Pampas grass, known scientifically as Cortaderia selloana, is a large, perennial ornamental grass native to the grasslands of South America. It grows in dense, fountain-like clumps of foliage. The plant is recognized for its impressive, feathery flower plumes, which create a striking visual display. Because of its bold texture and ability to thrive in various environments, pampas grass remains a popular choice for gardeners seeking a low-maintenance, high-impact plant.
Maximum Height and Growth Rate
The full-sized variety of pampas grass is known for its rapid growth and imposing stature. The foliage, composed of long, arching, gray-green leaves, typically forms a dense tussock reaching 6 to 10 feet high. These clumps can also spread significantly, often reaching a width of 4 to 8 feet at maturity.
The plant’s true height is measured when the flower stalks, or plumes, emerge in late summer. These plumes rise well above the basal foliage, adding another 2 to 3 feet to the overall height. Under optimal growing conditions, a mature specimen with plumes can easily reach a total height of 12 feet, with some exceptional reports of plants nearing 15 feet.
Pampas grass is a fast-growing perennial that can add several feet of growth in a single season once established. While established plants reach their seasonal height quickly, reaching full maturity from seed takes longer. Plants grown from seed generally require two to four years to achieve maximum size and begin producing plumes.
Factors Influencing Mature Size
The final height of pampas grass is influenced by both genetic and environmental variables. Cultivar selection is the most significant genetic factor dictating mature size. The standard species, Cortaderia selloana, is the largest, while cultivars like ‘Sunningdale Silver’ often reach about 10 feet.
Gardeners looking for a smaller plant can select dwarf varieties, such as ‘Pumila,’ which is bred to be more compact. This cultivar typically grows to a manageable height of only 4 to 6 feet, making it suitable for smaller gardens or container planting. Another dwarf option, ‘Compacta,’ has flower stems that top out around 4 feet (120 cm).
Environmental conditions play a strong role in maximizing the plant’s height potential. Pampas grass prefers full sun for a minimum of six hours daily; insufficient sunlight can result in reduced plume size and less vigorous growth. While drought-tolerant once established, the plant thrives in rich, well-drained soil and benefits from consistent moisture during its initial growth phase.
Managing Tall Growth
Given the plant’s potential for significant height and spread, managing its placement is a practical consideration for landscape design. The foliage is sharp, possessing serrated leaf edges that can cause cuts, necessitating protective gear when handling. Due to its size and sharp foliage, it should be sited well away from high-traffic areas, such as walkways or patios.
To maintain a tidy appearance and encourage robust new growth, pampas grass requires annual hard pruning. This maintenance task is best performed in late winter or early spring before new growth begins. Gardeners should cut the entire clump back severely, typically to a height of 12 to 18 inches above the ground.
This yearly cut prevents the accumulation of dead material, which can increase the risk of fire and lead to a less attractive appearance. Proper siting also involves ensuring the plant has enough room to spread, typically requiring a dedicated space of 6 to 14 feet to prevent overcrowding.