According to Martha Stewart, regular deadheading, or removing the spent daisy when it has died, initiates re-blooming and keeps the plant from seeding. A regularly pruned daisy plant will produce blooms until the end of the season. You need garden shears and a few minutes each day to deadhead your daisies and encourage repeated blooming.
Disinfect your shears
Wash your garden shears with an antibacterial cleaner to prevent the spread of bacteria and disease. Avoid damage to your shears; never disinfect them using use bleach or rubbing alcohol, as this corrodes your tool over time.
Cut the daisies
Deadhead daisies as soon as they start to wither. Make a horizontal cut at the closest lateral joint, the stem that protrudes from the main stalk and a leaf, just below the flower. If there is no lateral stem, cut at the next leaf grouping where there is no bud.
Maintain your flower bed
Take a few minutes each day to deadhead your daisies for consistent, regular blooms. Encourage re-growth when most of the buds are spent by cutting all stems evenly, 3 to 4 inches above the thick foliage at the base of each plant. If the plant doesn't bloom after this, it will foliate and set bud for the next season.