Permanently controlling dandelions (Taraxacum officinale) in a lawn is a long-term project, but combining several control methods is usually effective. Dandelions grow deep taproots that survive from one year to the next, resprouting after winter or after the dandelions' top growth is removed. Controlling dandelions involves removing or exhausting their taproots or else using herbicides that affect the roots and prevent dandelion seeds from sprouting. Dandelions are hardy in U.S. Department of Agriculture plant hardiness zones 3 through 9 and have invasive tendencies.
Weeding tools for controlling dandelions are often called dandelion weeders, and these help provide permanent control in a lawn. Most regular weeding tools aren't effective at removing dandelions because they break dandelion roots. Any part of dandelion root left in the soil can grow into a new plant. Dandelion weeders are long steel rods with two prongs at the end and a handle. They can often dig up dandelion taproots whole. Some weeders have a curved steel area attached to the rods.
A day or two after heavy rain or lawn irrigation, when the soil is moist, lift up the dandelion leaves to expose the plant bases, and push a dandelion weeder vertically into the soil where the leaves sprout from the ground. Insert the dandelion weeder until the base of the handle touches the ground. Slowly push the handle down, away from the plant, levering the dandelion roots out of the soil. You may need to work the handle backward and forward in the soil to loosen the roots.
Removing dandelions from a lawn once rarely gives permanent control, but repeated removal and mowing controls these weeds over the long term. Small dandelions sometimes appear from root pieces left in the ground, and new plants sprout from seeds.
Check the lawn every two or three weeks for new dandelion plants. Remove the plants with a dandelion weeder. Mow the lawn regularly to prevent dandelion flowers from forming seedheads. Overseeding bare patches of lawn where large dandelion plants grew discourages new dandelions and other weeds.
Herbicides for Established Dandelions
Systemic herbicides for broad-leaved weeds control dandelions in a lawn without harming grass. Dicamba, 2,4-D and MCPP are three herbicides that help control dandelions.
Put on long pants, a long-sleeved shirt, gloves and safety goggles before applying a herbicide. Spray the dandelions on a dry, still day when daytime temperatures are between 45 and 90 degrees Fahrenheit, and the dandelions are actively growing. If the lawn is dry, water it thoroughly and apply the herbicide three days later. Apply a ready-to-use product containing 0.05 percent dicamba, 0.12 percent 2, 4-D and 0.22 percent MCPP. Spray the herbicide on dandelion leaves and stems. Manufacturers' instructions vary from product to product, so read the label and follow the directions.
Herbicides for Dandelion Seeds
Dandelion seeds remain in a lawn, ready to sprout when the conditions are right, but pre-emergent herbicides prevent the seeds from sprouting. Dandelion seedlings appear when the soil is moist and temperatures are above 50 degrees Fahrenheit. Most seedlings grow when temperatures are around 77 degrees Fahrenheit.
A pre-emergent herbicide containing isoxaben controls dandelion seeds. Put on protective clothing, and apply a ready-to-use product containing 0.38 percent isoxben in late summer, early fall or early spring, before dandelion seeds sprout. Apply the product at a rate of 4.6 to 5.7 pounds per 1,000 square feet. Irrigate the lawn with 1/2 inch water to activate the herbicide.