Autumnal Acanthaceae

Sunday, 28 April 2019

Pachystachys lutea growing in the Royal Botanic Garden Sydney

It's hard to believe that it has been seven years since I launched my little booklet Meet the family Acanthaceae onto the unsuspecting public. A lot has happened in my gardening journey since then, but I am still a huge fan of these easy-to-grow, warm-climate plants. In the intervening years I have trialled a few more members of the family to see how they fare in Sydney. Some are just too cold sensitive to survive our winters, but only the whole, many do very well. I feel I understand the needs of these plants better these days: where once I thought they would all flower well in shade, for example, I now realise that some definitely do better with more sun.

Brillantaisia ulugurica

There are Acanthaceae plants for every season in Sydney and autumn sees a number of these plants in bloom. Some are continuing on from summer (or even earlier!), such as Brillantaisia ulugurica (syn. Brillantaisia subulugurica), with its tall panicles of purple-blue, vaguely orchid-like flowers; Justicia betonica, with its seemingly never-ending upright spires of white-bracted flowers (one which does seem to do better in a sunny spot!); the plump pink or white plumes of Justicia carnea; and the profusion of red trumpets of Ruellia elegans - wonderful, worthwhile plants for colour in our gardens.

Rhinacanthus beesianus

Other begin their blooming period in autumn. One of the most spectacular is Megaskepasma erythrochlamys (ht 2-3 m, often called Brazilian red cloak), a tall shrub with vibrant crimson bracts in bold panicles held above enormous, deeply veined leaves. It will flower in sun or shade, though a sunny spot seems to give the most profuse blooms. Rhinacanthus beesianus (ht 2 m), another large shrub, comes into flower now. In the seven years since I wrote the book, a number of Acanthaceae plants have had name changes, and this is one of them. It was originally identified only as 'Pseuderanthemum species' on its name plaque in the Royal Botanic Garden, Sydney. The new name was identified a few years ago. The plant, whatever its name, is lovely, with clear white flowers shaped liked scalloped shells. The blooms are lightly fragrant. This shrub is another which will tolerate part-shade but flower best with a decent amount of sun.

Strobilanthes cusia

Another pretty Acanthaceae shrub for autumn is Strobilanthes cusia (ht 1.5 m, previously known as Strobilanthes flaccidifolia), which has weeping stems covered in petite pink trumpet flowers. This one will bloom in shady places, in very ordinary soil, and even with root competition from nearby trees. A smaller shrub is Barleria cristata (ht 80 cm), which I have only starting growing in recent years. In autumn it is smothers in simple, five-pedalled flowers in colours of purplish-blue, white or white with lavender stripes. It grows in sun or part-shade.

Ruellia makoyana growing with rhizomatous Begonia cultivars

At groundcover level, cute Ruellia makoyana (ht 30 cm, sometimes known as the trailing velvet plant) has trumpet-shaped, carmine-pink flowers held above silver-variegated foliage. It will grow in dry shade and forms a wide carpet, complementing such shade-loving shrubs as cane begonias, Sasanqua camellias and the many Plectranthus species and cultivars, all blooming brilliantly at the moment.