Hardy annuals
Hardy annuals, such as Papaver somniferum and Eschscholzia californica, can be sown directly in position in the garden in spring. Half hardy annuals (Senecio cineraria ‘Silver Dust’, Salvia farinacea ‘Strata’, Tanacetum ptarmaciflorum ‘Silver Feather’) should be raised indoors, hardened off and planted out after danger of frost passed.
Hardy perennials
Hardy perennials (Eryngium giganteum, Lychnis coronaria, Verbascum olympicum) and grasses (Festuca glauca) sown from seed should also be raised indoors and planted out after the danger of frost has passed.
Divide hardy perennials (Achillea, Asphodeline luteus, Cynara cardunculus, Anaphalis margaritacea) and grasses in spring (Helictotrichon sempervirens). Detach and pot up rooted stems (Stachys byzantina, Artemisia ludoviciana). Many can be also propagated by stem tip cuttings from non flowering shoots in early summer (Veronica spicata subsp. incana, border dianthus and Osteopermum jucundum).
Shrubs
Propagate silver leaved shrubs by semi-ripe cuttings from the current year’s growth in mid-summer. Insert cuttings in free draining compost and cover with plastic. Do not overwater and air the cuttings twice a week as they will rot if too wet (Artemisia arborescens, Brachyglotis, Convolvulus cneorum, Helichrysum italicum, Phlomis fruticosa, Perovskia, Santolina chamaecyparissus and Teucrinum fruticans).