Choosing the right bulbs involves more than just selecting colors and cultivars. Timing, bulb size, and most importantly, bulb health are equally significant factors in designing your garden.

Before purchasing any bulbs, know the differences in bulb types. Along with true bulbs, several types of flowers, sold as bulbs, grow from the underground stem growth of rhizomes, tubers, and corms.

Bulb health
Healthy bulbs are firm, well rounded, and heavy for their size. Although bulbs come in a range of colors, some even with distinctive patterns, color should be uniform with no dark patches or light splotches. Discard any bulbs with weak spots or spongy area, which are signs of rot caused by disease or other damage.

Bulb Size
First, it helps you select cultivars and decide where to place them in your spring flower garden. For instance, crocus and anemone bulbs are tiny imps that beg a front row or outside border seat, while giant tulip or daffodil bulbs stand tall in back rows or keep watch over the center of your garden.
Second, larger bulbs, within a particular cultivar, are generally more robust than smaller bulbs and produce stronger, healthier plants and blooms.

Timing
When choosing bulbs for a spring flower garden, consider both when they need to be planted as well as when you want them to appear.
Most spring bulbs need to be planted in late summer or autumn. Spring bulbs usually need to be planted when it is cool enough to keep them from sprouting, but warm enough to allow roots to become established before winter.
All spring bulbs need a cool weather rest period below 50F in order to sprout successfully.