October is the ideal time to plant tulips, daffodils, and other spring-flowering bulbs in Iowa. When planted in October, spring-flowering bulbs have sufficient time to develop a good root system before the ground freezes in winter. If weather permits, bulbs can be planted as late as late November/early December.
Tulips, daffodils, hyacinths, and crocuses perform best in areas that receive at least 6 hours of direct sun per day. Snowdrops, snowflakes, and Siberian squill can be successfully grown in partial shade (2 to 4 hours of direct sun) to full sun. Bulbs also need a well-drained, fertile soil. Poorly-drained soils can often be improved by incorporating organic matter, such as compost or peat.
Plant spring-flowering bulbs in clusters or groups to achieve the greatest visual impact in the garden. When planting tulips and daffodils, plant 10 or more bulbs of the same variety in an area. Smaller growing plants, such as grape hyacinths and crocuses, should be planted in clusters of 25 or more bulbs. Plant bulbs at a depth equal to 3 to 4 times their maximum bulb diameter. Accordingly, tulips and daffodils should be planted 6 to 8 inches deep, crocuses and grape hyacinths only 3 to 4 inches deep. Large bulbs, such as tulips and daffodils, should be spaced 4 to 6 inches apart. A three-inch-spacing is adequate for crocuses, grape hyacinths, and other small bulbs.
After planting, water the bulbs periodically (if fall weather is dry) to promote good root development before the onset of winter.