Plant hyacinth bulbs in an area with well-drained soil that receives six or more hours of daily sunlight during the spring blooming season. Plant the bulbs with the flat bottom of the bulb 6 inches beneath the soil surface, and space the bulbs 2 inches apart in all directions.
Water hyacinths when they begin to emerge in spring. Provide about 1 inch of water weekly unless there is an equal amount of rainfall. One inch of water is enough to moisten the top 6 inches of soil. Water hyacinths only when they are actively growing.
Dissolve 5 tablespoons of soluble 10-10-10 fertilizer in 1 gallon of water. Water every 10 square feet of hyacinth bed with this solution when the plants resume spring growth. Annual fertilization helps the bulbs replenish their nutrient stores so that they can bloom again the following year.
Cut off the flower spikes after the blooms begin to wilt, but leave the foliage in place so that it can continue to collect nutrients and energy for the bulb. Cut back the foliage to the ground after it yellows and dies back, about six weeks after the flowers die.
Dig up the hyacinth bulbs every three years, and divide them so that the bed doesn't become crowded, which reduces bloom. Break apart the bulbs, and replant them at the proper depth and spacing. Work 5 tablespoons of 10-10-10 fertilizer and 2 cups of bonemeal into the top 6 inches of every 10 square feet of soil before replanting to replenish the nutrients in the site.
Spread a 2-inch layer of mulch over the bed after the first frost. Mulch insulates the soil, which protects the bulbs from winter temperature fluctuations that could otherwise result in frost heave.