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Build a walipini

Want to plant subtropicals and extend the growing season to produce food year round? A sunken greenhouse might be just the spot.

STORY & PHOTOS: CANDY HARRIS

It all started with a picture I saw of an underground greenhouse, a walipini, which was then filed away in the “one day” dream folder. I would never have thought that eight years later, I’d be building my own walipini, making myself one step closer to year-round frost-free growing, plus the dwarf avocado, pineapple and banana I’d dreamed about one day tasting fresh from the source. Talk about stretch goals.

What is a walipini? Walipini means place of warmth in Aymara, an indigenous language of South America. It might also be called a passive greenhouse, sunken greenhouse, or even a pineapple pit; like the name implies, it was somewhere to grow pineapples and exotic fruits in Victorian Britain and other places around the world where temperatures wouldn’t allow for these plants to thrive outside.

The slanted roof angled to catch the day’s warmth via sunlight hitting the back wall (heat sink), along with the soil surrounding the greenhouse, provide natural insulation and warming. Once roofing, windows and doors are sealed in, the walipini also has the ability to prevent frosts. It is also a great option for high-wind areas, preventing wind damage, with the lower external wind catchment.

We had moved to Clarkville, just 10 minutes north of Christchurch, with some land to raise our two boys. I started my ever-growing vegetable garden in a grassy paddock running alongside a spring stream, but the walipini dream was put in the too-hard basket – I didn’t think it was possible here, being close to the stream and not understanding the water table.

So I bought a small polycarbonate greenhouse which we constructed, and I enjoyed greenhouse gardening for a few years, learning what I could and could not grow in the space. Until the polycarbonate panels started cracking and then blowing out in the strong nor-wester winds we get here in north Canterbury, even with me trying to prolong the longevity of the polycarbonate panels by taping and sealing them all in so there were no gaps and movement. The fierce winds and frost won in the end though, and my greenhouse started crumbling before my eyes.

Then the pandemic happened and I started thinking more and more about the walipini. We had the space, we had the time, and we had the willingness to do a lot of the work ourselves. So why not try?

I engaged a local contractor to dig the pit, which went super smoothly and in a few hours, I had my dugout completed. He thought I was creating a swimming pool, like most people who saw it for the first time when I started sharing my journey and photos of the build via my Instagram account, @nzgardener.

Then, it sat for six months while I watched and monitored the drainage over the winter period. I engaged help from a local builder to assist in creating the simple plans and building the framework as this was foreign

Walipini means place of warmth in Aymara, an indigenous language of South America. It might also be called a passive greenhouse, sunken greenhouse, or even a pineapple pit.

to me. I didn’t put any drainage in as the ground is old riverbed and has very good natural drainage. I’ve only had one incidence of flooding (10cm deep) when we had record rainfall and the water table was up for a couple of days. It drained within 24 hours.

The framework took a couple of weeks to complete, with three of us pitching in to get the job done. Another few months of pottering away over the summer of 2020 and 2021 to paint it, get the twin wall polycarbonate roofing panels installed and the whole thing sealed in. The roofing was the most expensive part of the building. To make up for it, I sourced a door for the entrance from the local demolition yard. I thought a nice slim door would do the trick and keep more heat in… well, it barely fits my wheelbarrow – rookie mistake.

The only hiccup was when we hired a digger to help push soil up against the back wall for the thermal mass to warm up during the day. We got it stuck as one of the digger wheels fell between the walipini and the cavity we were filling, it was a frantic couple of hours calling a neighbour to assist with towing it out and removing a panel on the roof so it wasn’t impacted.

I then worked on the external back wall. Some free tyres were stacked three high along the wall and filled with soil. This was to increase the thermal mass that was heated up during the day, slowly releasing the stored warmth as the temperatures dropped at night.

I’ve only had one incidence of flooding (10cm deep) when we had record rainfall and the water table was up for a couple of days. It drained within 24 hours.

Then the fun started: filling it up. I bought some raised garden beds made out of steel. A couple of the beds had to be taller to ensure they got enough light. Filling them all up took many a wheelbarrow trips (lucky it still just fit through the door).

I was determined to use the hugelkultur method so that the beds had nutrients for the next few years as they decomposed below. Little did I know I was creating the perfect environment for rats and mice to overwinter. An abundance of food and warmth, who wouldn’t want to live there, in amongst the decomposing wood, leaves and river weed I’d used to build the beds up? Many, many traps were laid, and pests were caught. It is still a battle to this day (like lots of vegetable gardens are, with rodents). The warmth of the walipini and the smell of fresh passionfruit must call to them from far and wide.

The first thing I planted was my passionfruit vine that had been suffering outside in the Canterbury winter. I’ve never seen a fruit grow as fast as I did that first year watching that passionfruit vine. I’m going to have to give it a hard cut back this year or I might not be able to walk in the door next season.

Then tomatoes, herbs, capsicums, eggplants, luffa, cucumbers, bottle gourds, and I could not forget my dream plants, the pineapple and dwarf avocado. I planted what I thought was a dwarf banana, and by the end of the season, it was knocking on the roof – not so dwarf after all. I had to move it to live outside and then watch it fade away over the winter, though now it’s making a comeback this season. But no bananas yet!

This season, the rockmelons, watermelons and kūmara have thrived in the walipini. I am even attempting a giant carrot which is getting pretty large and almost ready for unearthing. I had early spring zucchini and cucumbers from plants I grew in winter. I also tried – and failed – to grow a strawberry wall using a hanging planter with little pocket planters which dried out way too fast.

The walipini has meant I get a big head start on the season and a late finish. I can get two sowings of cucumber, tomatoes and zucchini a year: when my first plants are looking tired, I’ll resow some more seed for autumn harvests. Melons, capsicums and passionfruit were months earlier than their outside-grown cousins. Leafy greens grow throughout the winter without slowing down: there is food year round. Plus it is a lovely warm spot to hang out when it is cold and rainy outside.

I love a good garden experiment and this was by far my biggest and most successful one to date. I am looking forward to the next one.

CANTERBURY

en-nz

2023-06-01T07:00:00.0000000Z

2023-06-01T07:00:00.0000000Z

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