Mexican Feather Grass (Nassella tenuissima) is a popular ornamental grass that introduces soft movement to gardens. This perennial bunchgrass forms dense, fountain-like mounds that sway gracefully even with the slightest breeze. Understanding the mature size of this plant is important for landscape planning, as its final dimensions are influenced by both its genetics and its environment. This article focuses on the typical size of Mexican Feather Grass and the conditions that determine how tall it will ultimately grow.
Typical Height and Spread
Mexican Feather Grass generally maintains a manageable size, making it a favorite for borders and containers. The typical mature height for a healthy, established clump ranges from about 1 to 2 feet, or 30 to 60 centimeters. This measurement includes the fine, silvery-green foliage, which transitions to a characteristic golden-tan color as the season progresses.
The plant’s width, or spread, is usually similar to its height, creating a balanced, rounded tussock shape. While most plants stay within the 1-to-2-foot range, under ideal conditions, some may reach up to 3 feet tall when the wispy flowering panicles are included. The plant’s overall size is defined by the tight, clump-forming structure of its base.
Environmental Factors Affecting Growth
The ultimate height and structural integrity of Mexican Feather Grass are dependent on its growing environment. This plant is naturally adapted to arid regions and thrives in full sun, which encourages a shorter, more compact form. Planting the grass in partial shade can result in leggier, less dense growth as the foliage stretches to seek light.
Soil quality is a major determinant of size, as the plant prefers lean, well-draining, and even rocky or poor soils. When grown in rich, fertile soil or subjected to over-fertilization, the growth rate increases rapidly. This excessive growth can weaken the plant’s cell structure, leading to “lodging,” where the grass grows taller than usual but then flops over. Excessive watering can also push the plant past its typical size.
Pruning for Size Management
Maintaining the desired size and appearance of Mexican Feather Grass requires a specific, annual pruning technique. Since the plant is a cool-season grass, it accumulates dead, dormant foliage throughout the winter. This old growth must be removed to allow new, vibrant green shoots to emerge unhindered in the spring.
The necessary maintenance involves a hard cutback, performed in late winter or very early spring before new growth begins. Gardeners should cut the entire clump down to a height of about 3 to 6 inches above the crown. This severe cut prevents the mixing of old, straw-colored blades with the fresh green growth, ensuring a tight, renewed clump.