Bulbs provide a good investment for the money spent and they supply years of spring color in your yard. Fall is the prime time for planting hardy spring-flowering bulbs. Most bulbs can be planted until the ground is frozen.
Good soil drainage is essential for raising bulbs. If you have a soil with a high clay content, it can be improved by adding compost, peat moss or some other source of organic material. The organic material should be worked into the top 12 inches of soil. Both spring and summer bulbs need phosphorous to encourage root development. Mix bonemeal or superphosphate with the soil in the lower part of the planting bed as it is being prepared.
Before deciding where to plant bulbs in the landscape, consider the light requirements of the plant. Does the plant require full sunshine, partial shade or full shade? Since early spring bulbs bloom before most trees or shrubs leaf out, they can successfully be planted under trees and shrubs. Many summer blooming bulbs require full sun or partial shade.
The general rule of thumb for is to plant two to three times as deep as the bulb is tall. Planting depth is measured from the bottom of the bulb. This rule of thumb on planting depth does not apply to summer bulbs which have varied planting requirements.
Tulips, daffodils and hyacinths should be planted with the nose of the bulb upward and the root plate downward. The best method is to dig and loosen the entire bed to the proper depth. Press the bulbs into the soil in the planting area and cover with soil. This method is better than trying to plant bulbs one by one with a bulb planter.
Water the bulbs following planting. This will help settle the soil in the planting bed, plus provide moisture needed for the bulbs to start rooting. Fall-planted bulbs must root before cold weather. Avoid over-watering at planting time since this can result in bulb rot.
For both spring and summer bulbs, start watering when the flower buds first appear on the plant if the soil is dry. Shallow watering will not do the job. Remember that the bulbs may have been planted six to eight inches deep, so the water needs to soak to that depth. Through the bud, bloom and early foliage stage, add about one inch of water per week if this amount has not been supplied from rainfall. Water with a soaker hose to keep water off the bloom.
One of the visual problems with spring bulbs is the foliage that remains after bloom. The foliage can become unsightly if the bulbs are planted in a public area of the landscape. Foliage should not be mowed off until it turns yellow and dies back naturally. The foliage on the larger bulbs, like tulips and daffodils, will take several weeks to die back. There are several ways to divert attention from the yellowing bulb foliage. Interplant the bulbs in the spring using one or two colors of annuals. Place bulbs behind the plants on the front edge of a border planting. Plant taller flowering bulbs behind lower growing foreground shrubs. Or plant bulbs with groundcovers and perennials like hosta or daylilies.
Once the foliage dies back or matures in the late spring or early summer, the bulb is dormant. Summer is the dormant period for spring bulbs and this is the time to dig them if needed. If the choice is to dig bulbs, they should be stored in a well-ventilated place and replanted in the fall. Every five years daffodils and crocus should be dug and replanted to prevent overcrowding. The first sign of overcrowding will be a decrease in the flower size, uneven bloom and uneven plant height. When this occurs, dig, spread bulbs out and replant immediately.
Ron Cornwell is a University of Illinois extension educator. For more information go to www.urbanext.uiuc.edu.