May. Just start with some of the early blooming species or botanicals. Then follow through with the various hybrid groups, ending with the Darwins. The minor bulbs offer an even longer bloom sequence. Start in February with winter aconite and snowdrops. End up in late May with English squill.
Most bulb suppliers give extra premiums for early orders.
Placing your order soon ensures that your bulbs will arrive when they ought to. So even though it's a long way off, think spring now and get your order in the mail. Planting time will be here before you know it, along with revitalizing cooler weather. Soil preparation is very important in getting bulbs off to a good start. Lime should be applied on the basis of a soil test in order to be assured of the proper amount.