Winterizing a rose bush prepares it to survive the cold, drying winds, and damaging freeze-thaw cycles of winter. The goal is to insulate the most vulnerable parts of the plant, ensuring the rose remains dormant and protected until spring. The specific actions required depend significantly on the severity of the local winter climate. Taking proactive steps in the fall ensures the plant hardens off properly for survival.
Preparing the Rose Bush for Dormancy
Preparation for winter dormancy must begin weeks before the first expected hard frost to signal the plant to slow its growth. Halt all fertilization approximately six to eight weeks before cold weather arrives. Continuing to feed the rose encourages soft, tender new growth, which is highly susceptible to frost damage and draws energy away from fortifying the roots.
Watering should be gradually reduced but not stopped entirely, as the plant needs to be well-hydrated before the ground freezes solid. A final, deep watering before the deep freeze provides moisture that helps insulate the roots and prevents desiccation of the canes. Garden sanitation is important; removing fallen leaves and debris from around the base prevents fungal spores and pests from overwintering.
Protecting the Graft Union
For most hybrid tea, floribunda, and grandiflora roses, protecting the graft union is the most important winterizing step. This swollen area, where the desirable rose variety is joined to a hardy rootstock, is the most vulnerable point to cold damage. If the graft union is damaged, the named rose may die back, leaving only the rootstock to grow.
The common method for protection is “hilling,” which involves mounding insulating material around the base of the plant. After the first few hard frosts prompt dormancy, but before the ground freezes solid, create a mound 10 to 12 inches high over the graft union. Suitable materials include clean, weed-free soil, well-rotted compost, or shredded leaves.
Source fresh material or use bagged compost rather than scraping soil from the rose’s roots, which can expose them. Avoid materials like fresh wood chips or heavy, wet soil, which retain too much moisture and promote rot. Before hilling, remove any remaining leaves on the lower canes to reduce the chance of fungal diseases developing under the mound.
Advanced Methods for Cold Climates
For gardeners in USDA hardiness zones 5 and colder, protection of the base alone is often insufficient. These regions require methods to protect the entire cane structure from severe freezing temperatures and harsh winter winds. The first step is to lightly prune the canes back to a manageable height, typically 2 to 3 feet, to prevent wind damage and make covering easier.
One effective technique involves placing a protective structure over the entire bush, such as a rose cone or a wire mesh cage. Rose cones must have ventilation holes to allow air circulation, preventing heat buildup that could break dormancy or promote fungal growth. For a cage structure, fill the wire cylinder with a loose, insulating material like straw, pine boughs, or shredded leaves, which trap air and provide a buffer against the cold.
Another approach for very tall or climbing roses is to gently detach the canes from their support, tie them together, lay them on the ground, and bury them under several inches of soil and mulch. This method, sometimes called the “Minnesota Tip,” shields the canes from desiccation and severe temperature swings, which commonly cause dieback in exposed winter conditions.
Spring Uncovering and Cleanup
The process of removing winter protection in the spring must be gradual to prevent shocking the plant with sudden exposure to sun and wind. Begin to remove the coverings as temperatures start to rise consistently, typically after the danger of a deep frost has passed. Rose cones or dense wrappings should be removed first on a cloudy day or in the late afternoon to allow the plant to acclimate and avoid sun scald.
The hilled material around the base should be removed in stages over a period of one to two weeks, rather than all at once. This slow process allows the plant to adjust to cooler soil temperatures and prevents damage to new shoots that may have formed beneath the mulch. Once the protective materials are cleared, inspect the canes for winter damage, which appears as black or dark brown discoloration. Prune these damaged canes back to where the pith, or inner core, is a healthy white or green color.