Planting Bulbs: Select Well-Drained Location for Bulbs

The performance and durability of many bulbs is greatly influenced by both surface and internal drainage of the soil around them. Low spots that stay wet in winter and spring are especially damaging to tulips, hyacinths, daffodils and similar types of bulbs. If no other location or soil is available other than one that stays fairly wet, consider building a raised bed or large mound for bulb planting. Many gardeners feel that when there is slope to the land, drainage is adequate. This is not always true. In the case of heavy soils in which the air space remains well below 50 percent of total soil porosity, water is held tenaciously against gravity.

This condition reduces the amount of oxygen available to plant roots, and reduces growth and development. Less root growth from the bulb means less nutrient uptake and bulbs gradually decline. Tight, compacted soils are not ideal for bulbs in any location, they are particularly devastating whenever they become water-logged. Sandy soils, and other soils that are fairly loose internally, provide better growing conditions for bulbs even in marginal drainage situations.

Sandy soils, however, often have low fertility and may dry out quickly. The texture of heavy clay soils can be improved by the addition of organic matter such as well-rooted leaf mold, old manure or peat moss. Sand may also be added if available. When adding organic matter to help improve tight soils, use at least three to four bushels per 100 square feet of planting area. This, same amount will also be helpful in extremely sandy soils where water retention and nutrition needs improvement.

Most bulbs do not like soils that are quite acid. If the pH of the soils is below 6.5, ground limestone should be mixed into the soil at planting time. Add about five pounds of limestone per 100 square feet of area for each 0.5 pH value needed to bring it to near 6.5. For example if the pH must be changed from 5.5 to 6.5, 10 pounds of limestone per 100 square feet of planting area are needed.

Also, while preparing the soil for planting, a fertilizer may be added. One without nitrogen, or very low in nitrogen, may be used. Add about three to four pounds of such a fertilizer per 100 square feet of bed area. Any additional fertilization should then be delayed until new growth develops in spring. Most large bulbs are planted from four to six inches deep. In heavy clay soils bulbs should be planted about four inches deep (to base of the bulb) while in sandy soils the depth closer to six inches is adequate. In well drained soils, there is more flexibility in planting depth than in tight, poorly drained soils.

Because large bulbs are planted fairly deeply, thorough soil preparation is important. Soil should be well worked to organic matter and other materials are mixed at least six inches deep, the roots of bulbs grow well below the bulb itself. It is the condition of the soil in the root zone that provides the most influence on the performance of the bulb. At times, a few bulbs are desired where drainage may be marginal, and soil can not be worked for best improvement. Placing sand in the bottom of each planting hole directly beneath each bulb can reduce chances of damage from short-term water-logging. The is method has little value if long-term wet conditions develop.

Source:

http://www.thegardenhelper.com/springbulbs.html