RE: Oyster Plant - a highly regarded plant in Ancient Rome and Greece.

Acanthus Mollis
A horticultural survivor from Ancient Greek and Roman times, Acanthus mollis is one of the great garden plants. It was so highly regarded in the ancient world that a motif shaped like an acanthus leaf was used to decorate the tops of Corinthian columns.

Acanthus mollis is the old-fashioned oyster plant. From a wide clump of large, glossy, jagged-edged leaves, arise spires to a height of a metre or more, of white flowers delicately veined with purple and held within purplish-brown shell-like bracts. It is in bloom from late spring to early summer. Its foliage forms an attractive groundcover below trees or between shrubs. The leaves sometimes disappear for a time after flowering but soon return and they are particularly luxuriant in winter. A member of the broader Acanthaceae plant family, most of which grow very well in Sydney, it shares with its relatives an ease of cultivation; an ability to grow in shady places; lush and attractive leaves; and decorative two-lipped flowers, often surrounded by distinctive bracts.
The oyster plant looks its best in shade or semi-shade. It needs reasonable moisture, and protection from snails. Otherwise, it is an undemanding plant. However, it is very hard to eradicate if you ever decide to get rid of it, as the tiniest piece of root left behind will become a whole new plant. It is also a keen self-seeder, so its flower spikes should be removed and destroyed (not composted) before they set seed. The huge leaves can at times swamp nearby plants - one idea is to remove some of the leaves at the base. it doesn't seem to affect the vigour of the plant.

The distinctive dark/light tonal colour scheme of its flower spires suggests some interesting possibilities for companion plants. A nearby substantial shrub with purplish-brown leaves - such as one of the Japanese barberries (e.g. Berberis thunbergii f. atropurpurea, ht 1.5m) - could mirror the hue of the acanthus's flower bracts. The contrasting whiteness of the flowers of the oyster plant can be echoed by other white flowers in bloom at the same time in shady spots, such as frothy renga-renga lilies (Arthropodium cirratum, ht 60cm). Some of the oyster plant's own relatives also provide suitable companions for it: one that flowers at the same time is the forest bell bush (Mackaya bella, ht 1.5-2.5m) with pale lilac-white, bell-like flowers, finely etched with purple, the same shape as those of the oyster plant. Shrubby winter-flowering goldfussia (Strobilanthes anisophyllus, ht 1.5m) has slim, dark purple-suffused leaves which echo the dark bracts of the oyster plant's flowers.