One important growing condition is that crocuses must have a well-drained soil. Crocus bulbs remaining in the ground will always bloom a bit earlier than the ones planted the previous year. The calyx-shaped flowers open only when the sun shines or when there is a lot of light they close up in rainy weather and at night. Crocuses are lovely in lawns as well as in the perennial border where they join the other very early perennials in ringing in the flowering season. Crocuses have narrow leaves with a silver-grey stripe down the middle.