Sedum, commonly known as Stonecrop, is a diverse genus of succulent plants valued in landscaping for its hardiness and drought tolerance. The rate of spread is highly variable, depending almost entirely on the specific growth habit of the variety chosen. Understanding the physical mechanics of growth is the first step in predicting how quickly Stonecrop will cover an area.
Growth Habits of Sedum Varieties
The rate and pattern of spread are determined by which of the two major categories a Sedum belongs to. Creeping or trailing Sedum varieties are the groundcover types that actively spread outward. These species, such as Sedum spurium or Sedum acre, develop horizontal stems that root wherever they make contact with the soil. This allows them to form a dense, continuous mat of foliage across the ground surface, making them effective groundcovers.
The second category is the clumping or upright Sedum, which includes popular cultivars like ‘Autumn Joy’ (Hylotelephium). These plants grow vertically from a central crown and increase only by slowly expanding the size of the original clump. Upright varieties do not produce the rooting stems or runners that allow groundcovers to colonize new territory quickly. Their spread is limited to a gradual increase in the diameter of the central root ball, rather than a rapid outward expansion.
Quantifying the Rate of Spread
For the fast-growing, groundcover types, the spread can be significant. Many creeping Sedum varieties can expand their footprint by 6 inches to 1.5 feet per year under optimal conditions. This growth rate means a single small plant can sprawl to cover an area of up to three feet wide within a few growing seasons.
The spread is often non-linear due to fragmentation. Sedum stems and leaves are highly adapted to propagate, meaning even small pieces that break off and fall onto the soil can easily root and establish a new, independent plant. This self-propagation by dropped fragments can lead to a dense, sometimes unpredictable colonization of adjacent areas. Consequently, the actual rate of coverage often exceeds the measured extension of the original plant’s main stems.
Environmental Factors Affecting Growth Speed
The speed of Sedum spread is influenced by the conditions of its planting environment. Sedum plants thrive and spread fastest when they receive at least six hours of direct sunlight each day. Insufficient light reduces the plant’s energy production, causing stems to stretch and become thin, known as “legginess,” which slows the dense, outward growth desired for groundcover.
The composition of the soil also plays a significant role in determining the plant’s vigor and density. Sedum prefers lean, rocky, or average soil that drains sharply, as this mimics its native, arid environment. Soil that is too rich or overly fertile, such as heavy clay or heavily amended garden beds, can lead to excessive, weak growth that causes the stems to flop over, rather than spreading firmly.
While Sedum is exceptionally drought-tolerant once established, consistent moisture during the first year accelerates the rate of establishment and outward expansion. Newly planted Sedum requires moderate, regular watering until its root system is fully developed to support rapid stem growth. After this initial period, reduced watering encourages the robust, drought-resistant habit for which the plant is known.
Techniques for Managing Sedum Spread
Containing Spread
Managing the spread of Sedum involves either encouraging faster coverage or containing a variety. To contain vigorous creeping types, using physical barriers like edging or rocks set into the soil can define the planting area’s boundaries. For groundcovers that spill over pathways, simply trimming the stems back to the desired edge will maintain a neat appearance.
Encouraging Density and Division
Upright and clumping varieties can be managed by dividing the main clump every three to five years, especially when the center begins to die out or the overall size becomes too large. This maintenance task involves digging up the entire plant and separating it into smaller sections to replant.
Conversely, to encourage a dense groundcover mat, stem fragments or cuttings can be intentionally broken off and laid directly onto the soil surface. These fragments will readily root and contribute to faster, denser coverage across the intended area.