Plant of the Month: September
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Salvia microphylla
Common name: myrtle salvia
Family: Lamiaceae
Vital statistics
Height and spread: Reaches approximately 1 metre high and wide
Form: Herbaceous perennial
Soil: Light, humus-rich, moist but well drained
Aspect: Full sun
Hardiness: Frost hardy to -10ºC but with some damage |
Making an interesting colour and foliage combination Salvia microphylla can be found on the Dry Garden near Gleditsia triacanthos 'Sunburst' and growing alongside lemon shades of Eschscholzia and Stipa gigantea.
Genus Salvia
Salvia, one of the largest plant genera of about 900 species, is a very diverse genus and includes annual, biennial, herbaceous perennial and shrub species. While two species are native to the British Isles over 500 species can be found in the Americas with the rest being found throughout both temperate and tropical regions worldwide, except in Australasia. They naturally grow in sunny sites including dry meadows, rocky slopes, scrub, light woodland and moist grassland.
All salvias have aromatic foliage, though it is more noticeable in some species than others. The aromatic oils are produced to help prevent the foliage being eaten by animals and help to prevent desiccation in the hot sun where these plants naturally grow.
As with most Lamiaceae the stems of many Salvia species are square in section with the leaves arranged in opposite pairs. The flowers, for which this species is most often grown, are brightly coloured in shades of red, white, blue or yellow with petals that are typically fused into a two-lipped corolla, with the upper lip becoming hooded in some species.
While many Salvia species have become popular in recent years Salvia officinalis, common sage, has been long cultivated as a medicinal and culinary herb. It was probably introduced to Britain in the early Middle Ages, though some believe it was introduced by the Romans. The name Salvia was used by Roman writer Pliny and derived from the Latin salvare, meaning to save or heal.
Salvia microphylla
Salvia microphylla is a native of Central Mexico, New Mexico and Arizona from where is was introduced by G. J. Graham in 1829 to the Royal Horticultural Society's garden at Chiswick. William Robinson, Eleanour Sinclair Rohde and E. A. Bowles all wrote about the plant's beauty, charm and delight about its long flowering period, though it was not until 1880 that it became prized as an ornamental plant.
Salvia microphylla is a woody shrub in its native habitat, but is likely to die back to a woody base if it survives a British winter. It has pale green, ovate, serrate margined leaves which when crushed or rubbed give off a strong odour resembling the smell of black currant leaves. The flowers are bright red in whorls with a hooded upper lip and wide spreading lower lip and will bloom from July to November, or later if it is not caught by the frost. It is hardy to -10ºC but not without some damage.
AGM
The RHS has awarded several cultivars of Salvia microphylla with Awards of Garden Merit.
Cultivation
Salvia microphylla can be grown outside in a sheltered, sunny location and will survive several degrees of frost. However, in all but the mildest parts of Great Britain it is advisable to take cuttings during the summer and over winter plants under cover in case the border plant fails.
Pruning can be kept to a minimum though if left unpruned Salvia microphylla will become leggy and lose its compact habit. Tip prune shoots to encourage branching and once established cut back to a framework of woody stem in spring, after the last frost.
Slugs and snails will attack young, soft growth throughout spring and summer while aphids and whitefly can infest plants outside during the summer or at any time under glass.
Propagation
Salvia microphylla can be raised easily from seed but it hybridises readily with S. greggii so should be propagated by cuttings to raise plants true to S. microphylla.
Salvia microphylla can easily be propagated by softwood cuttings in spring or semi-ripe cuttings during summer and autumn.