Dandelion

Overview

Dandelion (Taraxacum offinianale), is a broadleaf perennial weed that can be found in lawns, nursery crops, and landscapes throughout the United States. It has the ability to survive many different soil types, environmental conditions, and management practices; thus, it is a commonly found weed in lawns throughout the northern half of the U.S.

Identification

Dandelion, a well-known perennial broadleaf weed, thrives in full sun and moist soils, yet is adaptable to various environmental conditions. It emerges in early spring from overwintering leaves and a taproot. The leaves are distinctive, with wavy margins and ‘teeth’ pointing downward towards the base of the rosette.

The dandelion’s strong taproot allows it to regenerate even if parts of it survive, making it difficult to eliminate, especially in Indiana lawns. Hoeing may not effectively kill the plant due to its resilient taproot, which also challenges complete control, even with herbicides.

In Indiana, dandelions typically bloom from late April to mid-May. They produce yellow, sunflower-like petals on long, leafless, erect stalks. These flowers usually appear in the plant’s second year. After flowering, the dandelions form a globe-like, white seedhead with feathery ends, aiding wind dispersal. Each seedhead can produce 140 to 190 viable seeds, contributing to the widespread dandelion populations in Midwestern U.S. lawns. Dandelion seeds germinate from late spring to early autumn, following flowering and seed dispersal.

Cultural control

“To control dandelions, no specific method is exclusively effective. However, removing as much of the taproot as possible can significantly improve control. Tools like dandelion knives are designed for extracting individual plants with minimal soil disturbance. These tools work best when they successfully remove the entire taproot. Altering fertilization methods to reduce potassium (K) or potash (K2O) levels might also help decrease dandelion populations, but this approach is slow and may take several years to show results. On the other hand, implementing management practices such as increasing mowing heights, enhancing soil fertility, and regular irrigation can encourage the growth of dense, healthy turf. This robust turf is more likely to outcompete dandelion plants as they germinate.”

Biological control

The fungus Sclerotinia minor can selectively remove dandelions from cool-season lawns. In Canada it is formulated and sold as Sarritor, a new biological weed control product. This product has yet to be released in the US as of 2015.

Chemical control

Herbicides containing 2,4-D are highly effective in controlling dandelions. The optimal time for controlling perennial broadleaf weeds like dandelions is in the fall. During this season, both amine and ester formulations of 2,4-D are most effective. For spring infestations, particularly in cooler months like April, ester formulations of broadleaf herbicides or products like florasulam (Defendor) enhance dandelion control. However, applying ester formulations too early in spring may reduce their effectiveness. As spring progresses and temperatures rise, it’s advisable for turf managers to switch to amine formulations. This is because amine formulations not only become more effective in warmer temperatures but are also safer to use near landscape plantings, gardens, and other sensitive areas compared to ester formulations. For detailed guidance on choosing between amine and ester formulations for postemergence broadleaf weed control, refer to the article ‘Should I use an amine or ester formulation for postemergence broadleaf weed control?