Pest Information
Common Name: Dandelion
Family Name: Sunflower
Latin Name: Taraxacum officinale
Provincial Designation: Common
Life Cycle: Perennial
Mode of Spread: Seed

Detailed Information
Provincial Situation: Dandelion is present throughout Alberta, but it is more frequent and abundant in Peace River Lowlands and Boreal Transition regions of Alberta. According to Alberta Weed Survey (2003) the ranking of this species in the various agricultural ecoregions is as follows:(BR>
Agricultural EcoregionFrequency1 (%)Density2 (%)Ranking
Mixed Grassland4.31.917
Moist Mixed Grassland10.41.110
Fescue Grassland21.20.910
Aspen Parkland17.11.316
Boreal Transition29.1211
Peace Lowland453.48
Alberta (All regions)16.71.711

1 Frequency: Percent of fields in which dandelion occurred
2Density = Average number of dandelions in occurrence fields.
Description: Dandelion is an almost stem-less lactiferous perennial herb. The leaves are clustered in a basal rosette; the leaf margins of dandelion are deeply lobed and toothed, generally 5 – 40 cm long and 0.7 – 1.5 cm wide. The leaf surface may be smooth or sparsely hairy. Dandelion inflorescence is bright yellow, up to 2 – 5 cm in diameter, and is produced at the top of hollow leafless stalks. The seeds are brown with a long tip and pappus and are disseminated by wind
Growth and Development (Life Cycle): Emergence: Dandelion flowers appear throughout the growing season, but they are most abundant in the spring.
Seed Production Dandelion is a prolific seed producer; each plant can produce 54 to 172 seeds per head, and a single plant can produce 2,170 to 23,000 seeds.
Seed germination: Dandelion seeds germinate at or near the soil surface under cool moist conditions when the soil temperature is at least 10 °C, usually from mid June to mid July. The seeds germinate best under a protective crop canopy.
Dormancy: Seeds have no seed dormancy when produced Longevity in the soil: Seeds may remain viable up to 9 years.
Dispersal: wind
How it Spreads (Mode of Spread): Mainly by seeds
Reproduction (Dispersal): Seeds: Reproducing mainly by seeds.
Roots: Dandelion has a deep, penetrating taproot that may be widely branched. Buds grow from the uppermost area of the root, producing a crown, which can divide to form numerous branches capable of regenerating, developing new shoots
Economic Importance (Beneficial Aspects): Detrimental: Dandelion competes with crops for moisture and nutrients and can reduce the yield potential of cereal, oilseed, forages and pulse crops.
Beneficial: Dandelion leaves can be used as a vegetable in salads. Its heads have long been used for making wine. It is commonly eaten by livestock and wildlife. This species is important source of nectar and pollen for bees
Origin: Europe
How to Control:
Cultural Options
Monitoring of fields and field margins Dandelions produce large quantities of seed, and the seed is spread by wind. Therefore, monitoring non-infested fields for dandelions and controlling dandelions before they set seeds in the field margins and fencerows is important.
Crop competition: Dandelion germination may be suppressed with good crop competition. It is important to use certified seed and competitive crop cultivars for planting.Crop rotation – Fertilize and re-seed weak forage stands. If this is not successful, work the forage crop down and re-seed to annual crop. Healthy perennial forages in the rotation for three to five years will reduce dandelion seed bank. Most annual crop competes well with dandelion as long as the crop stand is healthy and dense.
Tillage: Deep tillage to 10 cm will sever established dandelion taproots and destroy seedlings. However, tillage is not compatible with reduced tillage practices as it contributes to soil erosion.
Chemical Control: Dandelion seedlings and rosettes are most susceptible to systemic herbicides like glyphosate, glyphosate + Express TNG (tank-mixture), PrePass, 2,4-D and MCPA. There are five situations where dandelions can be controlled and/or suppressed with a herbicide application in conventional and a direct seeding system, pre-seeding (weed burn-down); early spring in-crop; pre-harvest; post-harvest, and termination of perennial forage.
Pre-seeding (Weed Burndown) Application:Glyphosate applied prior to seeding is registered for dandelion control in all crops. An application at 0.9 kg a.i/ha is registered for dandelion rosettes that are less than 15 cm (6 inches) in diameter; rates of up to 1.8 kg a.i./ha are recommended if dandelions are greater than 15 cm in diameter. The best results occur from applications earlier in spring because younger dandelions develop rapidly; later they become more difficult to control.The other herbicides registered for dandelion control prior to seeding of barley, oat and wheat are a mixture of glyphosate + Express TNG and the pre-packaged mixture of PrePass. A preseeding application of Amitrol 240 is also registered in wheat, barley and canola. However, in University of Saskatchewan study, Amitrol provided suppression of dandelion through June only (Sapsford et al 2005).
Early Spring In-crop Application: Dandelion spring rosettes can be controlled in-crop with several herbicides. However, dandelion seedlings germinate after the in-crop application window and, therefore, should be controlled in fall (prior to harvest or after harvest).
Pre-harvest Application:Pre-harvest applications of glyphosate applied at 0.9 kg a.i./ha are registered in western Canada for dandelion control in barley, canola (including rapeseed), dry beans, flax (including Solin), lentils, oats, peas, soybeans and wheat.
Post-harvest Application: According to University of Manitoba studies, fall (after crop harvest) is the best time to control dandelions. There are two reasons for this: 1) there is an increased translocation of herbicides into the roots along with net assimilates as plants get ready to over-winter; 2) most of the dandelions (seedlings that have emerged after in-crop herbicide application and plants that have emerged from root-stocks of the surviving rosettes have reached their peak emergence (Van Ackers et al 2005).
Dandelion Control in Perennial Forage:There are no herbicides available for control of dandelions in alfalfa. In grass pasture and hay fields, dandelions can be suppressed or controlled by 2,4-D, dicamba, dicamba + 2,4-D (tank mixture), Escort, Grazon, MCPA and Remedy. If there is a rotation out of hay/forages, glyphosate applied at 1.35 – 1.8 kg a.i./ha, 3 – 7 days prior to the last cut can be used for dandelion control/suppression. Another herbicide, Amitrol 240, is registered at rates of 1.7 to 6.6 L/acre for alfalfa and clover renovation and dandelion control.

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Last Modified: January 19, 2009

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