In the early spring, flower heads remain open from sunrise to dusk, but in June to August, they close by noon. Unusual weather conditions, such as a sudden drop in temperature or very cloudy conditions, cause flower heads to remain closed. Flower heads open for 2 to 3 days in early spring and mid to late fall and for less than 2 days in the summer. Dandelion seeds are readily disseminated by the wind. Wind velocities of only 4 mph or more will keep seed air borne.
Dandelion seeds are non-dormant when produced.
Fall-applied glyphosate can also give acceptable control. Do not make glyphosate applications when the air temperature is below 50 F or if the plant has ceased active growth. Dandelion control in the spring with glyphosate applied alone is often only fair and is seldom acceptable. Postemergence applications of growth regulator herbicides usually provide acceptable dandelion control in corn. Deep tillage such as moldboard or chisel plowing will weaken the plant by disturbing the taproot and may make chemical applications more effective.