Winter hardy to USDA Zone 10-11 where it is best grown in rich, humusy, medium moisture, well-drained soils in part shade. Plants are tolerant of heat, humidity and some soil dryness. Plants tolerate full sun in cool summer climates. In St. Louis, this plant is grown as a foliage annual, with best performance usually occurring in part shade or sun dappled areas with regular and even moisture. Avoid poorly-drained clay soils. Plants are intolerant of frost. Flower buds may be pinched as they appear when plants are grown for foliage display. 'Silver Shield' may be grown from seed sown indoors about 4-6 weeks prior to last spring frost date. It is easily propagated by cuttings. Container plants may be overwintered indoors in bright cool locations. May be grown as a houseplant.
Plectranthus argentatus, commonly called silver spurflower, is an upright-spreading, woody-based sub-shrub that is native to Australia. Although its flowers are somewhat showy, this plant is usually grown primarily for its attractive, fuzzy, gray-green foliage. 'Silver Shield' is more compact than the species. It typically grows to 24-30" tall and as wide, and features ovate, pointed, scallop-edged, gray green leaves (to 4" long) covered with a silvery sheen. Leaves are covered with down which gives them a velvety texture. Leaves compliment and contrast well with many types of flowering plants. Upright flower spikes (terminal racemes to 12" long) with tubular bluish-white flowers (each to 1/2" long) bloom in late summer.
No serious insect or disease problems. Watch for mealybugs, scale and mites. Root rot and leaf spot may occur.
'Silver Shield' is grown for its attractive foliage. In St. Louis, it is grown as an annual for beds, borders or containers. Good selection for large patio pots. Interesting houseplant.