Background

Although dandelions are for the most part considered a weed, they have many interesting, unique and valuable characteristics. Dandelions are grown commercially for several uses, including leaf legumes, insect repellent, coffee replacement (roasted/ground roots), and various medicinal purposes. The leaves are very high in vitamin A and C, and contain more iron than spinach. There are usually 50 to 150 seeds produced per head, however, a single plant can produce up to 10 heads. Spread by wind, the seeds germinate on the soil surface once the temperature approaches 100 C. This weed can also reproduce vegetatively from pieces of tap-root. Tap-roots of mature plants that are injured by tillage will form callus tissue that can generate new plants. Mature dandelions are only suppressed by sweep tillage or disking, low glyphosate rates and many of the common in-crop herbicides.

Control

In direct seeding systems, dandelion control relies on good crop competition and the timely application of systemic herbicides. Various options are available for control of dandelion seedlings, while mature dandelions are much harder to control.

Pre-seeding Application

Glyphosate rates of 1.0 L/acre prior to seeding will provide relatively good control of seedlings, but the larger plants (5” or more) will only be suppressed. Increasing the rate of glyphosate up to 2.0 L/ac will help increase the consistency of dandelion control, but will still only suppress very large plants.

Early Spring In-crop Application

In-crop control of dandelion relies on good crop competition. Several herbicides are registered in cereals for in-crop suppression of dandelion; however, these herbicides don’t provide long term control and generally show significant re-growth in the fall.  The strongest active ingredient on dandelions in crop is Chlopyralid, which is better known as Lontrel.  Products that have Lontrel in them such as Spectrum and Prestige are excellent choices for annual dandelion control and strong suppression of winter perennials.

Pre and Post-harvest Applications

Fall tends to be the best time to control dandelions, providing the weed is actively growing. Although dandelions by and large have the ability to continue to grow late into the fall, leaf disease and other environmental conditions can sometimes restrict the amount of chemical uptake by the leaves. At this time, it’s important to make sure the center of the plant (growing point) has green growth (actively growing). Provided the above conditions are addressed, 1.0L/ac of glyphosate will give good control, and help reduce the overall dandelion population. In the fall, the dandelion will be storing energy down into the roots for the winter, therefore the uptake is much higher on perennial weeds in the fall then it is in the spring.  This stronger uptake has proven to show a greater control level on perennial weeds such as dandelion and thistle in the fall.

SVF’s Work

During the fall of 2006, SVF, with the support of DowAgro Sciences, applied glyphosate alone and in combination with florasulam (Prepass) to a field with numerous dandelions, both established and seedlings. The results were positive and Prepass has since been proven as one of the strongest tools to control Dandelions.  Applying in the fall is your best timing, however applying Prepass in the spring can also have excellent results.

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