There are many factors that contribute to the failure of flower bulbs to perennialize in the garden.  First, The bulb may not be hardy in the climatic zone.  Second, the bulb size was reduced below the minimum required for flowering.  This size varies with the bulb species and cultivar.  Some of the factors affecting perennialization are as follows:

• Bulb species or cultivar was not adaptable to specific climatic zone or microclimate.
• There was poor drainage in the planting site.
• pH greatly exceeded the 6 to 7 range.
• Site had high salt content and roots were burned.
• Bulbs were not properly fertilized to maintain or increase bulb size.
• Site had improper light level for adequate photosynthesis to take place.
• Large, shallow rooted trees were in the same site and the tree roots were too competitive.
• Foliage was not allowed to senesce long enough for bulbs to increase in size.
• Foliage was bent over and/or tied and inadequate photosynthesis took place.
• Heavy freezing damage occurred.
• There were serious diseases.
• There was a prolonged drought that affected plant growth and development.