Making up a basic Potting Medium Mix
The aim of this tutorial is to show you how to mix up a good Potting Medium 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 Medium Mix. This is what we use.

Soil vs Medium – what is the difference?
Potting medium companies would have you believe their mediums are soil. We all refer to it as Potting Soil – It is a very common mistake that even we often make. But there is a vast difference between soil and medium. Soil is a material composed of five ingredients — minerals, soil, organic matter, living organisms, gas, and water. It is a living, breathing world in its own right. Medium is man made, by composting matter and by mixing with additives is sold as a soil substitute (medium) to use in containers and gardens.

Why use Medium?
Soil does not fair well in containers as it will compact over time, which negatively impacts plants growing in the container. Medium is designed specifically for containers as it is less likely to compact. Medium comes a close second best. But nothing beats mother natures own soil.

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 Medium 30dm3
3. Worm Castings 2 litres
4. Vermiculite 5dm3 (or Perlite)
5. Bone Meal 1 litre
6. Dolomitic Lime 1/2 litre
7. Gardening Gloves

So let's start with making up some nice Potting Medium for those young seedlings. This potting medium 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 medium in or on.

We will start with a base of quality Potting medium. These days there are quite a few different brands available at nurseries. We recommend using a reputable brand without breaking the bank :) We need 30dm3.

When buying your potting medium from your nursery, ensure you are getting a fresh bag. Unfortunately it has been our experience that many nurseries do not protect these bags from the elements when storing them and over time contents do get wet and fecund. This is never good and can be a source of pathogens right from the get go. If your potting medium bag looks faded from the sun or is heavy and feels dense – ask for a fresh bag!

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 receptacle 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 medium.

We will add one bag (5dm3) of Vermiculite to this mix. This works out at around 1:6 or 17% of total mix. Some growers like to use Perlite. This is a matter of preference and also depends on your climate. We would recommend you substitute one for the other should your summer region be a high or low rainfall zone. 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 will lead to nutrient loss due to being flushed out by frequent watering. This will lead to nutrient issues, blossom end rot and sickly plants – just to mention a few issues. For more details on the differences between Vermiculite & Perlite, please read this article.

This is an important choice. The basic rule of thumb – use Vermiculite in areas with low rainfall. Use Perlite in areas of high rainfall.

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 Medium 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 Medium Mix.