Knock Out roses have been bred for easy care when planted in the ground soil or in containers. Container grown roses are cared for in much the same way as those grown in the ground, save treatment during winter in climes where frost or freezing temperatures are common. Knock Out roses benefit from consistent, very basic maintenance and will perform with a long bloom season from spring through fall each year.
Water your Knock Out roses to keep the container soil evenly moist but not sopping wet at all times during the growing season. Never let more than the top 1/2 inch of soil become dry to the touch. Water deeply and thoroughly ensuring that the drainage holes remain clear and any excess water is allowed to drain away readily.
Fertilize your roses in the spring, after the last frost has passed, with a balanced rose food formulation with a guaranteed analysis of 6-6-4 or a similar ratio. Use an organic or synthetic product as desired, but always apply according to the product label dosing directions, over wet soil. Cease fertilizer applications by the late summer to prevent late season growth that may be killed by low winter temperatures.
Prune your roses as needed to control the size and shape of the plant or to re-invigorate growth, if desired. Spring pruning is best and the plant can be pared down to just a foot or 18 inches above the crown each year, as needed. Place all cuts on the bias just above a leaf node or bud. Collect and clear away all cuttings to prevent breeding disease on the soil surface.
Move your rose planted containers indoors to a dim and cool location after the second frost of the fall or winter has occurred. Situate them in a spot where they will not be buffeted by cold winds or drafts from doors or windows.
Keep the soil lightly moist throughout the winter storage period--not wet, but not completely dry either.
Move the pots back outside into a sunny location in the spring when the last threat of frost has passed, where they will have benefit of at least six hours of sun daily.
Resume a regular watering regimen for the roses in the spring, keeping the soil evenly moist throughout the pot at all times.