Pruning is a routine but often misunderstood aspect of landscape maintenance. For homeowners in Wisconsin, the climate includes harsh winters and brief growing seasons, making timing a critical factor. Misjudging the correct period for cutting can result in a complete absence of flowers or significant damage to the plant’s health. Understanding the fundamental growth cycles of different shrub varieties ensures vibrant displays and robust plant structure.
Trimming Shrubs that Flower on Last Year’s Growth
Shrubs that bloom in spring on “old wood” are often pruned incorrectly. These plants, including Lilacs, Forsythia, and Mophead Hydrangeas, set flower buds during the previous growing season. The buds form on woody stems that matured last summer and must survive the Wisconsin winter to produce spring blooms.
Pruning these shrubs in late fall, winter, or early spring removes the developing flower buds, sacrificing the floral display. The mandatory timing is immediately after the flowers fade, typically late May through late June. This window allows the plant to complete its bloom cycle and provides time for new growth to set buds for the following spring.
Waiting too long into the summer disrupts the plant’s process of forming next year’s buds. For Lilacs, remove spent flowers and thin older, less productive stems right after the petals drop. This stimulates vigorous new growth that matures over the summer and carries the flower buds through the cold months.
Maintenance for Non-Flowering and Evergreen Bushes
Shrubs grown for foliage, structure, or that bloom on “new wood” have a more flexible pruning schedule. This category includes Boxwood, Yew, Arborvitae, and summer-blooming shrubs like Japanese Spirea and Smooth Hydrangeas. Since summer-flowering varieties produce buds on current season growth, they can be pruned harder early in the year.
For aesthetic shaping and size reduction of evergreens and non-flowering shrubs, the optimal period is early spring before new growth begins, or mid-summer after the first growth flush has hardened off. Shaping evergreens like Yews and Arborvitae is best done after new growth expands, typically late spring or early summer, allowing subsequent growth to conceal cuts.
Pines should have their new candle growth snapped or cut back in late May or early June to promote a denser, more compact habit. All major pruning must cease by mid-August for these varieties. Cutting past this point encourages tender, immature growth that will not harden before the first hard frost.
Late Winter Pruning for Structure and Damage Repair
Late winter, generally February and early March before buds break, is ideal for dormant pruning. The absence of leaves allows a clear view of the branching structure, making it easier to identify and remove problematic wood. Pruning during dormancy minimizes stress, as metabolic processes are slowed.
The focus is structural improvement and corrective care. This includes thinning dense areas to improve air circulation, removing crossing branches, and cutting out dead, diseased, or damaged wood. Cuts made now heal efficiently because diseases and pests are largely inactive, reducing infection risk.
Late winter is excellent for shaping deciduous shrubs that flower on new wood. This timing must be avoided for spring-blooming, old-wood shrubs unless size reduction is the goal at the expense of flowers. Evergreens tolerate less aggressive dormant pruning. Pruning now ensures shrubs are structurally sound and prepared for vigorous growth when spring arrives.