The cushion saxifrages are ideal dwarf plants for the trough garden, slowly forming tiny domes of green or silverywith extremely pretty on very short stalks in spring. One of the best is S. ‘Jenkinsii’, with masses of shell-pink flowers on red stalks; ‘Valerie Finnis’ is primrose yellow; S. burseriana is pure white and flowers earlier than the others; and there is an infinity of other species and hybrids to appeal to the gardener who is interested in alpines. These saxifrages look well in a trough landscaped with one or two rocks, and could be followed in summer by rock campanulas or Phlox douglasii.
They need a gritty, well-drained, preferably with lime, and do best in light shade, perhaps shielded from the sun by a rock; or the trough could be sited where a building would provide light shade. They also need protection from heavy winter ram, which is anathema to many alpines, and they can be covered in winter with a piece of glass propped up on stones to allow ventilation.
Varieties of Sempervivum. A deservedly popular variety is S.t. Calcareum ‘Commander Hay’, with large crimson rosettes tipped with green, and S. arochnoideum, the cobweb houseleek, has small, bright green rosettes laced with cobwebby white hairs.