Wrapping certain hydrangeas for winter protection is necessary because of the plant’s unique blooming characteristic. Varieties like the large-leaf mophead and lacecap (Hydrangea macrophylla and Hydrangea serrata) produce flower buds on the previous year’s growth, known as “old wood.” These tender buds are susceptible to damage from extreme cold, fluctuating temperatures, and desiccating winter winds, especially in colder climates (USDA Hardiness Zones 5 and 6). If temperatures drop below 15°F, these buds can freeze and die, resulting in few or no flowers the following summer. The purpose of wrapping is to create a protective microclimate that shields these delicate buds, ensuring they survive the winter to produce blooms the following season.
Prepping the Hydrangea for Winter Protection
Preparation should occur after the plant enters dormancy but before the ground freezes solid. Optimal timing is typically after the first few hard frosts in late fall, which signals the plant to harden off its tissues. Before wrapping, thoroughly hydrate the plant, as well-watered stems are more resilient to the drying effects of winter cold and wind. Deep watering ensures the root ball has sufficient moisture reserves to sustain the plant through dormancy.
After deep watering, apply a substantial layer of mulch directly around the crown of the plant. This layer, ideally six to twelve inches deep, insulates the roots and the base of the stems from severe temperature swings. Suitable materials include shredded bark, pine needles, or dry, shredded leaves, which provide insulation while allowing air circulation. Applying this heavy mulch layer after the ground has slightly frozen also discourages rodents from nesting near the plant crown.
Necessary Materials for the Protective Structure
Building an effective protective structure requires specific items to ensure both insulation and stability. Sturdy wooden or metal stakes, such as T-posts or bamboo poles, are needed to establish the framework around the shrub. These stakes provide the necessary support for the insulation and outer wrapping, preventing the structure from collapsing under the weight of snow or wind. The structural perimeter is created using flexible material like chicken wire or wire fencing, which forms the protective cage around the hydrangea.
The inner filling material, which provides the actual insulation, must be loose and dry. Excellent choices include straw, marsh hay, or large volumes of dried, non-compacting leaves, such as oak leaves. A breathable outer layer, typically burlap or similar horticultural fabric, is needed to wrap the entire cage. Durable twine, zip ties, or heavy-duty staples are used to securely fasten the wire fencing and the outer burlap layer to the stakes.
Detailed Steps for Insulation and Wrapping
The process begins by establishing a support cage that completely encircles the hydrangea. This cage should be positioned six to twelve inches away from the outer branches. Drive four or more sturdy stakes into the ground around the plant, ensuring they stand taller than the shrub. Wrap the wire fencing around these stakes to create a cylindrical or square enclosure, securing the ends tightly with twine or zip ties.
Next, fill the space around the hydrangea canes with loose insulating material. Gently pack straw or dried leaves into the cage, completely surrounding the stems and covering the old wood buds. It is important to avoid compacting the material tightly, as this traps moisture and restricts crucial air circulation. Restricted airflow can lead to fungal issues, so the filling must remain loose. The filling must reach the top of the cage to ensure the uppermost flower buds are protected.
The final step involves applying the outer layer of breathable burlap. Wrap this fabric around the entire circumference of the wire cage; it acts as a windbreak and protects the dry insulation from soaking rain or snow. Fasten the burlap securely to the stakes and wire using twine or staples to prevent it from being ripped away by strong winter gusts. To prevent water saturation, a cap made of plywood or Styrofoam can be placed loosely over the top, ensuring air can still move freely around the edges.
When and How to Uncover in Spring
The timing for removing the protective structure is determined by the local climate and the disappearance of hard frost threats, typically in early to mid-spring. Wait until the danger of sustained freezing temperatures has reliably passed. Removing the protection too early subjects the newly insulated growth to a sudden temperature shock or a late-season freeze.
Removal should be executed gradually to allow the canes to re-acclimate to ambient conditions. Carefully take down the outer burlap and remove the wire cage, then gently pull the insulating material away from the stems. Perform this task on a cloudy day to prevent the tender, shade-grown buds from being scorched by bright sunlight. The heavy mulch layer around the crown should also be pulled back slightly to permit the soil to warm and allow new shoots to emerge unobstructed.