The unique thing about bulbs is that they need little but water. Bulbs have a self-contained, highly developed food-storage mechanism that has adapted itself to life underground. Other plants can live in strange habitats like orchids in high trees or seaweed in the ocean but bulbs alone are able to provide nourishment for themselves in the most diverse kinds of soil. Even after lying dormant for months, enduring drought, frost or searing heat, bulbs can spring back to life continuing their species when conditions improve. Hence bulbs are easy and need little care.
From the moment the plants are actively growing, the soil should be kept moist, but never soggy. Bulbs do not need feeding before they flower. If your garden has poor soil the bulbs should be fed after blooming, when they are storing food for the following seasons growth. Feed the plants with a liquid or granular balanced fertiliser and continue to water in dry conditions until the leaves begin to die off naturally. This may take about two or three months.
After flowers have finished, cut off the spent flower stems but do not cut back the foliage. If you cut off the leaves before they died down naturally, the bulb will not have the reserves to grow and flower the following season.
When using fertilizers one of the best options is bone meal, especially for those bulbs left in the ground year round. Bone meal is a slow acting, long-lasting source of the phosphorus that bulbs need to build good root systems. Apply it at a rate of 5 to 6 pounds per 100 square feet, if you plant them in beds, and about a teaspoonful in each hole, if you are naturalizing the bulbs. Scratch the same amount into the soil around the bulbs every fall thereafter.
Another excellent fertilizer for bulbs is dry cow manure and of course compost. The best inorganic fertilizer is a general purpose one such as NPK 5-10-5, with 5% nitrogen, 10% phosphorus and 5% potassium. The higher percentage of phosphorus puts the emphasis on the development of the flower and the root system. Plants need nitrogen for healthy foliage, phosphorus for a strong flower and root system and potassium for firm stems and resistance to disease and cold. Other NPK ratios include 7-14-28 and 12-10-18 both putting more emphasis on firm growth.
Most summer flowering bulbs are not winter hardy. Therefore the bulbs should be lifted in colder climates. As a general rule we advice the following:
In climate zones 4 and 5
The bulbs should be lifted in the fall if you want to use them again next year.
In climate zone 6
Give the bulbs some protection from the frost by covering the soil with evergreens or mulch.
In climate zones 7 and higher
No protection needed.