Pampas grass (Cortaderia selloana) is a large, ornamental perennial grass highly valued in landscaping for its dramatic size and feathery plumes. This South American native forms impressive, dense clumps. Because its appearance changes significantly during winter, property owners often wonder about its survival and the timing of its return in the warmer months.
Understanding Winter Dormancy
Pampas grass is not dead when its foliage turns brown and dry during the winter; it is merely dormant. This perennial plant slows its metabolic processes to conserve energy, storing resources in a dense underground structure called the root crown. This mechanism allows the grass to survive freezing temperatures and harsh conditions.
In warmer regions, typically USDA Hardiness Zones 9 and above, pampas grass may remain evergreen with only minimal browning. In colder areas, the plant’s above-ground growth dries completely, turning a tan color. This old foliage provides a layer of insulation for the root crown against extreme cold, allowing the plant to rebound vigorously when conditions improve.
Key Environmental Factors Driving Spring Growth
The primary signal for pampas grass to begin its spring growth cycle is the warming of the soil, which lags behind air temperature. As a warm-season grass, Cortaderia selloana requires sufficiently warm soil temperatures to trigger metabolic activity and break dormancy. Growth accelerates noticeably when soil temperatures consistently rise above 55°F (13°C) at the root level.
The timing of this soil warming varies significantly by climate zone. Gardeners in warmer areas (Zones 8 through 10) may see new growth as early as late February or March. Conversely, in colder climates (Zones 6 and 7), the ground takes longer to thaw, pushing the emergence of new shoots back until mid-to-late April or early May.
Fluctuations in spring weather can influence the visible return of the grass. A sudden late-season frost can temporarily halt the growth of emerging shoots or damage tender new foliage, delaying the plant’s full re-establishment. The plant waits for consistent warmth, rather than just a few warm days, before committing its stored energy to new growth.
Essential Preparation for Regrowth
The annual cutback of the previous year’s foliage precedes visible regrowth. This task is performed in late winter or early spring, ideally just before the first signs of new life. Removing the dead material permits sunlight and air circulation to reach the crown, which stimulates the healthiest, densest new growth.
Pruning should be done drastically, cutting the entire clump back to a height of about 6 to 12 inches (15 to 30 cm) above the ground. Cutting the foliage back in autumn is not recommended because the hollow stems can collect water, potentially leading to crown rot and increased susceptibility to frost damage over winter.
Safety precautions are important during the cutback process due to the razor-sharp edges of the leaves. Gardeners should always wear sturdy, cut-resistant gloves, long sleeves, and eye protection to prevent cuts and abrasions. This maintenance prevents the older, dead material from stifling the emerging spring shoots.
Identifying the First Signs of Life
The return of the pampas grass is visually confirmed by the emergence of bright green shoots from the center of the plant. This new growth appears from the root crown, often referred to as the eyrie. These new tillers are typically tightly rolled and sharp, contrasting starkly with the dry, brown foliage from the previous year.
Gardeners can begin to check for these signs once the risk of severe frost has passed and the spring warm-up is well underway. The new shoots may reach a length of 4 to 6 inches (10 to 15 cm) before the old material is fully cut away. The appearance of these healthy, vibrant green tillers confirms the plant is ready for the new growing season.