Mow grape hyacinths along with your lawn. If they are in an area where you can't mow them, cut them to the ground with pruning shears. Every time the grape hyacinths begin to grow again, mow or prune them. Eventually, they use up their energy reserves and die.
Dig grape hyacinths up. Bulbs are typically planted about 3 to 4 inches beneath the soil. Remove all the bulbs and toss them out or give them away for others to enjoy.
Apply a herbicide that contains 2,4-D to the grape hyacinth's foliage. You must mix in a wetting agent or surfactant, available at garden centers, to the herbicide to improve the foliage's ability to soak in the herbicide. Follow the mixing and application instructions of any products used. If you live in a climate with lots of rain, this method may not work since the herbicide may be washed away before it is absorbed.