Tulip bulbs multiply on their own if the plants are maintained correctly during the growing season. Some gardeners choose to dig up their bulbs each year, but this method leaves multiplied bulbs in the ground for new growth next season, a process known as perennializing. It takes only a couple of minutes and a pair of pruning shears to facilitate the growth of new tulip bulbs.
Cut off blooms
If you leave the tulips outside while blooming rather than cutting them for a vase, use pruning shears to trim off faded flowers. This keeps the plant from dying before the bulb multiplies, according to Tulip.com. Don't cut back the leaves because they continue to transfer energy to the new bulbs.
Continue to water
Even though the blooms are gone, the plants need regular watering to promote more bulbs. Water enough to keep the leaves green throughout the season, and then let the leaves die naturally as the weather changes. Cut off the leaves once they are brown.
Add a 10-10-10 fertilizer to the tulips in the fall and again in the spring, once new growth appears. Apply the fertilizer to the top of the soil only to prevent burning the roots, and water thoroughly after application.