Pampas grass (Cortaderia selloana) is known for its towering stature and hardy nature, but its winter appearance can be alarming when the massive, feathery plumes turn uniformly brown. Determining whether the plant is merely resting for the season or has truly perished requires a few physical checks. This guide provides the diagnostic tools and recovery steps necessary to assess the condition of your pampas grass.
Is It Dormant or Dead?
Pampas grass naturally enters winter dormancy, causing its above-ground foliage to turn dry and tan, often appearing completely dead. This protective mechanism allows the plant to conserve energy and survive cold temperatures. The difference between a dormant plant and a dead one lies in the condition of the crown and roots, which must be physically examined.
The most reliable method for clumping grasses is the “tug test” on a handful of the brown blades near the base. If the grass resists your pull, remaining firmly anchored to the ground, it indicates the root system is alive and the plant is merely dormant. Conversely, if the brown foliage pulls away easily with little to no resistance, it suggests the roots have failed and the plant is dead.
A second inspection involves looking deep into the crown, the base of the plant. A healthy, dormant crown will be firm to the touch, potentially showing a pale, cream, or white color at the center. If the crown tissue is mushy, spongy, or has turned a dark brown or black, it points to severe root or crown rot, which is often fatal.
Common Reasons for Decline
Decline outside of winter dormancy is often related to improper maintenance or environmental stress that compromises the crown. A frequent issue is the development of a dense, heavy thatch layer from unpruned old growth, which prevents sunlight and air from reaching the center. This heavy accumulation of dead material can suffocate emerging new shoots, leading to die-out in the middle of the clump.
The tight growth of older clumps also creates conditions that encourage crown rot, especially in locations with poor drainage. As the plant ages, the center becomes compacted, trapping excessive moisture around the rhizomes. This constant saturation leads to the breakdown of the plant’s core, which is often the reason for the common “doughnut” pattern of growth where only the outer ring of the clump remains alive.
While the plant is hardy, extremes in moisture can cause stress. Established pampas grass is drought-tolerant, but newly planted specimens need consistent moisture to establish a robust root system. A prolonged drought can cause mature plants to enter survival mode, leading to excessive browning and a weakened state.
Essential Recovery and Care Steps
Aggressive annual pruning is essential for reviving and maintaining pampas grass, and should be performed in late winter or early spring before new growth appears. Cut the entire clump down to a height of 6 to 12 inches above the ground, using long-handled loppers or a reciprocating saw for larger plants. This hard cut removes the old, stifling thatch and clears the way for vigorous new foliage; always wear protective gloves and long sleeves as the leaves are sharp.
Following the cutback, you can apply a balanced, slow-release fertilizer, such as an 8-8-8 or 10-10-10 formula, to give the new growth a boost. Avoid using high-nitrogen products, as this can encourage excessive foliage growth at the expense of the signature plumes. For established plants, fertilization may be unnecessary unless the soil is very poor.
Watering practices should be adjusted to the plant’s age and environmental conditions. Ensure new plantings receive deep, consistent watering until their root systems are fully developed. The best practice for all pampas grass is to water deeply and infrequently, allowing the soil to dry out between applications to prevent the crown rot that causes central die-out.
If an older clump has developed the characteristic dead center, rejuvenation requires division. This process involves digging up the entire clump and using a sharp spade or axe to cut away the dead, interior sections of the crown. Dividing the plant every few years prevents central die-out and allows you to replant the healthy, vigorous outer sections.