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A wave of soil with floating pots: mound gardening with knolls

Since I've seriously begun to zero in on what I want,  the sense of what I'm doing becomes clearer -- at least to me.
My template is mixed vegetable gardening -- cropping a large number of different vegetables  in the same space.
To do this in the sub tropics and be imbued with the design logic of cottage gardening isn't a straight forward exercise because I'm growing a lot of unknowns.  If I was simply planting standard kitchen garden  fare I'd have some idea of what any one plant will or should do, but when you chase an eclectic mix of exotics --with many of them being vines --  the medley is sure to be a surprise. 
In the traditional cottage garden, you layer and mix the plants by height. But in our warmer climate such certainties are undermined because of my preference for climbers, creepers, ramblers and tubers. I'm not into look -- despite the flowers -- so much as cohabitation. Planting and growing is about pushing and exploring the envelope.
En route you lose some of your soldiers...
But with each success -- and with each disaster -- the garden speaks to you.
Let us not presume that I am in control. Nor am I so smug to answer in the affirmative the question, "are we there yet?"  The truth is that I have no real idea where I'm going.
It's improvisation -- a layering of what seems to be a succession of good ideas at the time.
This means I don't so much have one garden but several. Last year's. Last season's. Last month's. This week's...
While I've pursued many projects in this kitchen garden in way of experimentation, the overriding handicap of  building it on sterile sand has forced me to be relentless in pursuit of moisture. If I had my time again, I'd start off differently by digging long trenches and filling them with manures before building the garden beds on top. Hindsight is useful like that, but once you are away you make the best out of what you've got....5 years later on. 
But I keep returning to past activities and tweaking and re-applying them. Of late I've seriously gone back to harnessing my garden paths as mulch sponges. I keep layering paper and cardboard on the paths and throwing cut stuff on top, so that they become squishy. I may walk along each path only occasionally so it's not as though they're thoroughfares for traffic.
The irony is that rather than build up the beds, I dug down the paths. In sand you can do that.
While there is no pressing drainage need warranting raised beds -- I'm thinking that I should revisit the option. I'm not planning to raise the beds so much as add mounds to them.This is a Melanesian gardening habit, and the logic is beginning to register with me.
If I add mounds to the beds -- knolls -- I increase my ground surface area, and engineer an inclined plain down which plants can tumble or ramble without necessarily wallowing in damp. I'm finding that many of the plants I'm growing don't so so well on a flat surface. I've also worked out that if I locate a terracotta watering pot in  the core of the knoll (like a volcano's vent) I can more efficiently irrigate the knoll than I  would be able to do a flat garden bed.
According to the above graphic, this works. It works on paper....
So, in a sense, I'm thinking of raising up my terracotta pots as though they've been elevated by a wave of soil -- upon which they'll float.
I hate to say this as it seems bizarre, but my experience with  mound gardening, thus far,  suggests that plants have more choices. They can go up or down. Drink by going deeper or chasing the falling contour of the soil surface. Fruiting bodies resting on the sides of each knoll are less prone to fungal infection and rotting. Inside -- within the knoll/mound -- there is more room for tubers to grow and/or go deeper.And like a box of choclates, you can invest your knoll with different centres: rotting wood, manures, kitchen scraps, dead and buried cane toads.
While the mounds will work by dint of contour design alone, the embedded terracotta pots make for a stunning hardware addition. As a centerpiece, the pots' moisture offerings are more accessible to more plants  so that their irrigating area increases.
The troughs between the knolls also serve to collect water as they function as gulleys. And running the length of each bed are the moisture retaining mulch sponge paths.
Now all I have to do is find -- or make -- the 'soil' to make these knolls places they have not existed before.One garden bed at a time.

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Comment by Dave Riley on May 17, 2015 at 0:24

As a matter of update interest. I created a new bed yesterday with this design in mind.


Since it was on verdant sand I thought I'd really get creative so I dug a trench the length of the bed and laid down two old tree trunks -- approx 8 inches/20cm diameter-- on the bottom, along its length.

I then dropped atop of this a thick layer of cow manure, before filling the hole in.

I then built up the bed and created 2 knolls with sand ("soil") I mind from the chook pen.

The chook pen is my excavation site.

I then inserted a terracotta pot inside each knoll and covered the bed thickly with grass clippings.

Two hours work. Instant garden bed.

I then planted the knolls out with seed potatoes.


I'm trying to synthesize my experience of sand gardening and utilize my knowledge of terracotta pot irrigation.

Chooks and chook poo:

After attempting various methods to harness the fertilization quotient of my chooks I decided that the best approach was simply to steal the earth under their chicken feet.  I'm assuming it has some soil qualities -- what with living  beneath chook behinds for a few years -- so I can grow plants in it.

I've built up a few beds with this sand I've excavated from my chook pen. In my system -- all the kitchen scraps, garden weeds, uprooted old vegetable plants -- indeed anything edible -- go to the chooks.

I never compost. Too much work.

Two chickens can eat a lot. While they are ravenous eating machines it isn't so easy chasing their manure which I'd have to handle carefully anyway for fear of burning my plants. So I keep moving the chook house (a wire A frame, covered in tarpaulin) around the pen...and just harvest the top layer of sandy soil.

The new bed required 4 wheelbarrow loads.

Tree trunks:

I collect tree offcuts whenever I can. While I use them in the garden for edging and as mini microclimates, I have to keep moving them about often so that I don't get over-infested with termites. I've also started burning aged timber like this to create wood ash to spread on the garden beds.

I also bury these logs as a core skeleton for garden beds. This is a Hugelkultur modification which I hope acts as a sponge to hold water near the surface despite all the sand.There serve as the textured 'bottom' of the garden bed.


After years of experimenting with manure I worked out that the best way to use it was to bury it. You can either do this vertically  -- by Honey Holing/Fertility Sponging -- or you can adapt the method used by 19th Century intensive French market gardening -- La Culture Maraîchère -- and bury it in trenches.

So that's  what I've done.

My garden bed sits on a river of poo and burying it this way ensures I don't waste the resource.

Potting up:

Like dressing a Xmas tree, inserting a terracotta pot like a volcano flu completes the design.I usually fill these only when the plants indicate they may need more watering. While the pots irrigate the knoll, the valley depression between the 2 knolls serves as a sort of swale which I'll plant out with garden greens and other annuals.


As the manures compost the surface contour of the bed will drop. And later as the tree trunks rot, the ground level will fall further.In response I can top up the sand cover or simply deepen the terracotta pots.

My assumption -- my working hypothesis -- is that the biota of the soil will do my work for me. I've found that it's the organisms in the soil who'll do the spreading and converting for you. They do a much better job of mixing soil and sand than I could ever manage by hand.

 I've sifted sand and dried manure 1:1 before, and it's hard work.

Any plants I reckon can work out their own lifestyle. The roots can go where they please or not please. If the manure layer is too 'hot' they'll keep their distance -- but the French La Culture Maraîchère   worked wonderfully without the spreading of manures or of composting them.

Also the layer of tree trunk and manures will serve as a water sponge that should have pooling 'wicking' effects.


Once fully planted out I get to see if the whole shebang works....

At stake are all my years gardening on sand and whatever I may have learnt en route.

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