Colloquially this plant was known quite erroneously as 'giant salvia' when it became available in some nurseries in recent times. It is an incredibly long-flowering warm-climate shrub which does very well in Sydney gardens. Rather than being a Salvia, it is a member of the broad Acanthaceae family and originally comes from tropical Africa. In bloom from late spring until the end of autumn, it has dramatic panicles of large, vaguely orchid-shaped flowers, each with a speckled, claw-like, pale lilac upper petal above a large purple-blue lower lip. It has huge, lush leaves, and fleshy square-sided stems which can grow up to 3m tall.
It does best in a sunny position with reasonable soil, but will also grow and flower quite well in light shade. It is an ideal companion for tall Salvia, Canna, Hibiscus and Tibouchina, and its flower colour mixes easily with almost any other hue. It is best sited at the back of flower borders, where surrounding shrubs can support its tall stems. It may benefit from staking, as the plants become top heavy after rain. Take off the spent flower-spikes, and new ones will form. It can be cut almost to the ground in late winter and then will regrow very quickly. It takes root very easily from cuttings during the warmer months.
The Acanthaceae family to which it belongs includes many plants which thrive in our gardens, such as the oyster plant (Acanthus mollis) and forest bell bush (Mackaya bella) which flower in late spring; jacobinia (Justicia carnea) which flowers in summer and autumn; and winter-flowering goldfussia (Strobilanthes anisophylla), firefly (Justicia rizzinii) and Christmas pride (Ruellia macrantha). Some, such as Persian shield (Strobilanthes dyeriana) and polka-dot plant (Hypoestes phyllostachya), are grown for their decorative foliage. Another relative is the so-called red justicia (Odontonema tubaeforme), which has bright red glossy spikes of flower in late summer and autumn. Most members of the Acanthaceae family are sensitive to hard frosts, but if grown under a tree canopy they should be well protected. All these plants cope very well with hot summers in Sydney.
Most of these strike very readily from cuttings and in general they are excellent plants for shady areas in the garden where it is sometimes hard to establish flowering plants. They have long been stalwarts of Sydney gardens, so Brillantaisia is joining a very useful group of plants.
Note:This plant has been previously referred to by me as Brillantaisia subulugurica, which is now identified as a synonym of the correct name.