Not every plant can be a tree, standing tall. Some plants' role is to cover the ground and protect the earth.
Margaret Barker’s amazing purple and red groundcovers.
They provide a haven for little critters and the microorganisms in the soil. We gardeners call them groundcovers and choose those that are decorative to create a layered garden picture as well as enhance the precious life of the soil. Two stalwart green groundcovers are Scleranthus biflorus and Azorella trifurcata.
Scleranthus, native to New Zealand and Australia, forms a bright green, fine-textured mat.
It thrives in poor soil or gravel in sunshine. Too much shade or rich soil and it will lose its tight texture and die out in the middle. Prostrate at first, it eventually forms interesting mounds. I once saw this in a stunning, but now lost, Christchurch garden designed in the Japanese style with scleranthus used instead of moss. It was punctuated by cycads, dwarf weeping maples, evergreen azaleas and bamboo.
The azorella comes from South America, from Argentina south to the Falkland Islands.
I have seen it growing wild in the Andes surviving on just rocks and gravel. Three pointed leaves form rosettes of lustrous dark green, a nobbled carpet which contrasts with the lighter matte green texture of the scleranthus.
Both of these plants can be lifted and divided into rooted pieces and spread to form extensive carpets. Both also grow easily enough from cuttings. In the garden at Larnach Castle, the scleranthus seeds into gravel and light soil.
Ceanothus are native to California but we can claim the cultivar ‘Blue Sapphire’ which was bred in New Zealand.
In November, sparkling sapphire blue flowers smother this low-growing shrub. The fine-leafed foliage on arching branches turns almost ebony in winter – a fashion statement in black. It would be worth growing for its dramatic foliage alone. This plant can be pruned for shape or containment just after flowering.
I grow it as a groundcover but I’ve seen a photograph of it planted in a narrow bed at the base of a wall. It grew upwards to clothe the wall. I don’t know how much training was involved to produce this stunning effect. Plant ceanothus in sun in light, well-drained soil.
Ceanothus, like members of the pea and broom family, are pioneer plants for nutrient deficient soils. The plants have nitrogen-fixing nodules formed by bacteria on their roots which take nitrogen from the air to feed the plants. When the plants die, the nitrogen is returned to the soil, increasing its fertility.
New Zealand’s red bidi-bidi,
Acaena inermis ‘Purpurea’, is a pestilential presence in the Larnach Castle South Seas Garden. Information from here and there suggests its spread as 1m. What a fib. This plant has rolled in waves far and wide across and interweaving with its neighbouring plants, in some cases depriving them of light and killing them. Some sources say to feed it. Don’t bother. It does all too well without any attention.
If you must, plant it in sun for its rich colouration but keep your eye on it and contain its spread on a very regular basis. This plant is most prevalent in the wild on the eastern side of the South Island. Perhaps that is why it has made itself so at home here.
Unlike most bidi-bidis, it doesn’t have barbs or spines on its seedheads, so it doesn’t stick to your socks.
To my mind though, that does not make up for its predatory habits.
Ceanothus sits between azorella (foreground) and scleranthus.