Saxifrage

Sun to part shade — the encrusted silver kinds want sun, the mossy kinds prefer shade from hot afternoon sun.

Low — needs moisture at the root but sharp drainage at the surface; the cushion must never sit wet.

Gritty, lean, very free-draining soil with a gravel top dressing. Most kinds do well on limestone and in tufa or wall crevices.

Snip off spent flower stems at the base and pull out any brown patches in the cushion so fresh growth can close the gap. Nothing else.

Almost nothing: a very dilute feed once after flowering if a container plant looks tired. Fertiliser opens up the cushion and loses the tight form that is the whole point.

Detach individual rosettes with a sliver of stem after flowering and root them in pure grit or a sandy mix. The mossy kinds can simply be divided, since the mat roots as it spreads.

Part shade to full shade — this is the group to use in the difficult dry shade at the foot of a wall.

Medium — tolerates dry shade once established, but establishes much faster if watered in its first year.

Any reasonable soil, including poor and stony ground. Unlike the alpine kinds it does not demand sharp drainage, only that it is not waterlogged.

Remove the flower stems when they finish, and pull out any tired rosettes from the middle of the carpet. That is the whole maintenance.

A compost or leaf mould mulch in spring, and a light general feed only where the soil is exhausted — dry shade at the base of a hedge or wall being the obvious case.

Division could not be simpler: the rosettes root as the carpet spreads, so lift a rooted section at almost any point in the growing season and replant it. This is the standard way to cover a difficult shady strip cheaply.