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Comments on the Gardening Australia program on wicking beds


Colin Austin 4 December 2013


Technically correct but maybe missing the key point

Recently Gardening Australia run a segment on how to make a self-watering containers and people have asked me what I think.

For a start let me say that I am delighted that such a well watched program as Gardening Australia is giving prominence to wicking beds - it is very satisfying to see how rapidly they are spreading.

There is no doubt that technically the system promoted using stones covered with a cloth does work - extending the time between watering and saving water.

But my question is does focusing on water saving mean that we are really missing the key point?  I, more than most, must be more sensitive to water saving but there is a much bigger issue.

Modern agriculture is very efficient and produces a lot of food very cheaply but ongoing crops take the goodness out of the soil.  Farmers are very good at knowing how much fertiliser to apply to renew their soil to produce good looking plants but while the plants may look healthy they may not contain the critical ingredients which are important for our health.

For example plants have no need whatever for trace elements like iodine and selenium but they are essential for us. Selenium is believed to play a critical role in our DNA correctly reproducing our cells. The amount needed may be very small but they are critical.  The excess of calories but lack of nutrition in our food is causing major health problems around the world - obesity, diabetes and heart problems.

Why we need improved nutrition

I have selected just one quote form the medical profession, in this case by Georgia Clark-Albert who is a diabetic specialist but the theme is widespread.

“I remembered back to my graduate and undergraduate nutrition work, when the consensus was that if people were eating a healthy diet they didn’t need supplements. However, there have since been some changes to our diets:

• Fewer nutrients in our produce because of processing techniques.

• Faster-growing fruit doesn’t have time to develop nutrients.

• Monoculture farming practices leads to soil-mineral depletion.

• Selective breeding to increase crop yield leads to genetic dilution effect and declines in the content of protein and minerals.

• The average vegetable in today’s supermarket is five to 40 percent lower in minerals than those harvested 50 years ago.”


The number 1 benefit of wicking beds is the improved nutrition

small wicking worm bedWicking beds provide a solution by providing nutrient rich food.  They can be very simple; it is dead easy to make effective wicking beds at virtually no cost.  Just take a polystyrene vegetable box, often free from supermarkets; put a pipe down to the base and a hole in the side, fill with soil and ‘hey presto’ there is an effective wicking bed. So simple that anyone can grow their own vegetables.  Plants like Kang Kong and water cress will keep on growing with virtually no attention other than occasional watering and feeding.

Of course the key is in the soil, it must contain the necessary minerals, if the soil lacks minerals then so will the plants and so will our diet. But it is not a simple as adding nutrients, volcanic rocks provide an abundance of these essential trace minerals.   Soil biology is also needed to release the minerals and make them available to the plant while worms distribute nutrients, fungal spores and bacteria throughout the soil while at the same time making channels throughout the soil so it looks likes Swiss cheese and hold much more water.

Soil biology needs feeding; recycling waste food is a socially and environmentally effective way of feeding the soil biology which in turn increases our nutrient intake.

We need to start thinking of wicking beds as a mini eco system.  Plants and animals, (that includes us humans) have evolved together in a mutual beneficial or symbiotic relationship, plants provide us with vital nutrients and phytochemicals which are essential for our health, in return animals distribute plants seeds far away from the host plants, both animals and plants mutually benefit from this relationship.

We live in an era of astonishing technical development, smarts phones are sending terra bytes of information around the world while genetics are breaking ground in improving health, but we still depend on balanced eco systems which have evolved over thousands of years to maintain our health.

This concept of a mini eco system is the philosophy behind the development of BioPacks

I would be more than happy to see Gardening Australia focus on the soils that goes into wicking beds as they are the critical issue.

Putrification and soil breathing

However there are some technical issues with using stones in a separate water reservoir.  I have had people complaining that the water in their wicking beds goes smelly and putrid. It is important that the water is cycled so the liquid water level drops (there is still plenty of water for the plants held in the soil even when the reservoir is empty) and is then refilled, this gives a breathing action to the soil, expelling stale air and sucking in fresh air.

Using living soil as the water reservoir rather than inert stones means the roots grow throughout the bed. In particular they can go down to the base of the box and extract all the liquid water so it never goes stagnant.

I must admit I do like the visible drain hole which can be used as a sight gauge on the side of the box; this enables the water level to be adjusted by twisting the drain tube. Being able to see the water level reduces the temptation to keep on topping up with more water which is the commonest cause of failure with wicking beds.


Some people argue that stones will hold more water than soil, and there is some truth in this. Stones will typically have a pore space of about 30% - the pore space in the soil will depend on the state of the soil, but may only be 20% in a poor soil.

But if the water holding capacity is an issue, for example if the boxes are going to be left for some time between watering then it is easy to increase the water holding capacity by laying pipes or some other container such as an old water bottle, in the base of the box.  These pipes do not contain any stones or soil so 100% of the space is available for water storage, much more efficient than using the pore space between stones as water storage.

A metre of 90mm storm water pipe will hold some 6 litres of water - the size of a small bucket, which together with the water in the soil gives a significant amount of stored water.

The final key point

These issues about water storage are technical issues and should not draw attention away from the fact that wicking boxes, with the necessary soil; minerals and biology enables anyone, (i.e. people who may have no gardening expertise or are living in an apartment), to improve their health by eating their own freshly grown vegetables.