The genus Sedum, commonly known as Stonecrop, is a large group of succulent plants celebrated for their hardiness and diverse forms. Determining the mature size of a Sedum depends entirely on the specific species or cultivar, as the genus encompasses hundreds of different plants. Size ranges dramatically, from varieties that form a thin, spreading mat over the ground to those that grow into substantial, shrub-like perennial clumps.
Categorizing Sedum by Growth Habit
The size variability within the Sedum genus is best understood by dividing the plants into two primary growth habits: creeping and upright. This categorization defines the plant’s structural purpose and its potential footprint in the garden.
Creeping Sedum varieties are low, mat-forming plants that spread horizontally. These species typically grow only one to six inches tall, staying close to the soil surface. Their primary function is as a living groundcover, often used in rock gardens or on green roofs. Their width can be substantial as they continuously spread outward by rooting along their stems.
Upright Sedum varieties (often classified as Hylotelephium) exhibit a vertical, clump-forming habit. They feature thick, fleshy stems that rise upward, culminating in dense flower heads in late summer and fall. Unlike creeping forms, upright varieties do not aggressively spread but form tight, manageable clumps, making them suitable for perennial beds and borders.
Detailed Size Profiles of Common Varieties
Creeping varieties are recognized for their low-profile spread. White Stonecrop (Sedum album) typically reaches a height of only two to four inches. While short, its spread can easily reach 12 to 24 inches wide, sometimes spreading indefinitely as it roots along the ground.
Goldmoss Stonecrop (Sedum acre) shares a similar low stature, often reaching only two to three inches in height. Its spread can cover a foot or more of ground, making it an effective living mulch. Low-growing forms are valued for their expansive coverage rather than vertical presence.
Upright forms are much more substantial. ‘Autumn Joy’ (Sedum spectabile) typically grows to a mature size of 18 to 24 inches tall and wide, forming a substantial clump.
Another upright cultivar, ‘Matrona’ (Sedum telephium), often exceeds this size, forming robust clumps that frequently reach heights of 24 to 30 inches. These taller varieties are distinct for their structural stability, providing a dense, mounding form.
Environmental Factors Influencing Mature Size
The size profiles listed for any Sedum variety represent its genetic potential, but external environmental factors determine the plant’s ultimate dimensions. Light exposure is one of the most significant factors influencing size. Sedum requires at least six hours of direct sunlight daily to maintain its dense, compact shape.
Insufficient light causes etiolation, where stems stretch rapidly toward the light source. This results in a taller but weaker and less structurally sound plant, often called “leggy” or “floppy.” While the plant achieves greater height, this growth is undesirable and may require staking.
Soil composition and water availability also influence size control. Sedum naturally thrives in lean, well-draining, poor soils, which limits growth and keeps the plant stocky. Conversely, planting Sedum in overly rich or heavily fertilized soil encourages excessive vegetative growth. This surplus of nutrients leads to taller, softer stems prone to breaking or collapsing under the weight of the flower heads.
An established Sedum plant generally reaches its mature size after two to three years of growth. Maintaining this size and vigor often involves regular division every few years, which prevents the clump from becoming overly large or dying out in the center. Providing the poor soil and low water conditions that mimic its native habitat ensures the Sedum remains true to its genetically determined size.