How to Kill Flower Bulbs

For many gardeners, flowering bulbs are one of spring's most eagerly anticipated sights. Their colorful early blooms herald winter's end. But even the loveliest flowering bulbs become unwelcome when they spread beyond boundaries or tastes change. Ridding your lawn and garden of unwanted flower bulbs may take time -- depending on the bulb, its surroundings and your desired results. Go the natural route with hands-on approaches, or speed the process with a chemical's help.

Manually removing offenders and their offspring is the most direct way to rid your garden or lawn of unwanted blooming bulbs. Bulbs are generally planted at depths of two to three times the size of the bulb itself. Their relatively shallow roots often sit less than 6 inches deep. Many bulbs pull out easily by hand from moist, crumbly soil, but their offsets may hide below. A long, thin spade or a close-tined broadfork lifts soil and bulbs in a process similar to harvesting root vegetables. By digging bulbs, you assure both the bulb and its offspring are gone. Digging bulbs best suits confined, garden plantings and may be impractical for bulbs in lawns.

Most bulbs depend on full sun and excellent drainage to return year after year. Too much shade weakens them and overwatering leads to premature bulb death. Create inhospitable conditions for undesired bulbs by turning proper culture upside down. Overwatering hits spring-flowering bulbs hardest while they put on their last push of autumn roots and when they enter post-flowering dormancy come summer. Too much water quickly leads to rot. Similarly, healthy bulbs need regular watering during their active periods of growth and blooms. Withholding needed water during these times weakens the bulbs. Following through with overwatering helps finish the job.

After bulbs bloom, they start storing fuel for next year's blossoms. Letting foliage wither and yellow naturally is critical to bulb longevity. Foliage captures essential energy; breaking the cycle prevents renewal. Cut all stems to the ground immediately after flowering -- when a bulb has exhausted its energy stores -- and you cut off its avenue for replenishment. Without a means to refuel, the bulb dies or struggles the following year. Keep all types of fertilizers, including turf applications, away from bulbs you want to kill. In lawns, mow foliage closely and keep it short for the same effect. Though it takes time, this method eventually kills naturalized bulbs without damaging the surrounding lawn.

Many home remedies and selective herbicides only kill plant parts above ground. They work like cutting or mowing foliage, but with chemicals instead of blades. Killing whole bulbs requires a systemic chemical that travels through plants to their roots. A ready-to-use, glyphosate-based herbicide will kill bulbs -- along with other plants, including grass. Use glyphosate when bulbs are actively growing; dormant plants don't transport chemicals to roots. Work on a calm, rain-free day, and spray foliage until thoroughly wet. Use a cardboard backdrop to shield any nearby plants. Wear protective clothing, including gloves and safety goggles, and avoid all contact with exposed skin. Tenacious bulbs may require repeat applications.