Salvia or sage comes in an enormous variety of shapes and sizes. Tubular, lipped flower spikes are in pink, red, white, and blue. S. leucantha, Mexican Bush Sages has purple spikes. Being members of the mint family, the foliage is often aromatic. Grow in full or part sun in most soils.
Santolina (Lavender Cotton) is a shrub to around 60cm with feathery, aromatic, silver foliage and yellow button blooms in spring. Light sandy soil and full sun are best. Extra watering over dry periods is beneficial. A good hedge. Frost tender.
Sedum (Stone Crop) is a popular group of succulents. Spikes of starry flowers in flat heads can rise to 60cm but many are very hardy low ground covers. Good in sun to part shade in the rock garden, dry site, hanging basket or container planting.
Selenicereus, the Queen of the Night, is a succulent cacti easily grown in the frost-free garden. Great twining up a post, clinging to a wall or in a basket where the giant white night blooming flowers show to best advantage.
Senecio includes a number of shrubs, groundcovers and climbers with daisy flowers. S. laxifolius is a N.Z. species with silver foliage and large heads of yellow daisies. Dusty Miller is a hardy perennial with silver leaves that can be dried. S. macroglossus is covered with pale yellow daisies and climbs quickly. Provide strong sun, good air flow and keep dryish.
Silene are hardy perennials and annuals good in the rock garden, borders, and gravelly banks. The pretty bladder flowers often in pink and white are related to carnations.
Sisyrinchium (sis-ee-rih'-kee-um) is better known as Blue Eyed Grass. There are yellow and white forms of this tiny perennial with grass-like leaves and delicate flowers that thrive in heat, sun, and sandy light soils or containers. Coastal.
Solanum includes 80 species of Potato Bush and Vine with blue, white, pink or purple star-like flower clusters on hardy, often rampant plants that respond well to pruning.
Sparaxis is a South African bulb with bright, star-like flowers on wiry stems in spring. Excellent is sun or dry light shade and in containers. Plant with ixia and freesia.
Spartium or Spanish Broom has large, fragrant pea-like flowers usually canary yellow or white. Many species are nearly leafless and sprawling but upright shrubs can be created with pruning or grafting. Hardy in poor soils and extreme drought.
Spirea is a North American relative of the rose which in spring is covered with clusters of white flowers. Pink forms also exist. Good in heat, cold, most soils. Hedge or feature.
Stenocarpus, Firewheel Tree, is a spectacular Queensland native for the very warm garden. This 15m tall, slender ever-green is covered in autumn with large, fiery red wheel-like flowers that later mature to resemble medieval crowns.
Strelitzia, the Bird of Paradise, is very drought tolerant but flowers best with ample feeding and a little extra watering around flowering time. Good in the border, on banks and as a large container plant in full or part sun.