In Pennsylvania, the best time to plant flowers largely depends on the type of flowers and the local planting zone, but generally:

• Spring planting is ideal for most annuals and perennials once the last frost has passed, which typically occurs between mid-April and early May depending on the region. For example, zones 5, 6, and 7 have varied last frost dates, such as May 4-5 in Harrisburg to around May 29 in Meadville. Planting after these dates reduces frost risk for young plants. Cool-season flowers like pansies can tolerate some frost and can be planted in late April or early May, while frost-sensitive plants should be planted in mid-to-late May.

• Fall planting is also beneficial, especially for bulbs like tulips (planted 6-8 weeks before hard frost) and perennials like peonies (best planted late September to early October). Fall planting allows plants to establish roots before winter and bloom in spring or summer.

• For wildflower gardens, spring (to early summer) and fall are the best times to plant.

• Early garden preparation and soil enrichment can start as early as late February to early March when the ground becomes workable.

In summary, for most flowers in Pennsylvania, plant annuals and perennials in spring after the last frost, and for bulbs and some perennials, fall planting before the ground freezes is preferred. Keep local frost dates in mind to time your planting well.