Answer: To be honest, many of the showiest tulips just don't last very long, and bad drainage can make them disappear even faster. The best you can do to encourage them is to plant them in a spot in rich soil with full sun and good drainage, prepare the soil about a foot deep, remove spent flowers to conserve the plant's energy, allow the foliage to grow on and then wither naturally (this looks awful but replenishes the bulbs) and possibly feed the foliage two or three times with a liquid fertilizer to try to maximize their performance. Finally, you might try some of the smaller and earlier rock garden type tulips; the Greiggii hybrid tulips tend to perennialize more successfully than most other types.
If there is no foliage coming up from your earlier planting, then I suspect it has, as they say, faded away.
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