Ask Angus: What Growing Mix Should I Use For My Raised Garden Bed?

Ask Angus: What Growing Mix Should I Use For My Raised Garden Bed?

There are many options when it comes to a growing mix that will work in your Vegepod. Depending on the resources available to you, your budget and the amount of time you have, you can either make up your own mix or use a ready-made alternative such as bagged potting mix. If you want to keep it really simple, we recommend using a top-of-the-range potting mix that meets the premium grade Australian Standards.

The only issue with potting mixes designed for general purpose use in the garden, is that they do not always last as long as you want them to in the Vegepod. The Vegepod is a ‘Rolls Royce’ growing unit that will give you years of good growth. As such it is highly likely to outlive most readily available potting mixes unless they have been specifically formulated for long-term use in very large containers.

Get around this by simply replacing the mix every year or two, but if you prefer not to have to go to that trouble then read on. I’m going to give you a few options to create your own longer lasting mix. But first, let’s look at premium potting mix options that are replaceable every two years or so.

Premium Potting Mixes

Most modern potting mixes are made using various composted materials such as pine bark, green waste or sawdust, and these materials tend to continue breaking down over time which makes them collapse and lowers their aeration. This, in turn, tends to lower growth rates of the plants growing in them.

A premium potting mix, that has the Australian Standards logo in red, has a good blend of particle sizes and a good balance of air and water holding capacity. It also contains sufficient fertilizer to get your plants well established before you need to fertilize them again. It is, therefore, a step up from regular garden potting mixes, however, it too will eventually need replacing. A premium, top-of-the-line potting mix will only last two years max, with the fertiliser needing to be replaced after three months. Price is a reasonable indicator of quality, with a true premium mix costing $8 to $10 plus per 25-litre bag.

Why the Vegepod Benefits From A Custom-Made Potting Mix

As I mentioned, the Vegepod is a Rolls Royce gardening unit. It has been designed as a wicking (or capillary) bed i.e. the Vegepod has a reservoir of water underneath that soaks up through the soil to provide your plants with as much water as they need on demand. This is different to a normal raised garden bed that has drainage holes at the bottom. Your plants are never water stressed, as often happens in pots with bottom drainage, and because of this specialized and highly efficient watering system, the growing mix you use can be designed to maximize the efficiency of the Vegepod. I’ll give you some examples of mixes that will suit your needs at the end of this article.

How to Make the Perfect A Custom Potting Mix

⅓ Fine Particle Base

The first thing you need to ensure is that the mix is right for the Vegepod’s wicking system. For water to move upwards in the growing mix, it needs to have a sufficient amount of relatively fine particles that act in the same way as very thin straws would - sucking a liquid up against the force of gravity. Ingredients such as fine coir fibre (coconut or ‘Cocopeat’), peat moss and composted manures need to make up about a third of the mix to create sufficient wicking to get the water to the plant roots. Don’t go above a third of the volume, otherwise, you start to create a mix that gets very heavy in the Vegepod, making it harder to move (particularly when it is holding water), which can become a real problem in spots like rooftops and balconies.

Lightweight, Soil Additives

To keep the Vegepod well-aerated but still manageable in weight, I’d advise using soil additives that have a coarse particle size but low weight, such as perlite, vermiculite or composted pine bark (of particle size greater than 12-15mm diameter). There are some more unusual mineral ingredients that work well too if you can source them, such pumice, scoria, diatomaceous earth or boiler ash (of greater than 12-15mm diameter in all cases). What you want to avoid is coarse sand, because while it provides the aeration you are looking for, it is extremely heavy as are any other soil-based ingredients such as topsoil.

With the above components, I strongly recommend that you wear a dust mask when handling them. When they are dry due to dust they shed and this can irritate the lungs, particularly for anyone with respiratory conditions such as asthma.

Fertiliser

To ensure good growth you also need to ensure a continuous supply of nutrients to the plants. The type and quantity of the fertilizer you might need for your Vegepod will depend on the ingredients you have used in your mix, as well as the type of plants you are growing.

Potting Mix Fertiliser

A premium grade potting mix will include a controlled-release complete fertilizer that will feed your plants for at least three months. Your plants will tell you if they are running out of nutrients because their growth will slow down and their colour will lose that beautiful deep green and the gloss from the leaf surface. If you are using a premium potting mix, I recommend supplementing the fertiliser after several months.

Manures

Add a bit of aged manure into the mix as a natural way to boost your plants' nutrition. Cow and chicken manure are the most readily available, however, you may be able to get other types such as sheep, horse or pig. All are suitable for the Vegepod. Just remember they should not be used fresh because this may burn your plants, and could also be a health concern. Another point is that the nutrient content of animal manures will closely reflect what they are being fed, so if at all possible, use manures from free-range animals that have as natural a diet as possible such as pasture, as this will ensure no nasty chemical additives such as antibiotics, and will also ensure a good balance of nutrients.

Worm Farming

I love a good worm farm to supply quality, natural organic matter and nutrients to the Vegepods. Worm farms can be used to recycle all your kitchen scraps and provide pretty much all of the nutrients your Vegepod needs. Using 10 litres or so of solid worm castings in the mix for a small Vegepod will not only supply nutrients for several months, it will also add valuable ‘humus’ that helps to store nutrients in the growing mix. At Vegepod HQ, we also use a couple of 'worm towers’ (in ground worm farms) which are embedded in the potting mix in the middle of a medium sized Vegepod to provide ongoing nutrition. These are full of working worms that are fed with kitchen scraps that are broken down to release their nutrients after they are digested by the worms. They release pretty much the perfect balance of nutrients to replace those that you take away when you harvest your crops. And the worms also add beneficial microbes and valuable humus to your Vegepod.

Liquid Fertilisers

Liquid fertilizers are another way of providing supplementary fertilizer for the Vegepod. Whilst you can use inorganic or mineral liquid feeds such as Aquasol or Thrive, I love organic liquid feeds such as the ‘juice’ from our worm farm (diluted down to the colour of weak tea), or proprietary organic liquid feeds such as Charlie Carp. Always use the manufacturer's recommended levels if you are using a store-bought fertilizer.

Weeding Out Weeds, Pests and Diseases

Weeds, pests, and diseases can be introduced from growing mix ingredients and are an important point you want to be aware of. To avoid this, if you are purchasing ingredients such as manure or composted organic materials, make sure they are certified as free of problems. If you are collecting your own materials, look for sources that are not exposed to sources of weeds, pests, and diseases.

Angus’s Custom Potting-Mix Recipes for Success

There is an infinite array of possibilities when it comes to making up your own mix for the Vegepod but some simple mixes that I and the Vegepod team have found to work well include:

3 parts premium potting mix
1 part bagged cow manure
1 part perlite

4 parts premium potting mix
1 part perlite

3 parts premium potting mix
1 part perlite
1 part worm castings

2 parts premium potting mix
1 part perlite
1 part vermiculite
1 part worm castings

2 parts premium potting mix
1 part coir fibre
1 part perlite
1 part cow manure

A Final Word On Health & Safety

When handling potting mixes, as well as avoiding inhaling dust from dry materials by either wetting them down or wearing a dust mask, I also recommend wearing gloves to avoid infection with pathogens that may be present. Whilst the risk of infection is relatively low, anyone with a compromised immune system or respiratory problems have heightened risk and definitely should take precautions whilst setting up the growing mix.

We want your Vegepod to be the most positive thing possible for your health, and once you start getting into the freshly harvested produce it will bring in abundance you will wonder how you ever did without it.

Happy gardening!

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