First, you must understand my fundamental needs. I am a Mediterranean herb, which means I am genetically programmed for hot, dry summers and mild, damp winters. My woody stems and small, hairy leaves are adaptations to conserve water. My greatest threat in a cold climate is not the air temperature itself, but the combination of cold and wet, frozen soil. This combination can lead to two fatal conditions: root rot from soggy, non-draining soil, or desiccation where my roots are frozen and cannot take up water, while winter winds pull moisture from my leaves.
As the days shorten and temperatures drop, I receive the signal to enter a state of dormancy. My growth will slow and eventually halt to conserve energy. Your help at this stage is crucial. Please cease fertilizing me by mid-fall, as new, tender growth is highly susceptible to frost damage. You should also reduce watering significantly. My soil should be allowed to dry out more between waterings to prevent the cold, wet conditions that my roots find so intolerable. A light trim after the first hard frost is beneficial; remove any dead or overly long growth, but avoid a harsh, heavy pruning that would stimulate new growth.
For me to survive in the ground, my crown (the central point where my stems meet the roots) must be protected. After the ground has frozen hard, apply a thick, loose layer of mulch around my base. Excellent materials include straw, pine boughs, or shredded leaves. This layer does not keep me warm; rather, it keeps the ground consistently frozen, preventing the destructive cycle of freeze-thaw-freeze that can heave my roots right out of the soil. It also acts as a blanket against bitter, drying winds. For potted plants like me, the situation is more dangerous as our roots are exposed on all sides. The best solution is to move my container to an unheated but protected location like a garage, shed, or cold frame where the temperature stays consistently cold but above freezing.
Once I am dormant and properly insulated, my needs are simple. I require minimal to no water, especially if I am in the ground and covered by snow, which provides perfect natural insulation and moisture. If I am in a protected location and the soil becomes bone-dry, a very slight watering at the base on a day when temperatures are above freezing may be necessary to prevent total desiccation, but this is rarely needed. The goal is to keep my roots just moist enough to survive without encouraging any activity.
As the sun strengthens and daytime temperatures become consistently warmer, you can begin to gently remove the winter mulch. Do this gradually to allow me to acclimate and to protect me from a surprise late frost. Once you see definite signs of new green growth emerging from my base, you can carefully prune away any dead, woody stems from the previous year. This is also the time to resume regular, moderate watering and, eventually, a light feeding to support my new season of growth.
