Chemical control of dandelion using a broadleaf herbicide is best achieved from September to early November or March to May in Zones 6 and 7. Note that spray dates in northern zones start later and end sooner; in Zones 8 or above, dates begin sooner and end later.

For effective use of herbicides, weeds need to be actively growing, not stressed by a prolonged dry spell. Do not spray when foliage is wet with dew, raindrops, fog, or irrigation. DO NOT spray when wind is strong enough to carry mist to your neighbors. Most herbicides have a temperature range in which they perform best; read labels carefully.

Contact your local Extension office for specific chemical recommendations and spray dates.