Build a Hotbox for Cool-Weather Gardening

Reader Contribution by Jenni Blackmore
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Who says inanimate objects can’t talk! The well-used tractor tire that washed up on the beach during an early winter storm had been pleading with me for months for a chance to prove its worth.

“New house rules”, I explained. “Not allowed to introduce any new-found treasures to my already sizeable cache without a solid repurposing plan, accompanied by a realistic timeline.”

“No problemmo!” the tire was quick to reply. “Allow me to introduce myself. The best, easy-peasey, earliest-ever spring greens hotbox. At your service!”

And with that, it rolled itself blithely up the path from the beach, over the tailgate and into my truck.

First Things First

Back at QuackaDoodle Farm, the tire was set up on some previously uncultivated ground which was rife with weed growth and definitely in need of an initial mulching with sheets of cardboard.

Eventually it will be incorporated into one of the food forest guilds I’m developing in this area and it already has a certain amount of protection from the fiercest of the winds we experience on this little island.

The Stinky Part

The next part of the earliest-ever spring greens plan required a shovelling out of the chicken shed. Not quite so easy-peasey, but fresh chicken manure is the heat source for the hotbox, so I did what needed to be done.

Packing the fresh manure into the cavity of the tire spoke volumes to my inner child as it was reminiscent of those blithe sand-box days, only much smellier. I found claw and trowel hand tools, used much like salad servers, along with a long-handled claw rake worked best for this. And, of course, a good pair of rubber gloves.

Burn Prevention

The next step, after the tire cavity was packed with manure, was to line the inner circle with plastic, creating a barrier which will keep the manure in place, but also, and more importantly, will prevent it from coming in contact with and burning the roots of the young greens.

While fresh chicken manure is way too potent for direct application, the heat it generates will help heat up the soil in the inner circle of the tire. The black rubber composition of the tire will also contribute to this heating process.

With the plastic barrier in place I spread a layer of manure over the cardboard in the inner circle and topped this with a generous layer of leaves to create a buffer zone. This will enable the plants above to benefit from the heat of the manure while not having any direct contact with it.

Adding the Soil and Seed

The hotbox was then finished off with several inches of a rich soil mix and planted with various early salad greens including Mesclun mix, Tat Soi, Arugula and Oak Leaf lettuce.

It was finally tucked in under a couple of layers of semi-transparent plastic, which I weighted down with an outer dressing of straw and eel grass. While not essential, I believe this outer organic mulch will help keep the heat in, especially if we get more snow, which we no doubt will.  Low temperatures are presently hovering in the -1 to -10 range, but there’s rumours of an “Artic vortex” heading our way.

Now, I’m not sure exactly what that is, but I just know it doesn’t sound too warm and fuzzy. If things get abnormally cold — and what is normal anymore when it comes to weather patterns? — I can always pile straw on top of the plastic cover as an extra protection for the tender seedlings.

Whys and Wherefores

I’m sure anyone living in more benign weather zones might well be wondering, but why go to all that trouble? Those living on the east coast of Nova Scotia and any place with a similarly late arriving and often short-lived growing season will understand why all too well.

I have used the hotbox system in a typical cold frame to extend my late season crop and found it worked really well. It’s actually a traditional method that was used extensively by les maraîchèrs or market gardeners who kept Paris in fresh veggies during the eighteenth century.

I first learnt about it from Elliot Coleman in his Winter Harvest Handbook, but long before that the Russian anarchist writer Prince Peter Kropotkin had described the process in 1899.

How my noble little tractor tire knew all this I can’t imagine, but I do believe that having “the walls” of the box emitting heat as well as the floor should make the system even more effective.

After I’ve harvested the greens, I’m going to replant the tire with a couple of the sweet potato slips that are presently thriving on my kitchen window sill. This will be really stretching the limits of what we can grow around here and I might not have considered growing them except for a certain sweet potato that insisted that she wasn’t intended for the table and underlined her argument by sprouting profusely.

A Permaculture Perspective

In terms of permaculture, I’m loving this project as I’m able to reuse, in this case some ugly flotsam (sorry tire, but you just didn’t look that pretty half buried in the sand), venetian blind slats cut into markers for seed placement, and some heavy-duty poly that had previously protected a pile of firewood.

I’m maximizing on location by creating a micro-climate and by taking the first steps towards establishing another guild in the food forest, while also reclaiming ground that had been devastated by a hurricane. Also, I planted the seeds in a spiral formation to honour the design inherent to natural growth patterns.

Perhaps best of all, this hotbox has not cost me a cent so far, and after a couple of years, the manure and the leaves in the tire will have blended themselves into a trove of super soil. Definitely a win/win/win in my book.

Jenni Blackmore’s passions are grounded in the nitty-gritty everyday of permaculture and micro-farming. Jenni calls her place QuackaDoodle Farm for obvious reasons, even though the goats and rabbits complain they’re not getting fair billing. Her book,Permaculture For the Rest of Us,recently publishedbyNew Society Publishers,has allowed her new ways to spread the word about permaculture. Connect with Jenni onher website, her farm site, andFacebook.

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