Spring flowering bulbs (hardy bulbs) such as snowdrops, crocus, daffodils, tulips and hyacinths need a cold period during the winter to jump-start
their growth cycle, so they will flower in the spring. They can be planted until the first frost. In general, spring-flowering bulbs will grow best in climate zones 3-8. They normally start blooming in
February, with snowdrops, and end in June, with alliums.