Public orchard on swales in Mill Park
Jan 2013: Overhead view of the dry site in summer.
Turning a parched neglected site into a large abundant orchard on a steep slope with swales to capture stormwater proved to be an interesting challenge at this outer-suburban community site.
Mar 2014: An overhead view of the completed orchard beds on swales snaking across the steep slope designed to slow stormwater runoff, allow it to soak into the soil and water the fruit trees.
THE BRIEF
The Salvation Army, at outer-suburban Mill Park, wanted to showcase the unused 1-acre site behind its church with some sustainable projects including a large orchard built on swales and a 60m2 Food Forest (see the story on this project here). They wanted the orchard to be a meeting point for the local community and to provide food for the free community lunches the church held several times each week.
THE SITE
The outer-suburban site had been scalped in the past with all topsoil removed. While the site received a great deal of rainfall runoff from a large car park at the top of the site, the site was extremely dry – in summer all the grass died and the heavy shrink-swell clay opened up into deep dry fissures. The few existing trees on the site were all parched and badly stunted: a testimony to the heavy clay soil’s inability to retain water on the steep slope. Ironically, plenty of stormwater from the car park rushed down the steep slope but moved too fast to soak into the soil and only caused erosion. Soil tests revealed an inconsistent mosaic of pH and soil profiles across the site that told a story of upheaval and disturbance. Subsoil was often at the top layer and the site’s heavy clay drained poorly.
DESIGN + PROCESS
Aug 2013: Preparing to sheet compost the first 40m long orchard bed.
Oct 2013: Hand digging the second swale on contour and creating an orchard bed.
The non-profit organisation had a tight budget and scarce funds so we decided to spend all of the small budget for the project on plants and irrigation rather than on earth-moving equipment. This meant digging the swales and creating the orchard beds by hand.
This budget allocation decision mean that installation of the project, which began in January 2013, would be delivered much more slowly, in stages and would rely on an army of volunteers. The longer timeline, however, worked to our advantage. As the site had no topsoil at all, the 40m long orchard beds were each sheet composted and left for a few seasons to allow the organic matter to break down and create rich soil.
Work on the site began with designing the site and determining the scope of work. A laser level was used to find the exact contour levels and these were marked and pegged out. Turning the soil began in August 2013 with hand digging the first swale.
The first job on tackling the site was to create mounded soil that would drain freely for the orchard to grow in and swales that would capture the stormwater that rushed down the hill by slowing it down long enough to percolate into the soil and water the fruit trees.
The soil that was excavated to create the swales was mounded up to create adjacent raised orchard rows. All three 40m long orchard beds were finished two months later by October.
The entire orchard marched down the steep slope in three parallel rows that were 40m long and 1m wide – a total of 240m2. After calculations by our two engineers of rainfall and the stormwater catchment area of the carpark above, each orchard row was accompanied by a swale on the upside of the slope that was 1m wide and 0.5m deep. These swales would capture the stormwater as it ran down the slope and slow the water down long enough to soak into the soil and water the orchard beds.
Normally, excavating topsoil and mounding it on top of exiting topsoil will give a good depth of friable soil to create a mounded garden bed with great drainage. But here we were working with a site that was devoid of all topsoil. Given how depleted the existing soil was, Hot Compost would have been ideal but difficult to create in the amounts needed, especially given the timeframe and manpower required. Instead, we decided to sheet compost the mounds by creating lasagna layers of well-watered straw, manure, cardboard, chipped wood and scatterings of hot compost. To the top layer we scattered a variety of Green Manure seeds including Lucerne and Fenugreek and a handful of earth filled with fungal mycelium strands for innoculation, and covered everything with a thick layer of straw to mulch the beds. Now they just needed to be fenced off for safety and left for a few seasons to break down.
“Each row was planted with ... a veritable cornucopia of heritage varieties of apples, pears, plums, quinces, medlars, apricots, nectarines, peaches and cherries.”
We returned to the orchard beds the following year in early Spring (March 2014). By now the mounds were covered with leafy lush Green Manure plants and a peek beneath the thick layer of straw mulch revealed rich soil beneath full of organic matter heaving with earthworms.
The swales had done their job and had slowed the plentiful stormwater enough to water the mounds and kickstart growth. Time to plant.
Each row was planted with 8 fruit trees at a spacing of 4m – 96 trees all up – and contained a veritable cornucopia of heritage varieties of apples, pears, plums, quinces, medlars, apricots, nectarines, peaches and cherries. Dwarf varieties were chosen to reduce the picking height at harvest time and to minimise the amount of pruning needed.
A feast for the senses!
