Growing moss between flagstones offers a distinctive, low-maintenance alternative to traditional joint fillers like sand or gravel. This practice softens the hard lines of a patio or walkway, creating a lush, aged aesthetic often associated with historic gardens. Moss naturally suppresses weed growth by competing for space, eliminating the need for frequent weeding and chemical treatments typically required to keep joints clear. Establishing a thriving moss carpet relies entirely on selecting the right location and species before moving to the physical act of planting.
Selecting the Environment and Species
Mosses are primitive plants lacking true roots, relying on constant moisture and shade. The primary requirement for success is a location that receives either full shade or filtered sunlight, as intense, direct sun will quickly desiccate and kill the moss. Mosses absorb water and nutrients directly through their leaves, so the area must retain moisture for them to photosynthesize and grow.
Choosing the appropriate moss type is important, generally falling into two categories. Acrocarpus mosses are upright and form dense, mounded cushions, making them excellent for a clumpy, textured look but are slower-growing and less tolerant of heavy foot traffic. Conversely, Pleurocarpus mosses are characterized by their creeping, mat-forming growth habit, branching freely and regenerating quickly from fragments. These mat-forming species are preferable for filling wide flagstone joints because they spread faster and establish a more uniform, walkable carpet. Specific varieties like sheet moss thrive in deep shade, while Bryum moss tolerates slightly more sun exposure.
Preparing the Installation Site
Before planting, the flagstone joints must be prepared to create an ideal substrate for the moss to colonize. Begin by thoroughly clearing out all existing organic material, including weeds, grass, and any loose joint filler like sand or gravel. Use a stiff brush or a narrow tool to scrape out the material, ensuring the joints are clear of competing plant life.
Moss requires a shallow, compact, and slightly acidic medium to anchor its tiny rhizoids. After cleaning, fill the empty joints with a thin layer of compacted substrate, aiming for a depth of at least half an inch. A mixture of soil, sand, and peat moss or aged compost works well, as this combination provides the necessary acidity, compaction, and moisture retention.
Methods for Planting Moss
There are two effective methods for physically installing moss between flagstones, each suited to different needs and scales. For large or irregular areas, the slurry method is efficient for broad coverage. To create a slurry, blend shredded moss fragments with water and an additive like buttermilk, plain yogurt, or beer. The additive acts as a temporary adhesive, helping the moss fragments stick to the substrate.
The mixture should be a paintable consistency, which is then poured or brushed directly into the prepared joints. A faster method, known as plugging or division, involves pressing small pieces of intact moss mats directly into the substrate. Fragments are pressed firmly into the joints, eliminating air pockets between the moss and the soil. This direct contact with the substrate is essential for the moss’s rhizoids to anchor, leading to a quicker initial establishment than the slurry method.
Long-Term Care for Successful Growth
The first six to twelve weeks following planting are the most crucial for the long-term survival of the moss. During this establishment phase, the planting area must be kept consistently moist to encourage anchoring. This requires frequent, light watering, often once or twice daily depending on the climate, avoiding heavy sprays that could dislodge the newly planted fragments. The goal is to keep the moss damp, not saturated, especially during dry periods, since mosses only grow when fully hydrated.
Foot traffic should be minimized for the first couple of months to allow the moss to firmly adhere to the substrate. Once established, moss is resilient to light traffic, but heavy use will damage the plant structure. Regular maintenance involves gently removing debris, such as fallen leaves, which can smother the moss and block sunlight. Moss is a slow-growing organism that may take a full year or longer to fully knit together into a dense, continuous carpet.