- Bedding down an undercover jungle is no child's play.

Yes, winter is here, and it gets extremely chilly in Southland, but these plants don’t need to know that.

It was time to prepare for cold weather and ensure the survival of the subtropical plants I’d enthusiastically collected and planted over the summer. My holiday in Golden Bay had yielded a wonderfully exotic collection of frost sensitive plants: bananas, gingers, pawpaw, carob and many other shouldn’t-be-in-Southland beauties and they needed swaddling against the cold.

I began with the bigger bananas, wrapping their thick stems with scraps of coconut fibre mat (leftover from some project), then draped the smaller plants with white lace curtains, bought secondhand where possible, creating a scene akin to something from a Pacific island wedding.

It’s definitely worth going to the trouble of covering up and not just hoping those sorts of plants will be tough enough to navigate the winter conditions without suffering frost damage or death-by-chilling. I’ve tried that many times before and my appalling record with lemon trees in the open garden is testimony to the need to take precautions.

I’ve covered the young, soft-leaved brugmansia with plastic water cooler bottles with the bottoms cut out.

I’ve also stacked old roofing slates around the base of some plants, in the expectation that the heat they gather – they’re dark grey – will then radiate through the chilly night.

The most fun I’m having in the tunnelhouse though is not the frost protection but the soil enrichment.

The vibe I’m going for with my plantings is jungle: large, glistening, arrowhead-shaped leaves, opulent flowers, twining vines and luscious fruits, but they’d all look wrong growing in bare soil.

My imaginary jungle – I’ve never been in a real one – is ankle-deep in fallen bracts, spent flowers, shed tendrils, the discarded skins of brightly coloured fruits, flung-aside husks, gnawed-upon nuts, the sloughed skin of reptiles, discarded butterfly wings and the spent carapaces of strange beetles. So I’ve been busy creating something like that, using materials from my garden and beyond. It’s looking pretty convincing, I think, though the layers of seaweed would make anyone who’s seen a real jungle-floor, scratch their head. The avocado skins and stones, walnut shells and coffee grounds look in-theme if you don’t think about it too much, and the horse manure, while clearly not from a jungle animal, could pass as tapir poop or ape droppings, if viewed through a creative eye (or nose).

I’ve decide to enrich the soil in the tunnelhouse with everything I can gather from wherever I go, and I’m in the kitchen a lot. I’ve trained myself not to waste anything that might add to the richness of my jungle floor. All of my coffee grounds and any left-in-the-cup liquids go out there, along with carrot peelings, beetroot tops, banana skins and so on. I add the pulp left over from a day’s work on the cider press; buckets of heritage apple skins, stems and pips, and windfalls from the fruit trees, collected into a wheelbarrow and pushed uphill to the tunnelhouse; mushrooms picked but not processed in time, go in with the mix, along with the leaves scooped from the house’s spoutings; spent potting mix from nursery experiments – anything really, that approximates the tropical outdoor carpet.

It’s working and looks, well, like a compost heap, but by springtime, it’ll be just what I imagined. I’ve cut leaves from the biggest banana, the tamarillo that’s pushing up the plastic on the roof of the tunnelhouse, the towering cannas and the too-vigorous zantedeschias and laid those out artistically, to add to the exotic impression.

My most recent innovation is two worm farms, made – without frames or containment of any sort – by piling up wet leaves, the beech and birch from the spoutings, in mounds and introducing tiger worms. I hope they will stay under their leafy blanket, feeding, until their numbers have grown sufficiently that some of them can migrate into the jungle floor proper and turn that into worm cast.

If that happens as planned, I’ll be able to keep supplying the space beneath my plants endlessly.

If the frost or cold night temperatures do cause some of my subtropicals to expire, they too can join the party on the floor and become soil that will help their surviving mates to grow stronger here in their southern mini-jungle.

I’ll be disappointed to lose anything that does succumb, but at least they’ll look good in their final resting place.

The seemingly endless, best-ever Southland autumn finally began to wind down and the unseasonably high temperatures, drop. ROBERT GUYTON grows everything that’s willing to make the effort in his food forest garden in Riverton on the south coast of the South Island.