Dandelions, despite being much loved by children for their bright yellow blooms and puffy seed heads, are one of the great scourges of the home landscape. Practically ubiquitous, dandelions require constant vigilance to get them under control. Sooner or later, many homeowners look for a weed killer to help them take back control of their properties from these persistent broadleaf weeds.
Dandelion is a perennial, growing back each year from its thick, long taproot. Spreading on the wind by use of its familiar downy seeds, it colonizes almost any bare patch of soil it lands on, especially in sunny locations. Dandelions are active and produce flowers and seed heads throughout the growing season, and even grow year-round in areas with warm winters.
Prevent the germination of dandelion seeds by following good cultural practices for lawns. Turf that is thick and healthy, as well as lacking excessive thatch, is less susceptible to weed invasion. Keep ornamentals in garden beds healthy and full to shade the soil and prevent germination. Use mulch to shade seeds and keep the soil cool.
The preemergent broadleaf herbicide isoxaben is effective against dandelions. It must be applied in early spring, before dandelion seeds germinate. Always use herbicidal products according to label directions. Preemergent controls will not kill dandelions that have started to grow, or those returning from the year before.
Post -Emergent Control
Most post-emergent herbicides labeled for broadleaf weeds are effective in killing dandelion plants. Look for the active ingredients glyphosate, triclopyr or 2,4-D. These products will not prevent seeds from germinating. Use them as needed and only in affected areas.
Post-emergent broadleaf weed killers will also kill desirable ornamentals, so keep the spray from getting on shrubs, trees and flowers. Spot treating individual dandelions in lawns with a quick, controlled squirt helps keep the spray in control. When spraying in garden beds and near shrubs, use a sheet of folded cardboard to avoid over-spraying.
To keep dandelions from getting out of control, pull up individual plants, getting as much of the perennial taproot as you can. Picking dandelion flowers and seed heads before they set seed prevents the spread of seeds until you can apply an herbicide. Keep flower beds mulched to discourage seed germination. If seeds germinate in mulch, the loose structure allows easy pulling. Bag all parts of dandelions and put them in the garbage to avoid spreading them on the property.