What is actually different about them

A live sheet is a piece of established colony with its structure intact — shoots, accumulated organic matter and developed rhizoids all in place. Laying it is transplanting. The plant is not starting over; it is re-establishing contact with a new surface, which it does comparatively quickly because everything else about it is already working.

A slurry is a suspension of fragments. Each fragment has to regenerate from broken tissue, produce new rhizoids and grip the surface before it can do anything else. That is a slower process with more ways to fail, and it is much more sensitive to whether the surface stays damp during the weeks it takes.

Everything else about the comparison follows from that distinction. Sheets are more expensive because they are more plant, and they establish faster because they are more plant.

Where sheets are the right choice

Flat ground where you want a finished appearance quickly is the clearest case. A shaded area laid with sheets looks like a moss lawn on the day it is laid, and reaches genuine establishment in six to ten weeks with reasonable moisture.

Small high-visibility areas justify the cost easily. A courtyard, the ground beside a door, a Japanese-style planting where the surface is the point — these are places where waiting a season for a slurry to knit is not an attractive proposition.

Sheets are also the safer choice where conditions are marginal. A site that is a little brighter or a little drier than ideal gives an intact colony a much better chance than it gives loose fragments, because the sheet holds its own moisture and shades its own surface.

Laying is straightforward but contact is everything. Firm the surface, clear debris, press each sheet down until it stays put when tugged gently, and butt the edges together rather than leaving gaps. Gaps dry at the edges and are slow to close.

Where slurry is the right choice

Vertical and near-vertical surfaces are slurry territory outright. Sheets will not stay on a wall, a boulder or a steep bank without pinning, while a slurry with a proper adhesive holds well enough to establish.

Irregular surfaces are the same argument. Stone with hollows and ridges, tree bases with exposed roots, statuary, the gaps around set stones — a slurry follows the contour and a sheet bridges it, and a bridged sheet dries out where it is not touching.

Large areas on a limited budget are the third case. A small quantity of donor moss extends a long way as slurry, and where the timescale is a season or two rather than immediate, the economics are decisively better.

Erosion-prone ground favours slurry too, because the mixture binds to the surface as it dries, whereas loose sheets on a shaded bank tend to slide before they grip.

Combining them on one project

The practical approach on most sites is to divide the area by what it needs rather than choosing one method for everything.

Sheets go on the flat ground in the foreground, the part that will be looked at from the house or the path, where an immediate result is worth paying for. Slurry goes on the stone, the tree bases, the bank, the boulders and the ground furthest from view, where a season of establishment costs nothing in practice.

This also has a useful side effect. Established sheets act as a donor source for future slurry work as they thicken, so a project laid this way becomes progressively cheaper to extend.

Where budget is the binding constraint, another approach works well: slurry the whole area, then lay a small number of sheets as anchor patches spaced through it. The sheets provide immediate visual structure and spread outward, while the slurry fills between them.

Aftercare differs more than people expect

Sheets need consistent moisture for roughly six to eight weeks, and misting once daily in dry weather is usually sufficient because the sheet retains water within its own structure.

Slurry needs more attention for longer. Twice daily misting for the first fortnight is not excessive, and the area should not be allowed to dry completely at any point during the first six weeks. Fragments have no reservoir, and a slurry that dries hard before rhizoids form does not recover — it simply blows away.

Both benefit from shade cloth over a hot spell during establishment, and both are set back significantly by heavy watering, which displaces material before it has gripped.

A note on donor material

Both methods depend on the moss you start with being alive and appropriate, and this is where a surprising number of projects fail before they begin.

Moss collected from the wild is a mixed proposition. It is free, it is locally adapted, and in many places collecting it is restricted or prohibited outright, so check before lifting anything. More practically, wild-collected material arrives with soil, weed seed and often a species mix that does not suit the target site, and moss lifted from deep woodland shade rarely thrives in a garden position with more light.

Whatever the source, use it quickly. Both sheets and fragments deteriorate in storage, and material kept sealed in a bag for a week in warm weather arrives as compost rather than as a plant. Keep it cool, keep it loosely covered rather than sealed, and plant within a day or two.

The verdict

Use both. Live sheets establish faster and more reliably, so they are the better choice where you need a finished look and can source or grow the sheets; slurry costs less per square foot and reaches textured stone, walls, and awkward gaps that sheets cannot cover. For most projects the smart approach is sheets on the main visible ground and slurry to paint the edges, joints, and vertical faces — matching each method to the part of the site it suits.

Mistakes people make

The first is choosing slurry purely on price for a small prominent area. The saving on a few square feet is modest and the wait is a season, which is rarely a good trade in the place you look at most.

The second is laying sheets with gaps between them to make the material stretch further. Gaps dry at the edges, the sheet margins brown, and closing them takes longer than the additional material would have cost.

The third is applying slurry to a vertical surface without adhesive. Water and moss alone will not hold on stone, and the application slides off within a day.

The fourth is judging slurry at three weeks against the standard of sheets. Nothing much is visible for the first two to three weeks, and applications are routinely scrubbed off and redone at exactly the point when they were beginning to work.

Frequently asked questions

Sources

1. Oregon State University Extension. Moss in lawns and gardens: biology and establishment. extension.oregonstate.edu
2. Penn State Extension. Moss and algae in turf. extension.psu.edu
3. University of Maryland Extension. Moss in lawns and landscapes. extension.umd.edu
4. University of Minnesota Extension. Drought response and plant establishment. extension.umn.edu