"Meet the Acanthus family"

I have recently discovered this congenial group of flowering plants, which has some excellent shade-loving specimens.
Sunday, 24 May 2009     

Strobilanthes flaccidifolius

For the sunny borders in my garden, Salvia are my great plant obsession, but in recent times I have discovered another congenial group of flowering plants which contains some excellent shrubby perennials happy to strut their stuff in shady places in our Sydney climate. The Acanthus family (Acanthaceae) is a significant group of tropical ornamentals, many of which hail from moist forests. They are all easy to grow. Most are frost tender, but because of their preference for shade they usually will have the protection of overhanging trees or shrubs. They flourish in reasonable soil with sufficient moisture and occasional mulching, but they will accept more ordinary situations with equanimity.

Family characteristics include flowers which are usually two-lipped, with four to five petals, one or more of which may be formed in the shape of a protruding tongue. The flowers may be solitary (usually in a funnel, bell or tubular shape) or held in spikes, and often have colourful bracts. On the whole, they flower over a long period. Their leaves are usually soft and lush. In some cases, the foliage is highly decorative.

Many of them are old-fashioned plants which have been around for years. They were the sort of thing grown by your grandmother down near the chook-pen, or sold in a rusty tin-can at the school fete, and never really given a second thought, because they grew and survived so easily. Others are more rare, but are still easy to grow.

They obligingly arrange amongst themselves to flower in different seasons to give a variety of interest through the year. During the last few months, the autumn-blooming ones have been decorating the garden, and many of the summer-flowering ones (such as Justicia carnea, Justicia brandegeeana, Dicliptera sericea and Brillantaisia subulugarica) have, as usual, continued their display until the really cold weather set in a few weeks ago.

Autumn favourites include the shrubby red justicia (Odontonema strictum, ht 2m), with plumes of blood red, glossy flowers from late summer until the end of autumn. Its large, lush leaves provide a good foliage background for the rest of the year. Orange-scarlet tubular flowers belong to Ruellia graecizans, a smaller shrub to about 60cm. The flowers have a neon quality, which makes them stand out brilliantly in shady areas. It does tend to self-seed a bit. Another proliferous specimen is the so-called ribbon bush (Hypoestes aristata, ht 1.2m), shown a few paragraphs above, which is smothered in curling bows of small mauve flowers in May. It is one of those very common plants which, however, can look very effective if looked after properly. It makes a pretty companion to Camellia sasanqua, complementing the pinks and whites of their blooms.

Another good subject to grow near to Camellia sasanqua is Justicia brasiliana (previously known as Dianthera nodosa), a small shrub about 50cm tall with pretty pink fans of flowers in late summer and autumn. This one also associates well with the shrubby Plectranthus of autumn, as does Ruellia makayona, an attractive groundcover from the Acanthus family, with silver-veined, dark-backed foliage and gorgeous carmine-pink funnels of bloom in autumn.

Another shrubby specimen I like is the Chinese rain bell (Strobilanthes flaccidifolius), shown at the start of the blog, which starts to bloom around May. A relative of the familiar goldfussia (Strobilanthes anisophyllus), it has lush, glossy foliage and pendulous sprays of dainty pink trumpet-like flowers - it resembles a sort of fountain when in full bloom. It thrives even in quite dry shade: I have one of mine growing right next to a huge conifer.

My most recent Acanthaceae acquisition is a Rhinacanthus beesianus. It is quite a tall, shrubby plant to about 2m, and around April starts to produces clusters of brilliant white, shell-shaped flowers which are sweetly perfumed. Its big veined leaves are a useful backdrop to other plants.

All of these plants need to be cut back ruthlessly in late winter - around mid-August. Left unpruned, they will all become hideously straggly and bring discredit on their family name. A handful of fertiliser applied after pruning will help them to recover from their haircut.

The Royal Botanic Gardens in Sydney has many of these plants growing in its borders and plants can be bought from the Growing Friends' Nursery there, which is open from Monday to Friday from 11.30 am to 2 pm.

Please let me know if you have enjoyed growing any of these plants: tell me I am not alone in my love for Acanthaceae!

 Reader Comments

1/4  Jan - 2072 (Zone:10 - Warm Temperate) Monday, 25 May 2009

Hi Deidre, Always enjoy your blog so please keep it coming. May I ask you if Acanthus Mollis is from the same family of which you are speaking. Cheers Jan

Hi Jan, thanks for your comment. Yes, Acanthus mollis is in this same family - see my past blog 'Acanthus and Kin'. Regards, Deirdre

2/4  Margaret - 2122 (Zone:10 - Warm Temperate) Saturday, 30 May 2009

Hi Deirdre, like the others, I love your blog - it is always most informative and well presented. Looked the other day at the RBG re Pseuderanthemum and the blurb only says it was collected in China. Margaret

Thanks, Margaret. I hope one day we will find out what species your Pseuderanthemum is! It is proving to be a great plant. Deirdre

3/4  Belinda - 2048 (Zone:10 - Warm Temperate) Monday, 27 May 2019

Hi Deirdre, I"m currently studying Landscape Design at Ryde TAFE and we are looking at Tropical Plants at the moment. There"s a whole new world out there. The timing for your Blog is perfect particularly with the ACANTHACEAE family. I"m only new to your website but really enjoying it!! Thank you, Belinda Hi Belinda, that is great that this blog is relevant to your studies. These plants are certainly well suited to our Sydney climate. Good luck with your course. Deirdre

4/4  Beth - 2257 (Zone:10 - Warm Temperate) Monday, 27 May 2019

Yes! I totally agree with you, Deidre. I have grown Justicia (Odontonema strictum) for over 20 years and it is a trooper. My husband occassionally hacks it back but it only serves to encourage a better looking plant. Honestly, I think it would grow on cement! I have plants self seeded in between large rocks on a retaining wall. They are never watered or fertilized and our soil is infertile sand but they thrive nevertheless especially those in filtered sun. I must keep an eye out for its cousins! It is such a tough plant! I have made a hedge out of it in a shaded area and it is a real trooper. Deirdre

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