All five of these methods can be combined to pinpoint the ideal planting time for each species of plant within an individual garden. Naturally, though, each type of plant has unique requirements that must be considered.
Bulbs
Spring-flowering bulbs such as tulips, daffodils, and hyacinths should be planted in the autumn, four to six weeks before the first frost. Because spring-flowering bulbs need a period of dormancy to germinate, in climates with no winter frost, bulbs will have to be chilled in the refrigerator from approximately November to March or forced in pots. For summer-flowering bulbs, the planting time is late spring, six to eight weeks after the last frost. According to the tradition of planting by the phases of the moon, bulbs should be planted when the moon is waning, between the full moon and last quarter.
Perennials
Perennial flowers and herbs should be planted either in early spring or early autumn. Almost all can be planted in spring when there is no longer any danger of frost. Some perennials such as phlox (Polemoniaceae ssp.), alyssum (Lobularia maritima), and most wildflowers, along with cool-season herbs like dill and cilantro, can be planted in autumn. To give these plants time to establish themselves, plant them four to six weeks before the first frost. Turf grasses and ornamental grasses are also perennials. Cool-season grasses such as Kentucky bluegrass, fescue, and rye grow best if sown two or three weeks after the last frost in spring, but before the summer heat arrives. These grasses can also be sown in autumn four to six weeks before the frost, but should be kept watered and protected with mulch or a similar covering. Warm-season grasses such as Bermuda, big bluestem, and and zoysia prefer air temperatures between 70 and 90 F (20-30 C).
Annuals
Garden centers usually display annuals before the plants are ready to go into the garden, so don't assume that because you can by them they’re ready to make it on their own outdoors. Annuals planted too early in the spring may end up stunted by the chilly weather and never fully recover. They may also fall victim to a late frost. On the other hand, annuals planted too late in the season won’t have time to mature enough to bloom well. Nearly all annuals, especially warm-climate natives like bleeding heart (Clerodendrum thomsoniae), Amish cockscomb (Celosia cristata), and coleus (Coleus blumei), should be planted when air temperatures are in the 70 and 80 F (20-25 C).