Design notes…

Finished: a new garden

Measuring flexible piping to make the netting support. A length of flexible soaker hose has been laid and remains in the garden. The citrus and associated plants in the tub at left are netted to exclude possums and pademelons that especially like the chives growing around the citrus. The blue tarp kills off weedy grasses to prepare the area for the next garden bed.

WITH THE DEPARTURE of winter’s rains our soils start to dry and it comes time to think of garden construction. Soils around here reach field capacity in winter.

Now, our first bed is built and the seedlings we planted are feeding us.

Making the garden

To make the beds we reused the wooden plank railings from the balcony, now replaced with stainless steel wire. Using an electric driver to save time and effort, we screwed the planks to short star pickets driven into the ground.

Fiona is a woman with an engineering-type mind, so it was no surprise that she made much use of measuring tape and bubble level to constantly check that the angles were right and the edges were equidistant and level.

‘Wait’. That was Fiona. ‘This edge is three centimetres out. We’ll have to pull it apart and rebuild it.” So we did. She thinks my aligning-it-by-eye approach is, to use her term, ‘slapdash’.

The blue tarp spread over the ground in the photo is our attempt at genocide of the prolific capeweed. I have since started to cut and fill an additional garden bed there.

Garden mulched and soaker hose laid, all but one of the netting supports has been installed.

Using permaculture thinking

We made use of the two types of permaculture thinking — design thinking and engineering thinking.

Design thinking—the planning phase

We began with the site analysis that is the starting point of design thinking and that discloses site opportunities and constraints; these included:

  • an assessment of seasonal winds (strong and cold winter winds from the south-to-west sector)
  • seasonal rainfall, most of it in winter and sometimes lacking in the warmer month, leading to dry soils
  • slope (steep)
  • drainage
  • soil characteristics (sandy with some loam)
  • diurnal sunlight/shadow movement across the site through the year
  • what is already growing and what, is anything, it indicates about the site (the capeweed indicates wet soils)
  • wildlife—it’s a bit of a nocturnal zoo here with the a mob of pademelons, possums, bandicoots digging holes, and during the day the occasional echidna and blue tongue lizard along with hundreds or yellow-tailed black cockatoos; ravens; magpies; the occasional green rozella and lorikeets, kelp/pacific/silver gulls; herons; kookaburras; mynahs; butcher birds; a couple sea eagles that glide by; a wedgetail eagle recently sighted, high-velocity starlings; noisy plovers and other avifauna that drifts by.

Access a consideration

We considered access, thus the 360mm wide, barkchip-filled access path running the upslope length of the garden bed, and what will be a wider, wheelbarrow-accessible path on the downslope side. Between the upper edge of the top path and the fence, a narrow strip will grow perennial and annual flowering plants to attract pollinators.

The bed, and others to follow, is used to grow annual vegetables so it located close to the kitchen for convenient access and monitoring.

Identifying site constraints

The garden bed and another now in construction are located upslope and adjacent to the fence. Future garden beds will be built between a couple wastewater infiltration trenches — there is no mains water or drainage connection in our town. Rectangular garden beds are thus the optimum shape. Rectangular beds are more-easily-maintained than curving garden bed edges.

With no mains water supply, and living on the drier southern coast of the state, we rely on rainfall for irrigation. Other than directly rainfed, irrigation comes from the same source as the house supply—runoff from the roof stored in rainwater tanks. That makes water-conserving irrigation a necessity.

Site opportunities and constraints determine optimal design.

Almost finished. Composted and mulched with only the netting to install, irrigation soaker hose has been laid and seedlings have been planted. The narrow access path at right was excavated as a shallow trench and filled with barkchip from a nearby felled tree. The lengthwise border at left will be made into a wheelbarrow-accessible path.

Minimise path, maximise growing space

Keeping a path-to-garden ratio that maximises growing space is important. Path width depends on whether only a narrow foot track is needed to access the garden from one side, and to allow wheelbarrow access from the other side.

We can reach half way across the garden bed from either side, ensuring crops are accessible and to avoid walking on the garden. Were the garden bed wider, stepping stones would be installed to access crops. Alternatively, narrow paths could be built across a wider bed although care need be taken to minimise the area they consume.

Engineering thinking—the building phase

Design thinking done, it was time to move on to the other type of thinking we use in permaculture: engineering thinking. This is about the how, from what and in what quantity, and the sequence we would follow in building the garden. What is the first step, then the next, then the next. Then we build.

This phase consisted of:

  • clearing the site of the garden bed to remove rocks and weeds
  • construction of the timber plank sides by screwing the planks into short star pickets hammered into the soil—a single upslope plank and double planks downslope
  • forking the soil to open it to moisture and nutrients
  • spreading several centimetres of vege mix from the local landscaping supplier over the bed
  • spreading a layer of straw mulch
  • hammering steel posts into the soil along the edge of the garden bed at 960mm spacing and connected the tops with a curve of 25mm irrigation piping
  • looping a soaker hose through the garden; all that is needed to irrigate is connecting it to the feeder hose; the water trickles out rather than sprays
  • planting; the hexagonal biointensive planting pattern has served us well in past gardens, so we adopted it again; plant spacing relates to the mature size of the particular plant so that the plants almost touch when fully grown
  • stretching netting over the frame and pegging it into the garden soil to exclude the voracious possums and greedy pedemelons that proliferate around here and specialise in night raids on anything edible (they don’t like bean leaf or jerusalem artichoke or some herbs, but they love chives).

The stages followed the sequence of ‘what first then what next’ of the engineering thinking phase. The phase also includes working our what materials will be needed and in what quantity (planks, star pickets, barkchip, fill, mulch, soaker hose etc), and the tools (power driver, hammer, bubble level, spade) and quantity of expendables such as screws that will be needed. All these are made ready before construction starts.

The maintenance phase—how to keep it going

Now planted out, we moved into the maintenance phase—plant, harvest, replant and maintaining soil fertility.

A constraint

One of the constraints we face is that we do not produce a great deal of organic waste. This limits how much compost we can make. It is a constraint that other small households face.

Perhaps we will resort to planting a seasonal nitrogenous and fibre green manure to add nutrients to the soil, as we did on the mainland.

So, garden bed one finished. More to come.

The garden completed. To create a level planting bed on the slope, two planks or reused timber were screwed to star pickets on the downslope, a single plank on the upslope. The wheelbarrow gives an indication of the path width that is designed to accommodate it. The next door neighbours started their own vegetable garden as soon as they moved in recently. Vegetable gardens are common in Tasmania. The garden bed is the first of more to come.
We established the root crop, jerusalum artichoke that produces edible tubers (the tall sunflower-like plant), tomato, bush beans and a trial planting of the edible leaf, basella (Basella alba, aka Malabar spinach, Ceylon spinach) by one of the rainwater tanks. Basella is a warm climate crop we are familiar with from our work in the Solomon Islands and that we grew in Sydney, so we wait to see how it goes in the colder Tasmanian climate.

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Ideas, analysis and stories about the permaculture design system

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Russ Grayson

Russ Grayson

I'm an independent online and photojournalist living on the Tasmanian coast after nine months on the road in a minivan.

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