Apple trees (Malus domestica species) are best planted at the end of their winter dormancy, weeks before the new leaves and flower buds break. However, container-grown plants can be planted any time of year as long as the soil is not frozen. The geographical and elevation differences across the state of Pennsylvania slightly change the ideal spring or autumn months for planting.
As long as the apple tree is dormant, not displaying foliage or flower, it can be planted in soil that is not frozen and is easily dug.
Apple trees raised in containers can be planted any time of year as long as the soil is not frozen and generally if drought conditions are not prevalent. Bare-root apple saplings must be planted in early spring; balled and burlapped (B&B) plants are best planted in early spring or early autumn outside of the heat or drought stresses of summer.
The western third of Pennsylvania, the areas with lower elevations to the west of the Appalachian ranges, resides in USDA Plant Hardiness Zones 5 or 6. Planting apple trees is ideal when the plants are in their winter dormancy just prior to spring, from mid-March through mid-April. As the winters are generally cold but mild, fall planting of containerized apples up until early October can also be done.
Central Pennsylvania (Intermountain)
The central parts of Pennsylvania have variable elevation and climate, but generally fall into USDA Plant Hardiness Zones 4, 5 or 6. Local microclimates exist and affect length of growing season as well as duration and severity of winter cold. As long as soil is unfrozen, spring planting of apple trees can occur from mid to late March to early May, ideally. In mild pockets of this hilly region, autumn planting in late September can also be done.
Southeastern Pennsylvania refers to the lower elevation from the eastern slopes of the Appalachian ranges to sea level near Philadelphia. This region encompasses USDA Plant Hardiness Zones 6 and 7. Spring planting is ideal for dormant apple trees, from early March to late April. Mild, prolonged autumns also find the month of October generally amenable to apple tree planting if needed.