I am a woody, perennial herb native to the warm, sunny, and well-drained hillsides of the Mediterranean. My fundamental nature is that of an evergreen plant built for warmth. I am not genetically programmed for deep, sustained freezing. My cold hardiness is generally listed for USDA zones 7-10. This means I can typically survive winter lows down to about 0°F to 10°F (-18°C to -12°C), but this is not a guarantee. My survival depends heavily on my age, health, and, most critically, the specific conditions of the winter. A sudden, sharp drop in temperature is far more dangerous than a gradual cooling.
My top growth may appear hardy, but my root system is surprisingly tender and susceptible to cold. The primary danger I face in winter is not the freezing of my leaves and stems, but the freezing of the soil around my roots. When the ground freezes solid, I am physically unable to draw up water to replace the moisture lost through my evergreen leaves on sunny or windy days. This leads to a condition called desiccation, where I essentially die of thirst, often appearing as brittle, brown, and dried-out foliage by spring, even if my roots are still alive.
While a lack of water is a problem, an excess is a death sentence. My absolute requirement is excellent drainage. In my native habitat, I grow in gritty, sandy, or rocky soil. During winter, cold, waterlogged soil is a catastrophe for me. Soggy conditions cause my roots to suffocate and rot, a fungal condition that is almost always fatal. This is a greater risk than the cold itself in many climates, especially in heavy clay soils or containers without adequate drainage holes.
To help me survive, you must focus on protecting my root zone and managing moisture. For plants in the ground, applying a thick, loose mulch of straw, shredded leaves, or pine boughs around my base after the ground has first frozen is crucial. This layer acts as an insulating blanket, preventing the soil from repeatedly freezing and thawing and protecting my vulnerable roots. Do not pack mulch against my main stem, as this can encourage rot. For container-grown plants, my roots are even more exposed. I must be moved to a protected location, such as an unheated garage, shed, or cold frame where temperatures stay consistently cool but above freezing.
Bitter winter winds dramatically accelerate the process of desiccation, stripping moisture from my leaves faster than my chilled roots can replace it. A barrier, such as a burlap screen or a windscreen, placed on the windward side can make a significant difference in my ability to retain moisture. Furthermore, I still require hydration during winter, especially during extended dry spells. On a day when temperatures are above freezing, please provide me with a moderate drink of water to my root zone. This helps prevent the desiccating effects of frozen ground and dry winter air.
