Cobbles and pebbles are stones which are smaller than boulders and larger
than gravels (usually in the range 60-250 mm in diameter). As used in garden
design, cobbles are water-washed, by rivers or the sea, and therefore
rounded. Flint and granite form excellent cobble stones. Sea washed cobbles
and river washed pebbles are che choicest. Cheap aggregates are less
desirbale.
Many plants are very happy to grow in cobbles and pebbles. They conserve
moisture and reduce competition from weeds, which also find it more
difficult to germinate beneath cobbles. This arrangement is known to Alpine
gardeners as a scree garden. It keeps the roots moist and the leaves free of
standing water.
Granite