When to Prune Knockout Roses in Pennsylvania: Winter vs. Spring Timing

The Risk of January Pruning

Pruning stimulates growth. In Philadelphia (zone 6b/7a), a January warm spell can trigger tender new shoots that a subsequent freeze will kill, causing dieback and potential disease entry.

Safer Approach

• Light shaping now only if canes are hazardous (e.g., blocking paths).
• Main pruning: late February to early March as buds swell.
• Mid-summer trim to control size if needed.

Fertilizer Warning

Knock Outs need minimal feeding—one main application in spring. High nitrogen (first number >5) creates monster bushes that require constant pruning.