Hebes are popular evergreen shrubs native to New Zealand, prized for their year-round foliage and colorful, spire-like flowers. While common in temperate gardens, their ability to withstand cold weather is frequently questioned. Whether Hebes “die back” in winter depends heavily on the specific variety planted and the severity of local climate conditions. Although most are evergreen, deep or prolonged freezes can cause significant damage or fatal dieback.
Understanding Hebe Hardiness by Variety
The ability of a Hebe to tolerate winter temperatures is highly variable, rooted in the diverse alpine and coastal origins of the species in New Zealand. While many Hebes are comfortable in USDA hardiness zones 7 through 10, the range of cold tolerance is extensive. The size of the plant’s leaf is a reliable indicator of its cold resilience. Smallest-leaved varieties, such as the compact, whipcord types like Hebe cupressoides and Hebe pinguifolia ‘Sutherlandii,’ are typically the hardiest, sometimes surviving temperatures down to 0°F.
These hardier, small-leaved types often originate from high-altitude regions and possess adaptations that help them endure colder conditions. Conversely, many larger-leaved, more ornamental Hebe cultivars are significantly more tender and suffer damage when temperatures drop below 20°F. These vulnerable types are often treated as temporary annuals or container plants in regions with cold winters. Even within a suitable hardiness zone, a plant’s microclimate can override its inherent cold tolerance. Exposure to harsh, drying winter winds or planting in poorly drained soil can severely compromise a Hebe’s ability to survive.
Identifying Winter Damage and Stress
When winter conditions become stressful, Hebes can display a range of symptoms. A common, non-fatal reaction to cold is the bronzing or purpling of the foliage as the plant alters its internal chemistry for protection. Mild leaf browning, wilting, or some leaf drop may simply be signs of temporary stress or dormancy, which the shrub usually recovers from completely in the spring. It is important to distinguish this temporary discoloration from more serious damage that leads to permanent loss of plant tissue.
More serious frost damage manifests as blackening of the leaves and stems, a mushy texture in the foliage, or splitting bark on the main woody stems. These symptoms indicate that the tissue has been fatally compromised by freezing temperatures. To assess the damage, gardeners can perform a simple “scratch test” by gently scraping bark from a branch. Finding green tissue immediately beneath the bark confirms the branch is alive and capable of recovery. Brown or dry tissue indicates that section is dead, and it is generally best to wait until late spring to prune severely damaged Hebes.
Practical Steps for Winter Protection
Protecting Hebes from winter damage begins with thoughtful site selection, as harsh conditions can stress even the most resilient varieties. Planting Hebes in a sheltered location, such as near a wall or alongside other shrubs, helps shield them from prevailing winter winds and damaging desiccation. Avoid sites where the morning sun strikes the plant immediately after a hard frost, as this rapid thawing can rupture frozen cells and cause tissue death.
Soil conditions are equally important, as Hebes will not thrive in wet, waterlogged ground, especially when cold. Ensuring the planting area has excellent drainage is paramount, since cold, saturated soil promotes root rot and reduces cold tolerance. Gardeners should also avoid fertilizing Hebes late in the season, as this encourages soft, new growth highly susceptible to frost damage.
Physical protection methods provide an additional layer of insulation for plants in the ground. Applying a thick layer of organic mulch, such as bark chips or straw, around the base helps insulate the roots from extreme cold. For borderline hardy varieties or during periods of severe, sustained cold, temporary covers can be used. Covering the shrub loosely with horticultural fleece or a blanket provides protection, but must be removed once the extreme cold spell passes. Container-grown Hebes are particularly vulnerable and should be moved to a sheltered spot, like an unheated garage or porch, for the winter.