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Roundwood Roof Beams

How I’m building the roof for my new passive solar greenhouse.

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Instead of having a ugly parking lot, we decided to build a kitchen garden close to the house so we could quickly gather ingredients for meals.

First Steps

We needed to cut some trees to ensure enough sunlight would reach the garden throughout the seasons. We used the firs and hemlock for firewood, and the cedars for fence posts. We burned all the branches to make a large quantity of relatively high quality biochar. Biochar sells for prohibitively high prices, so being able to create our own is extremely valuable.

Quite a lot of trees to process by hand!

Once the trees were felled, the biochar made and the logs stacked, work could begin on converting the compacted parking lot into a productive garden.

The parking lot before construction began.

But how to turn compacted sandy dirt into productive and biologically active soil?

A diverse blend of cover crops would work well as their roots could punctuate the tough dirt and start pumping carbon into the ground. But this would require at least a year (and with the level of degradation and compaction here probably more like 3-5 years) to become ready for planting.

The Solution: Hugelkultur

We opted instead to dig trenches 2 feet deep, 4 feet wide and about 24 feet long. We would then fill these trenches with hundreds of pounds of old stumps, logs and rotted woody debris, then cover them with organic matter (grass, manure, compost, soil, etc) and plant directly into the top.

Seb began digging by hand but quickly realized this would take ages and the opportunity cost was too high so we hired our friend Larry to come with his machine. Larry, an old-school organic farmer (well before organic was popular) was somewhat skeptical, but got the work done within a day.

Larry getting to work!

Once the trenches were dug and filled with the material it looked as if no work had even been done. But hiding under the tire tracks and dirt was thousands of strands of hyphae getting ready to colonize the vast amounts of woody material. Around this time Seb dug in new water lines so sprinklers and hoses could be run.

The Benefits of Hugelkultur

The woody material is covered by organic material and soil so it begins to collect water like a sponge. This reduces your watering needs considerably. Once the plant roots are established you almost never need to water because the wood becomes saturated.

The constant moist conditions also allow fungi to rapidly colonize the abundant woody food source. Fungal decomposition builds high quality soil, so the hugelkultur beds actually improve their soil quality every year for about 5-7 years with no added inputs or effort on your part at all.

Lots of wood also fosters mycorrhizal associations between certain fungi and plant roots. This fungal connection helps the plant roots collect nutrients and minerals from a far bigger area than would be possible with their roots alone. Through root educates the plants can also request specific nutrients or minerals at specific times. This is a much more fine-tuned nutrient application than even the most high precision conventional (or even certified organic) agriculture can achieve. In short, increasing the fungal component in soils in beneficial for many types of crops.

  1. Better water retention
  2. Promotes beneficial fungus
  3. Builds soil without any effort (once it’s built)
  4. Is significantly cheaper than buying soil or compost

Planting the beds

Once the trenches were filled with wood we piled on grass clippings, horse manure (we bought this from an organic farm near us, but we are aiming to stop all external inputs in the near future), homemade compost and forest soil. This created a fantastic planting medium that was biologically active (from the compost) and contained tons of organic matter for that life to feed on.

Planting begins. These tiny plants were started inside from seed.

Starting a kitchen garden with no fence is a risky proposition so building a fence became high priority. Seb began stripping the cedar logs, and learning to dig post holes. Most of the post holes were dug 2 feet deep. He also built a garden shed as a way to learn the skills needed to build his passive solar greenhouse (not completed yet).

A simple garden gate

With the plants in the ground, water lines dug, the fence built and copious amounts of straw mulch (inoculated with King Stropharia Wine Cap edible mushrooms) applied, the garden was ready to go.

2022 Results

This kitchen garden produced a large amount of food for us this season and was overall a much higher success than we were expecting. We picked about a half pound of perennial kale daily for 2 months at least. Carrots, beets, runner and bush beans, fennel, amaranth, swiss chard, sunflowers, dill, basil, thai basil, strawberries, chili peppers, leeks and more all prospered and suffered no nutrient deficiencies. Volunteer butternut squash produced around 45lbs. We planted asparagus and strawberries together and hopefully in 3-5 years the asparagus will produce a nice early spring vegetable. Pests were not a problem at all because the population of beneficial insects loved the spaces in the mulch and were able to increase their numbers greatly.

Next Steps

A passive solar greenhouse will be built on the south side of the garden. This will be used to start seeds, grow tomatoes, peppers and other hot season crops and maybe even to extend our growing season year round.

The paths will be planted with low growing white clover as a living mulch. Clover is a nitrogen fixer so it will provide the adjacent garden beds with nitrogen.

A large variety and number of flowers will be seeded all around the garden to increase pollinator populations, and to attract even more beneficial insects.

The fences will be planted to runner beans, and maybe grapes or some other vine/espaliered tree to take advantage of the nitrogen from the beans.

Before and After

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DIY

Building a Garden Shed

Using cedar posts harvested 30 feet away, this shed was built in 4 days for less than $340CAD.

This was built so that Seb could learn the skills required for the next project: a passive solar greenhouse using cob or wattle and daub. Everything in this build free except for some hardware and the plastic roof panels.

    March 16, 2022

    Using packed earth tires as a thermal mass, this simple coldframe extends our season by 1-2 months in the spring and fall.

Simple DIY

Passive Solar Coldframe

Using packed earth tires as a thermal mass, this simple coldframe extends our season by 1-2 months in the spring and fall.

What is a coldframe?

A coldframe is essentially just a mini greenhouse. It protects plants from cold temperatures and can help growers in northern climates increase the length of their season.

Thermal Mass Wall

This design adds a passive solar element. By having a large, heavy wall (on the north side) made of tires filled with dirt, we are capturing sunlight and heating the tires. At night this heats is radiated back into the growing space keeping the plants warm.

The build

This was a very simple (and not very elegant) build. We used all recycled materials (even the hinges), and so it only cost a couple dollars for screws.

Planting

We decided to make a mini hugelkultur bed because we were low on compost and soil. We laid down a few logs in a trench and then covered them with leaves, sticks and some unfinished compost.

As an experiment to see how lazy we could be, we didn’t add any finished compost or soil and just threw seeds directly on top of these leaves and unfinished compost.

You can see kale seeds strewn randomly in this rough unfinished compost.

It seemed like this couldn’t possibly work because we weren’t even planting into soil. But the plants sprouted and took root, their roots snaking down to the moist and rapidly decomposing logs below. We had fresh salads and baby greens by the end of April, barely after the snow had melted. Overall this was a massive success. The lessons from this coldframe will be applied to our full size passive solar greenhouse.

Results

In the spring nighttime temperatures would routinely reach -5C, but the coldframe never had a killing frost, and didn’t even appear to freeze at all. The cold hardy plants (kale, mustard, lettuce, swiss chard) all established themselves from seed and grew well. This cold frame allowed us to significantly extend our growing season and have fresh greens earlier.

Update 2024. We decided to dismantle this and focus our efforts on consolidating our garden space, but this was a cool experiment showing the power of thermal masses collecting and reflecting heat into a space.

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Check out some other stuff we’ve been working on.

    May 23, 2022

    We generate a lot of woody biomass from branches which we burn in pits to make charcoal. We then inoculate this charcoal to make a soil amendment that can last for over 1000 years in our soil.