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The Thorny Croft Vision

by Bob Corker

Thorny Croft Blog –  Bob

This is my first blog on Thorny Croft, so a good time to give you an introduction to our vision.


Thorny Croft is approx 6ha  on the western end of the Kotare Village Home block.

Mostly flat with some south facing slopes.  The idea is that we develop a multi tiered polyculture of trees, shrubs  and pasture, that supports cows, pigs, poultry for the village.  Our bacon and egg breakfast farm.  The cows milk will support both the poultry and the pigs in the early stages, until the tree crops take over this role.  We are inspired by the permaculture vision of optimising the use of the  incoming solar energy, and maximising the root depth from which we can recycle nutrients, all the while sequestering more carbon and regenerating the soil biological matrix.  Once this progression is understood, the main challenge becomes choosing the species and cultivars, while timing the successions.  Top of the canopy will be oaks (they seem to thrive here), then walnuits, hazels, pears , apples, nitrogen fixers etc. What can’t be used directly for human food will go to the pigs. Then its about exploring variations of shade tolerant berries, herbs etc.  All creating habitat for insects and duck or chook forage.  To get inspired read Russel Smith : A permanent Agriculture (one of Bill Mollison’s inspirations) and Mark Shephard’s Regenerative Agriculture, where he demolishes the arguments that Permaculture can’t compete with modern industrial agriculture.  Increasingly what it comes down is that what is important is not production per hectare, but human nutrition  per hectare, and surprisingly he shows that well tuned permaculture systems come out on top, easily.  So no time to lose, get out and plant like your grandchildren will depend on it.  But note the phrase ‘well tuned’  –  learning new systems and creating synergy will be our greatest challenge.

“It is not enough to be well intentioned, we need to become well informed”  –  Bill Mollison

Meanwhile we need to start planning for the introduction of trees.  We’ve been particularly impressed with the tagasaste we’ve planted in the drier areas, and the research we’ve done suggests that it will handle a 60 day grazing rotation well and be very productive.  Now we need a wet tolerant substitute, maybe forage willows.

This winter we did an experimental planting of one of the southern slopes, which included:

  • oaks, acorns for ducks and pigs
  • walnuts
  • mulberry’s,  hand picked, and forage for chooks, ducks and pigs
  • Croton megalocarpus, a tall high protein chook forage
  • Alnus cordata and glutinosa, coppicing nitrogen fixers/firewood
  • Maackia amurensis, nitrogen fixing coppicing of ground durable post wood
  • various apples, pears, and figs, first grade to us, the rest for pigs and chooks.
  • Tagasaste, forage for cows, and wood pigeons *(we’ll know we’ve succeeded in perrmaculture when they’re legitimately on the menu again)

Next blog I’ll discuss the grazing management and the stock, as this will be the ‘engine’ that drives the first stage of carbon sequestering, building fertility and transition into the additional tiers.

Till then happy growing  Bob

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November 11 2013 Kay’s Garden Blog

As of this morning my summer garden is basically in,  all except for the peppers and eggplants which will have to wait another week until we get back from Taste of Auckland. Incredibly different spring to last season when we  had a frost on December 1st!

This garden is now beginning the third year of it’s life!  The soil has improved out of sight….. I’m still fine tuning the crops I choose to grow to nourish us, as I’m sure I always will, the rotation system I worked out as in the new Koanga Garden Planner is working really well, very excited about that still.

I’m now growing enough compost material to be able to apply compost on all beds every time they are planted, and I have enough compost and vermicast to make my own seed raising mix now. On top of that I have enough liquid fertiliser made for the entire summer for the garden and feel confident about making more  if needed…  I’ve made both BioSol and BioFert. I’m still applying Nature’s garden to my compost heaps and my garden when planting with side applications on heavy feeders as needed. It takes time to rebuild high quality soil… it seems there is no instant solution.

Our new berry patch looks like a wall or several walls of berries at this moment, albeit unripe as yet, and the argutas planted around the fence between the vege garden and forest garden are beginning to climb along the fence, look impressive  and are also flowering for the first time.

The forest garden is now 1 year on from beginning the plantings of support trees, and certainly looking interesting.  The tagasaste has grown the fastest of course but we discovered that you can feed rabbits on it and throw the commercial pellets away and they will do better than they did on pellets, so it’s being cut for the rabbits whilst we get more planted for them.

The blueberry patch is humming, and the comfrey patch has diversified itself into a comfrey, alfalfa, mallow, red clover and plantain patch which I’m very happy about.

indian runner

Within the forest garden there is a patch where we shut the Indian Runner ducks in each evening after the day foraging on the farm behind the cows, and they are laying very well . Duck eggs have far more nutritional value than chicken eggs so we’re working with ducks as well as chickens and my negative memories of strong tasting duck eggs in earlier years is almost erased. Perhaps the breed of duck is important, we have runners which seem to produce beautiful eggs large, nutritious but not strong! Before the days of refrigeration our commercial eggs came from Indian Runners rather than chickens.

Along with all of that I’ve been developing a perennial vege garden. The perennial vegetable books are full of hundreds of plants that can be grown in perennial systems, but I am being very very fussy. There is a difference between what it’s possible to grow in a perennial vege system, and what it’s possible to grow well enough without lots of extra work and inputs, that’s productive and high enough brix – that I want to eat! I’m not interested in lots of low quality unappetising vegetables  that require a lot of room and give back little, unless I also put a lot energy in in terms of watering and feeding.

If I have to do that I’m better off putting them in the Biointensive vege garden.

Of course this list will differ for all of us because of differing soils and climate. We have hard frosts, cold winters, dry summers and very light soils.

So far the list of crops I choose to plant in my perennial patch is quite short, asparagus, globe artichoke, rhubarb, seakale, King Solomon’s Seal, and a few day lilies for their incredible edible flowers and colour!

My favourite books this year have been:  

The old books that we keep going back to have been Weston A Price’s book Nutrition and Physical Degeneration, a must for every body,  A E Beddoe’s book Nourishment Home Grown, Harvey Ussery’s Home Scale Poultry, a must have if you are a chicken person!  We are aiming to have these in stock early next year so that you can buy them through the Koanga website.

I still think that the best perennial vege book is Dave Jacke’s Edible Forest Gardens, and the best Forest Garden book for most of us is Martin Crawford’s Creating A Forest Garden.

Our new publications this year have been significant and exciting,

The Koanga Garden Planner, for old and new gardeners alike, is a step by step system that can be used to get your planning sussed in any garden large or small, not just for the summer but also for the year and onwards from there. It’s easy to plan a summer garden, but to plan it so that it then rotates and transforms into a winter garden with crops coming out and going in in a way that actually works, together with growing enough carbon crops to have enough high quality compost that you will actually be growing soil whilst growing your food is quite a mind bender. This planner will make this possible for you.

The new Koanga Beginner Gardener Booklet was one of my biggest challenges to write…….it is written to be a simple to follow process that not only gets a beginner’s garden in but in in such a way that you will be growing healthy soil and food. It shows how you can grow $2500 worth of food over a year in 40 sq m, for a cost of $176 for the seed. If you buy the NEW 40sqm Salads Stir Fries Soups and Stews Seed Collection between now and Christmas we will throw in a free copy of this booklet which gives you all the information you need to do a good job of it.

If you are beginning to realize that food security for your family will never come from the supermarket and you are unsure how to begin at home this is the deal for you. We all need to learn to be able to grow high quality food and regenerate our soil…. This is called food security or creating resilient future… This system and seed collection will have you well down that track.


Hot off the press is our Koanga 200 sqm Urban Garden Design Booklet. This garden, which we have installed here at Koanga is attracting so much attention because it looks so amazing (thanks in part to our intern Shelley who is doing an outstanding job of implementing the design and managing the area). Small spaces are exciting to work with and we can already see that a large part of the nutritional needs of a family of 4 can be met from only 200 sqm. This booklet will show you how and give you other ideas to make it even better.

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Soil Food and Health Internship – Did you get what you came for?

Soil Food and Health Internship 2013

Food Forest  focus


Did you get what you came for?


After reading about forest gardens prior to embarking on my internship here at Koanga, I had a lot of theory and much less practical experience.

This forest garden internship has met my expectations in more ways than I thought.  Although, I still had to spend time in the food and seed gardens for part of the week, there was heaps of practical application and time spent immersed in the forest garden and nursery.  Within the 10 weeks, both theory and practical application enriched my understanding of the forest garden design process, especially pertaining to how to meet the nutritional needs of plants and trees within such a system without using chemical fertilizer applications, but using, essentially, companion planting instead.

After learning about how to find heritage seeds and trees, how to propagate by cuttings, get them to root and then grow the cuttings in starter beds, how to store scion wood, root stocks, tree guilds, forest mimicry, grafting, transplanting, nicking, budding, pruning and fertilizing (with minerals) I could grow just about anything I set my heart to!

The forest garden internship definitely provided me with a solid foundation to either take on an already existing project or establish my own project from scratch!

Thank you for all of the valuable information and experiences!


– Cody Kerr

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Throwing the BTU’s out with the bath water

Okay so on my wood fire hot water heater post I said  that we  could get up to a 30% energy saving on heating water and the hint was, what do we do after we’ve just spent so much time and energy getting it up to temperature? The answer as everybody knows is we let it run down the plughole in an attempt to heat the sewer or septic tank or whereever it is your waste water goes. Lets face it, rats and microbes should be entitled to a hot bath too! Seriously though its crazy, we just let it go, the waste!  I’ve long thought we could do better but the pattern in general has been to concentrate on generating the heat directly not on waste heat recovery, its just not as sexy as the burning wood bit. I’m always on guard against falling into the pattern of …well… falling into a pattern!  You know the old saw about when you have a hammer the whole world looks like a nail. Saw ? Hammer? What? What I’m trying to say is don’t always try to solve all your problems with those solutions you most like or are identified with. Case in point I always ask students what is the most efficient rocket stove? I get many and varied replies but the correct answer is “the one you don’t have to light” People like burning stuff so we tend to gravitate towards solutions that favor this but honestly if I can get the same result with less wood burnt then I’m very happy.  So I think the goal of using up to a third less wood for the same end result is a great one to pursue.

Of course not burning any wood to heat our water is even better and we will get to that in a future post.

Now first the concept of the heat exchanger,  the radiator in your car is a heat exchanger. Water heated by the engine is piped through the radiator, air is drawn through the radiator by the fan and the air picks up the heat from the water in the radiator and carries it away. The copper coil inside the hot water tank in my last post  on wood fired hot water systems  is also a heat exchanger, the heat in the water outside the coil passes through the wall of the copper pipe and into the water in the pipe. So a heat exchanger is a device that removes heat from one fluid and conducts it into another.

A few factors affect how well this can happen:

How good a conductor the material that the heat exchanger is made of is. Copper or aluminium would be good, whereas plastic or wood would be bad as they seriously slow the passage of heat.

The temperature difference between the hot and cold.   If we have water at 70 deg c on the hot side and 50 deg c on the cold side were not going to get as much heat transfer as if  we had 70 deg c water on the hot side and  10 deg c water on the cold side. Think of it like this, the greater the temperature difference the greater the ( to use a word incorrectly but descriptively) “pressure”.

The surface area, the larger the area of contact between the hot and cold the greater the heat transfer.

The time. The longer the hot and cold sides are in contact the greater the heat transfer.

So within reason we want heat exchangers that have a large temperature difference between the hot and cold sides , we want the exchanger to be made of the most conductive materials possible , we want the largest surface area we can and we want the fluids we are exchanging the heat between to be in contact for as long as possible.

Back to our shower.  Water flows into our hot water system at ambient temperature which will depend on where you live and time of year, for arguments sake let’s say 15 deg c. The water is then heated to a maximum of 80 deg c . The water passes through a tempering valve and comes to the shower head at a maximum temp of 55-60 deg c. By the time it hits our body and then the floor of the shower its at about 40 deg c. It then runs down the drain and is lost.  The trick is to use this 40 deg water to heat up the water flowing into the hot water tank at ambient which as mentioned is 15 deg. As a side note, in winter because the ambient temp of the water is even lower it will give us better heat recovery due to the higher temperature difference. Now that doesn’t mean it will use less energy to heat the water in winter, just that we will recover more waste heat due to the greater temperature difference. One important thing that hasn’t been mentioned and is very close to criminal is not insulating the pipe from your hot water system to where you are going to use it ,this is a huge waste of precious heat so if you haven’t done so, do so, pronto!

Now if we are using off the shelf equipment to build our heat exchanger then the humble copper water pipe is hard to beat. For a start its designed for potable (drinking ) water, its readily available and copper is a great conductor. Now the easiest system is simply to have the copper pipe feeding your hot water system take a detour along a section of your drain pipe. Typical drain pipe is around 40-45mm so the 13mm copper pipe will sit nicely along the bottom of the bigger pipe .From experience a 5 or 7 mtr length will give approx 50% heat recovery. Now don’t go getting all excited and think you can just double the length and get all the heat out.  The universe has specifically been designed so that you can’t.  As Robert Heinlein once wrote T.A.N.S.T.A.A.F.L (there ain’t no such thing as a free lunch).The energy recovery is exponential which means that the next 5 mtrs will get you an extra 25% the next 5 , 12.5% and so on.

If we harken back to one of our factors affecting heat transfer, the greater the temperature difference the greater the heat transfer. Now imagine our drain pipe with its 40 deg c water and the water in the heat exchanger pipe flowing in the same direction, the drain water loses a little heat, the water in the exchanger gains a little heat, they flow on a bit more one steadily losing temperature the other slowly gaining. What is happening to our temperature difference? All the time it’s steadily decreasing till at some point the temps are the same. Now imagine the identical situation except that the water flowing in the heat exchanger pipe is flowing the opposite or counter to the flow of the drain water. You now have a counter flow heat exchanger. This time as the drain water loses heat it encounters cooler water in the copper pipe the further it flows, conversely as the water in the copper pipe follows the drain it encounters progressively hotter water. This means we are maintaining as large a temperature difference as we can and so we are transferring more heat.


Now a few real world caveats, the first being that shower drains generally get lots of hair and stuff down them, so while having a spiral of copper pipe or some other high surface area arrangement will recover more heat it will also block more readily so be happy with the straight copper or if your a bit handy I’ve always thought it would be great to make a shower base out of an old copper hot water tank or sheet of copper with a large coil of copper pipe soldered to the back and then down the drain. Commercial units are available that have a spiral of pipe around a section of large diameter copper pipe through which the drain flows and this is ideal and can fairly easily constructed by those with access to welding equipment.

water flows

The second caveat is also about blocking but this is concerned with where and how your copper pipe enters and exits your drain pipe. If you drill the holes in the drain pipe in the top of said pipe then again it will almost certainly block due to the copper pipe hanging down into the drain so while its harder to seal its far better to have the pipe enter and exit from the bottom.

Now if your talents lie in other areas, as stated earlier commercially constructed units are available and are generally well engineered, but will cost you. If you’re like me though you wont be able to resist the temptation to tinker.

Happy Thermodynamics !