Pampas Grass (Cortaderia selloana) is a large, ornamental perennial grass prized for its dramatic, feathery plumes. Its presence in a landscape is defined by its seasonal cycle, which dictates when it offers its greatest visual impact and when it requires active care. Understanding the timing of its aesthetic peak, active growth, and dormancy is important for gardeners aiming to maximize its showy appearance and ensure the plant remains healthy.
The Prime Flowering Cycle
The peak aesthetic season for Pampas Grass begins in the late summer and extends well into the fall, when its characteristic plumes emerge. These towering flower stalks create a striking focal point in the landscape. The emergence of the plumes is triggered by the natural shift in daylight hours and temperatures signaling the end of the summer growing period.
Initial plumes typically appear around August or September, starting as dense, upright panicles that rise significantly above the arching foliage. These fresh plumes can range from silvery-white to pale pink, depending on the cultivar. Female plants generally produce the showier, fuller plumes.
The plumes mature and dry out on the stalk, transforming into a fluffy, tan or golden-brown color. This dried appearance allows them to persist throughout the winter months, providing structure and texture to the dormant garden. The plumes remain attractive until they are removed by severe weather or pruning in the spring. Full-sun exposure helps maximize the production of these spectacular flowering stalks.
Seasonal Maintenance Timing
Necessary maintenance occurs outside of the peak flowering season, primarily during winter dormancy. The most significant yearly task is a hard pruning, timed for late winter or very early spring, generally between February and April. This timing ensures the cutback happens after the harshest weather has passed but before the new foliage begins its strong spring growth.
Leaving the old foliage and plumes intact throughout the winter offers natural protection for the plant’s crown against freezing temperatures. Pruning too early in the fall can expose the central growth point, making it vulnerable to frost damage. The late winter cutback removes all the previous year’s growth down to about 6 to 12 inches above the ground, making way for fresh, green shoots.
Division of mature clumps is another periodic task, done every few years to rejuvenate the plant and manage its size. This process is also best performed in the spring, just as new growth is beginning. Spring division allows the separated sections an entire growing season to establish a robust root system before the next winter.
Planting and Establishment Timing
Planting or propagation is optimally timed to align with the plant’s active growth phase. The best window for planting nursery-grown specimens is in the spring, after the last threat of frost has passed, generally from April through mid-June. Planting during this time allows the roots to establish themselves firmly in the warming soil before the onset of summer heat or winter cold.
A newly planted specimen will not immediately produce large, showy plumes, as it requires a period of establishment before flowering. Pampas Grass grown from seed or a young transplant typically needs two to three years to reach sufficient maturity and size to produce its first plumes.
This establishment period is a prerequisite for the visual spectacle of its prime season. Spring planting gives the young plant the longest possible time to develop a strong root system, increasing its chances of survival and reliable flowering in subsequent years. Starting seeds indoors in early spring, such as February to April, provides seedlings a head start for later transplanting outdoors.