Even before winter begins, it is time to plan for it to end. Bulbs (including corms, tubers, rhizomes and tuberous roots) of many of the earliest spring flowers that bloom while the weather is still cool late in winter should begin to get planted about now. They are still dormant and not all that impressive yet, but have already stored everything they need to be ready to bloom as soon as they think it is time. Since the weather will be getting cooler through autumn before it gets warmer at the end of winter, even the earliest blooming of spring bulbs will stay dormant for a while, and have quite a bit of time to slowly disperse roots before their foliage eventually peeks through the soil.
Bulbs planted later will likely bloom later, which is actually an advantage for ‘phasing’ bulbs. Like vegetables, bulbs can be planted in phases every two or three weeks, depending on the duration of the bloom cycle of the particular bulbs involved. As one group finishes blooming, the next group starts blooming. Bulbs become available when it is time for them to be planted, and generally remain available long enough for a few phases to get added later when convenient, although there is always the threat of particular varieties getting sold out later in the season.
Phasing is only effective in the first season, since bulbs get established after their first bloom cycle, and will subsequently be on the same schedule as all their friends of the same variety. Bearded iris, calla, anemone and rananculus are not conducive to phasing, but instead bloom at a particular time, regardless of when they were planted.
Narcissus, daffodil, grape hyacinth, bearded iris and classic white callas are the most reliable of spring bulbs, and the most likely to naturalize, although bearded iris and callas will probably bloom quite late in their first year. Crocus, freesia and harlequin flower are almost as easy to grow. Anemone, rananculus, hyacinth, lily, tulip and the small colorful callas are tempting, but are not as reliable after their first year because the seasons are so mild here.