Making up a Basic Potting Soil Mix

Making up a Basic Potting Soil Mix

Making up a Basic Potting Soil Mix

Making up a basic Potting Soil Mix
The aim of this tutorial is to show you how to mix up a good Potting Soil Mix. We are often asked by customers what to mix in their potting soil for better plants. Our advice to novice growers - keep it simple. With experience in years to come you can play around with this basic mix - but  there is nothing wrong with this Potting Soil Mix. This is what we use.

What you will need
There are a couple of things you will need to organise to follow this demonstration:

  1. Wheelbarrow, Plastic Basin (large enough for 40dm3) or Plastic Sheeting
  2. Good Quality Potting Soil 30dm3
  3. Worm Castings 2 litres
  4. Vermiculite 5dm3
  5. Bone Meal 1 litre
  6. Dolomitic Lime 1/2 litre
  7. Gardening Gloves

So let's start with making up some nice Potting Soil for those young seedlings. This potting soil is not just for seedlings, but can be used for your chilli plants no matter what stage they are at.

The first thing we are going to need is a wheelbarrow, or a large plastic basin or some plastic sheeting that we can mix around 40dm3 of soil in or on.

We will start with a base of quality Potting Soil. We need 30dm3.


Culterra's Professional Potting Soil Mix is pretty much available at most nurseries. You may have a different brand near where you live - that is ok. The most important things we are looking for is a quality potting soil that has a great moist mulchy feel with some nice chunky organic matter in it. Culterra's Potting Mix comes with added coco peat and fertilizers added, so that is an added bonus. We will be using one whole large bag, which is 30dm3.

We will empty the whole bag of Potting Soil into our mixing recepticle and add to this some worm castings. Fertilis, make a super quality worm casting. This is what we use, but you may have another brand that you can get in your area.

We will use a 1 litre kitchen plastic measurig jug to measure out the smaller ingredients.

We will add 2 litres of worm castings to our bag of potting soil.

We will add one bag (5dm3) of Vermiculite to our mix. This works out at around 1:6 or 17% of total mix. Some growers like to use Perlite, but we prefer to just use Vermiculite. We perfer Vermiculite due to its water and nutrient retention properties and the fact that it contains trace elements that perlite does not. One of the biggest issues when growing in bags is the control of water. Water retention issues will result in plants undergoing stress if high low fluctuations are too drastic. Potting soils drying out too quick will mean they need more frequent waterings, which willl lead to nutrient loss due to being flushed out by frequent watering. For more details on the differences between Vermiculite & Perlite, please read this article.

To this we will add 1/2 litre of Dolomitic Lime. Dolomitic lime is not to be confused with Agricultural Lime. Dolomitic lime contains Calcium Carbonate and Magnesium and Agricultural Lime does not contain Magnesium. So the added Magnesium is the key.

Please stick to the quantities on this as too much will make your soil too alkaline and then you will end up with plants that don't grow. So no more than 1/2 litre.

To this we will add Bone Meal. Bone Meal is vitally important when growing chillies as they are calcium hungry and a lack of calcium later on will be fatal to your grow. Calcium is a tricky one as plants do struggle to absorb calcium and Bone Meal is slow release. It takes time to break down, which is why we add it right at the beginning. A lack of calcium later on can be a disaster as administering calcium to established chilli plants is not easy.

We are now going to mix all the above ingredients together. A pair of gardening gloves may be advisable as mixing by hand is really the best way to do this. We want to make sure every inch of the potting soil is well mixed and there are no patches of Bone Meal or Lime in the soil.

And Voila! What we have is an awesome, moist and soft Potting Soil Mix that has everything your plants will need for the first month or so.

We will fill a whole load of 1 or 2 litre grow bags with our Potting Mix. You may have plastic pots - whatever the vessel, fill it to around 1 - 2 cm from the rim. Once full, hold the vessel firmly between both hands and tap down on a firm surface to slightly compact the medium. We do not want to mush it down with our hands as we want the medium to always remain airy and light - not compressed. We want to have air pockets in this medium, which will also help with excess water run off and will allow the seedling roots to expand without hindrance.

Next we will show you how to plant on your seedlings with this Potting Soil Mix.

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