The genus Sedum, commonly known as Stonecrop, includes a vast collection of succulent perennial plants. These plants store water in their fleshy leaves and stems, allowing them to thrive in dry conditions. Determining how tall Sedum grows is complicated because the genus contains hundreds of species, with mature sizes ranging from a few inches to several feet. To accurately determine a Stonecrop’s potential size, one must first identify its growth habit, as this dictates its ultimate vertical reach.
Understanding the Two Main Growth Habits
Sedum species are broadly categorized into two distinct growth forms: upright and creeping. Upright varieties, often reclassified into the genus Hylotelephium, form dense, clumping mounds with sturdy, vertical stems. These plants are grown for their substantial presence and late-season flower heads, making them ideal for perennial borders.
Creeping Sedum exhibits a low, mat-forming habit, spreading laterally across the ground. Their growth focuses on creating a dense carpet of foliage, measured primarily by its spread rather than height.
Specific Height Ranges of Upright Varieties
Upright Sedums are the tallest members of the genus, providing significant vertical structure in the late-season garden. These varieties develop strong, thick stems that terminate in large, dome-shaped or flat-topped flower clusters. Their mature height generally falls between 18 inches and 3 feet (45–90 centimeters), depending on the specific cultivar.
Classic cultivars like ‘Autumn Joy’ consistently reach 20 to 24 inches (50–60 cm) with a similar spread, forming a substantial clump. Taller selections, such as ‘Matrona,’ often grow up to 30 inches (76 cm) on rigid, deep-colored stems. These Stonecrops are commonly used in the middle or back of a garden border, where their height provides a backdrop for smaller plants.
Height and Spread of Creeping Varieties
Creeping Sedums are cultivated for their low-profile, ground-covering habit rather than their height. These varieties rarely exceed half a foot in vertical growth, even including the flower stalks. The foliage typically forms a dense mat only 2 to 6 inches (5–15 cm) tall, which sharply contrasts with upright types.
For these low-growing plants, the horizontal spread is the more relevant measurement, often reaching several feet wide. Cultivars such as ‘Angelina’ and ‘Dragon’s Blood’ are vigorous spreaders, with a single plant capable of covering 15 to 30 inches (38–76 cm) wide. Their low, dense growth makes them excellent choices for rock gardens, green roofs, and planting between stepping stones.
Environmental Factors Influencing Final Height
The genetic potential for height in any Sedum can be altered by its growing environment. Sunlight is a primary factor, as insufficient light causes the plant to stretch, a phenomenon known as etiolation. If Sedum does not receive the full sun it requires, its stems lengthen unnaturally to seek light, resulting in a taller but weaker and leggier plant that often collapses.
Soil richness and moisture levels also impact the final height and structural integrity of upright varieties. Plants grown in overly rich soil or provided with excessive water tend to grow too quickly and produce lush, soft growth. This rapid, weak growth frequently results in “flopping,” where the stems become top-heavy with flowers and buckle under their own weight.
Conversely, planting Sedum in lean, well-drained soil and minimizing irrigation encourages a shorter, sturdier, and more self-supporting structure. Gardeners can manage the height of upright Sedum through strategic pruning. The “Chelsea Chop” is a technique where stems are cut back by about one-third in late spring or early summer. This process temporarily reduces the plant’s height and removes apical dominance, encouraging multiple side shoots. This results in a bushier, shorter plant with more numerous flower heads that are less prone to flopping.