Larger sized, more mature plants will usually cost more. Annuals are not affected by winter hardiness. The last frost in spring affects planting dates and the first frost in fall ends the season for most annuals. The following maps provide a guide to these dates. Many perennials can be grown from seed, but they are more often purchased as transplants.
Annuals are even easier to grow from seed, but most gardeners choose to purchase transplants.
Bulbs are usually sold in a dormant state. Mail-order nurseries ship dormant plants, growing plants, and bulbs at the correct planting time in your area. They also can be potted up and grown in a cold frame. Plant bare-root and potted plants in a hole large enough to allow spreading out of the root system. Plant at the same depth as they originally grew.