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Acalypha rhomboidea

Copperleaf

Family Euphorbiaceae. Cotyledons are obicular. First leaves have indentations which are forward-pointing. Flowers form clusters in the axils. Grows on the edges of shaded, moist areas, such as forests. Has natural tolerance to Pursuit, and can be found in agricultural fields. Can appear similar to pigweed.

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Vicia cracca

Family Fabaceae.  A legume. A perennial with rhizomes. Flowers are purple and symmetrical, arranged all facing one direction on the inflorescence. Can climb on other plants for support, using its tendrils, however it is not a parasitic plant. Often found near fences, in no-till systems, and pastures. It was introduced as a forage crop, but was replaced by more productive, higher yielding plants. Afterwards, it persisted as a weed. Has good qualities as feed for livestock. It is naturally tolerant of RoundUp, however it can be controlled by some other herbicides. Can be a problem in no-till soybeans.

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Cissampelos pariera

Family Menispermaceae. A pioneer species. Can grow to be very tall, and may be a problem in corn. A highly competitive species. Seeds can survive for 40 years in the seedbank.

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Amaranthus tuberculatus

Family Amaranthaceae. A successful weed species with cross-pollination. It is not tall enough to compete with corn. An invasive species. Found in USA, and starting to be seen in Ontario. One grower in Quebec found seeds stuck in a used combine brought from USA.

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Triticum sp.

Family Poaceae. Can be planted in the fall (winter wheat) or spring (spring wheat). If the weather is wet before harvest, the seeds can germinate on the head. Its WUE is 557.

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Trifolium repens

Family Fabaceae. A perennial.

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Silene latifolia

Family Caryophyllaceae. A perennial. Found in pastures and no-till systems. Leaves are opposite with a short petiole. The flower has a hairy bladder-like structure at the base, with protruding white petals.

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Fallopia convolvulus

Family Polygonaceae. An annual. It is quite common worldwide. The fourth most common weed in Western Canada. Appears when cereals begin to mature. The first leaves are heart shaped, pointed with two rear lobes. Can appear similar to field bindweed, but it has ochrea.

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Daucus carota

Family Apiaceae. The same species as carrot. Can harbour many of the same pests.

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Marah sp. 

Family Cucurbitaceae. Fruits have forced dehiscence.

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Allium ursinum

Family Amaryllidaceae. Has vegetative propagation with bulbs. A creeping perennial. Produces small bulbils in the inflorescence.

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Sinapis arvensis

Family Brassicaceae. Closely related to canola and mustard. Cotyledons are kidney-shaped, like in canola seedlings. Leaves at the base are long and rounded, but near the tip they are more triangular.

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Avena sp.

Family Poaceae. The most common weed in Western Canada. Has a large seed, and can emerge when planted as deep as 17.5 cm. Seeds have bristles and awns which react to moisture change by twisting around; this allows the seeds to roll, twist, and drill into the soil. The seeds spin if the awn gets wet. Cells on one side of the awn react to moisture differently than cells on the other side, producing the twisting motion. A single plant growing in the absence of competition can develop 86 km of roots in less than 3 months.

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Pastinaca sativa

Family Apiaceae. A weed that can cause skin irritation.

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Oxalis acetosella

Family Oxalidales. Fruits have forced dehiscence.

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Setaria pumila

Family Poaceae. Has silky hairs.

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Cyperus esculentus

Family Cyperaceae. An aggressive perennial. Releases toxic compounds from decaying dead material.

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