Succulents are drought-tolerant plants that store water in their leaves, stems, or roots. Although often perceived as slow-growing, most succulents do spread through lateral growth. This expansion relies on asexual, vegetative propagation, creating genetic clones of the parent plant. The methods and speed of this spread vary significantly between species, determining how much space a succulent will ultimately occupy.
Biological Mechanisms for Lateral Growth
The lateral expansion of a succulent primarily occurs through the specialized development of new growth points. The most common mechanism is the production of offsets, often referred to as pups or plantlets, which are miniature clones growing directly from the base or stem of the mother plant. These new growths are initially sustained by the parent but eventually develop their own independent root systems, allowing them to be separated for propagation.
Another significant method involves specialized horizontal stems known as runners or stolons. These stems grow above the soil surface and produce a new, fully-rooted plantlet at the nodes, effectively “running” across the ground. Groundcover species of Sedum and Sempervivum frequently employ this strategy to rapidly colonize a wide area. Trailing varieties utilize stem rooting, where elongated stems develop adventitious roots when they make contact with the soil.
Furthermore, some succulents spread when leaves or segments of the stem detach easily upon disturbance. These fallen pieces of plant material contain the necessary tissue to callus over and root independently, creating entirely new plants. This ability to clone from small fragments is a highly effective way for the plant to propagate itself across a landscape.
Understanding Different Spreading Habits
The physical manifestation of a succulent’s reproductive strategy results in distinct growth patterns that are important for gardeners to recognize. Mat-forming or groundcover succulents are the most aggressive spreaders, using runners and rooting stems to create a dense, low carpet of foliage. Examples include Sedum spurium and Senecio mandraliscae, which can quickly cover large areas in outdoor plantings.
In contrast, clumping or tight-growing species spread slowly and locally through the continuous production of offsets around the central rosette. Plants like Echeveria and Haworthia form dense clusters, where the pups remain closely attached to the parent, resulting in a tight, mounded appearance. This habit causes the plant to increase in girth rather than length, leading to a crowded pot over time.
Other succulents exhibit a trailing or draping habit, where their stems grow downward over the edge of a container. Popular hanging basket varieties like Senecio rowleyanus spread by lengthening their stems, which will root if the strands touch the soil. On the opposite end of the spectrum are non-spreading or solitary succulents, such as the Agave and Lithops genera, which typically remain as a single rosette and rarely produce offsets.
Controlling and Utilizing Succulent Spread
Since many succulents reproduce vegetatively, controlling their spread involves either containing the lateral growth or actively utilizing the new plantlets.
Containing Lateral Growth
For ground-planted varieties that spread via runners, a physical barrier, such as a buried strip of plastic edging, can effectively limit expansion. For container plants, simply ensuring the pot is not sitting directly on the ground prevents trailing stems and pups from rooting into the surrounding landscape.
Division and Repotting
To maintain a plant’s health and shape, the process of division is necessary, which involves safely separating the offsets from the parent. For pups growing on a runner, a clean cut with a sterilized blade is used to sever the connection to the mother plant. The separated plantlet should be allowed to dry and form a protective callus over the cut end for several days before being potted into fresh, well-draining soil.
Pruning Trailing Varieties
Trailing succulents benefit from selective pruning, which serves to manage their length and encourage a bushier appearance near the crown. A stem can be trimmed by making a clean cut just above a leaf node, which stimulates the growth of new side shoots at that point. The severed stems can then be easily utilized as cuttings for propagation, effectively turning an act of maintenance into an opportunity to multiply the collection.