Grow Mediums – Soil

growing cannabis in soil

A lot of beginner growers choose soil when first starting out. Soil is something we can all recognise, its familiar and a traditional method for growing. Note that any regular soil bought from your local garden centre might not be good enough. Cannabis plants need a certain type of soil for it to have optimal growth. Using soil can attract more pests and may not be as optimal for growth as other methods, such as hydroponics, although it is a simpler and a more natural way to grow.

Tip: Avoid soil mixes with ‘extended release’ nutrients as this could produce too many nutrients or the wrong type at each stage of growing. 

trowel with soil

finding the best soil

Its important you start your grow with the best possible soil you can find. It will need to have a good texture, drainage, and water retention. It should have a dark, rich appearance, be loose in texture, should drain well but also be able to hold in water. The soil should not look thick and chunky. There are other growing mediums you could add to your soil to lighten it up and add oxygen, such as perlite.

For indoor growers you can choose soil that has been specifically designed for growing cannabis. You can also use this specialist soil outdoors if you are growing your plants in pots. If you are growing straight in the ground, the soil will likely be either sandy, clay, silt or loamy. Depending on the type of soil already in your garden, you can add other growing mediums or organic matter to increase to overall quality.

Organic matter is made from plants or animals that are either alive or have been decomposed. It will make quality soil, which in turn will create a quality plant. Examples of good organic matter for your soil are compost, manure, fish, kelp, coco coir, blood meal, bat guano and worm castings.

Soil can be used indoors but is generally more popular with outdoor growers. A soil mix will usually have microorganisms and extra nutrients already added, so there is no need to add nutrients during the first couple of weeks (plants will not be able too many nutrients when they are seedlings). 

cannabis seedling

making your own soil

As long as you know the ratios, making your own soil is quite easy (and fun!). The type of soil mix will change as your plant develops. In the initial stage of growth, plants will need a soil mix using equal parts perlite, turf, and worm meal. During the vegetative and flowering stage use equal parts turf, worm meal, and compost. Check the pH levels of your soil, if they are too high, you can add in some chalk to bring it back down again. 

watering plants in soil

Be careful not to overwater, which can be a common mistake with beginner growers. Giving too much water or watering too often can mean your plant will become overwatered. A good way to check when your plants should be watered is making sure the top inch of the soil is dry. Before watering your plant, be sure the check the pH level is at the correct reading, particularly if you have added nutrients to your water. The slowly add water until around 20% of it is dripping out the bottom of the plant. 

marijuana seedlings in pot