Rosemary, Salvia rosmarinus, is a woody perennial shrub that often survives winter and returns in the spring. Survival depends heavily on the local climate and the care it received before and during the cold months. As an evergreen, rosemary attempts to keep its foliage all year, but it is not immune to frost and cold damage. If the root system and lower woody stems remain undamaged, the top growth can regenerate when warmer weather arrives.
Rosemary’s Perennial Nature and Hardiness
Rosemary is native to the Mediterranean region, characterized by mild, wet winters and hot, dry summers. This explains its preference for well-draining, sandy soil and its intolerance for prolonged, deep freezing temperatures. Its woody stems develop a hard, bark-covered structure, allowing it to persist for many years.
The main factor determining survival is the severity and duration of cold temperatures. Most rosemary varieties are hardy down to about 20°F, though some cultivars like ‘Arp’ tolerate temperatures as low as 5°F with protection. Demise often results from cold exposure combined with excessive moisture in the soil. Soggy, frozen roots are more susceptible to rot than dry ones, which is the primary reason the plant fails to revive.
How to Determine if the Plant is Still Alive
When spring arrives and your rosemary appears brown and lifeless, a simple diagnostic process can confirm its condition. The most reliable method is the scratch test, which involves lightly scraping the outer bark of a stem with a fingernail or small knife. If the tissue immediately beneath the bark is bright green and moist, that section of the plant is still alive. A brown, dry, or brittle layer indicates dead wood.
Begin this test on the smaller, upper branches and work your way down the main stems toward the base. Often, a plant appears dead at the tips but still has living tissue near the soil line, indicating a chance for recovery. Another simple test is the flexibility test: live wood will be pliable and bend easily, while dead wood snaps cleanly with little effort.
If all visible stems are brittle and brown, gently check the roots, especially in container plants. Healthy rosemary roots are firm and light-colored. Dark, mushy, or foul-smelling roots indicate significant root rot, meaning the plant has likely died. Remember that rosemary is one of the last herbs to show new growth in the spring, so patience is necessary before declaring the plant lost.
Encouraging Regrowth After Damage
Assuming the diagnostic tests reveal living green tissue, the next step is to remove all dead material. Use sharp, sterilized pruning shears to cut back dead stems just above the first sign of green tissue. Removing this dead wood stimulates the plant to focus energy on producing new growth from viable stems and buds below.
After pruning, careful water management is the most important recovery step. Since cold damage often occurs with wet conditions, the soil must dry out significantly between waterings. Overwatering a stressed rosemary will guarantee the onset of root rot.
Place the plant in a location with maximum sun exposure, ideally six to eight hours of direct light daily. For container-grown rosemary, relocating it to a sheltered spot that still receives full sun protects the recovering roots from sudden temperature fluctuations. Wait to apply fertilizer until you see definite signs of new, active growth, as feeding a stressed plant can cause further harm.