Since spring-flowering flower bulbs can easily withstand even a fairly harsh winter, almost all of them can be planted outside. They even need a cold period in order to flower. The exceptions are Hippeastrum (Amaryllis) varieties and Narcissus ‘Paperwhite’. These should not be planted outside, but should be planted in pots and kept in a cool spot until December or January. At that time, they should be placed in a warm room where they will produce flowers.