This shrubby salvia is reported to be a cultivar of Salvia splendens and is a very valuable plant, which flowers almost all year in a warm temperate climate. It is said to be an early Dutch selection that was made of Salvia splendens before the dwarf forms were bred for popular bedding plants. The plant was named for Louis Benoit Van Houtte, a keen nurseryman sometimes called 'the father of Belgian horticulture'. It has relatively large, tubular maroon flowers, held in a dark calyx. The plant grows to about 1 m tall and as wide, and prefers to grow in part-shade, especially in hotter areas. Sometimes it self-seeds, giving rise to slight variations in colour. It is quite frost sensitive; in colder areas prone to frost it would be best grown with overhead shelter from tall trees. In cold areas, it is regarded as a perennial but in mild regions it develops a woody base like a shrub. As it flowers almost continuously (seeming to have a rest in mid-summer in my garden), it can be pruned progressively, by removing one woody stem on a regular basis through the year. Alternatively, it can be hard-pruned along with most of the shrubby salvias in late winter: it will quickly regrow. It looks particularly effective with blue flowers, such as Agapanthus cultivars, annual browallia (Browallia americana) and perennial asters; silver or plum foliage also combine well with the hue of its blooms. It can be grown in a large pot. It can get quite woody after a few years - replace with a cutting occasionally.
I once had a form of this plant with a scattering of yellow spots on its leaves. It grows quite well in shade and can look effective grown nearby yellow Abutilon or yellow-flowered bromeliads. There is also a variant named 'Alan's Maroon' with more clustered flowers of a more intense and vibrant colour, which is always in bloom.