Dunedin

Not ev­ery plant can be a tree, stand­ing tall. Some plants' role is to cover the ground and pro­tect the earth.

NZ Gardener - - Contents -

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.

Red alert!

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.

Na­tive bidi-bidi.

Cean­othus.

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