Substrates and pots: the foundations of your indoor grow

Substrates and pots form the inseparable duo for any successful indoor grow. Whether you cultivate in soil, coco, or hydroponics, the choice of the right substrate and container directly determines the root health of your plants. Each type of substrate has its own characteristics regarding water retention, aeration, and pH, while pots influence root development and watering management.

Why choose your substrates and pots carefully

A quality substrate guarantees a vigorous root system. Soil offers a natural approach with its organic nutrients but requires precise pH management between 6.0 and 7.0. Coco fiber, on the other hand, excels in water retention while maintaining excellent aeration – perfect for beginners who tend to overwater. For the more technical growers, rockwool allows for precise control of nutrient inputs with a neutral pH of 5.5 to 6.5.

Regarding containers, geotextile pots revolutionize cultivation with their natural "air-pruning." Roots that reach the walls dry out and stimulate the creation of new rootlets, creating a dense and fibrous root system. Classic plastic pots remain practical for their ease of cleaning and durability, especially in hydroponics where watertightness matters.

How to choose the right substrate and pot

For the substrate, everything depends on your level and your goals. Beginner? Start with a pre-enriched potting mix or quality coco. More experienced? Mix perlite, vermiculite, and peat yourself to create your personalized blend. Calculate approximately 20-30 liters of substrate per m² for a standard grow.

For pots, the golden rule: 1 liter of substrate per 10cm of final plant height. An 80cm plant will need a minimum 8-liter pot. Square pots optimize floor space, while round ones promote circular root development. For geotextile pots, choose one size up as they tend to settle slightly over time.

Frequently Asked Questions

Which substrate should I choose between soil, coco fiber, or rockwool for my indoor plants?

Soil remains the most natural and forgiving choice for beginners, with its organic nutrients that gradually feed the plants. Coco fiber offers an excellent compromise: it retains 8 times its weight in water while maintaining 20% air in its structure, which forgives watering mistakes. Rockwool, more technical, is suitable for experienced growers who master fertigation because it is completely inert and requires constant nutrient input. For a first setup, go for quality coco or a pre-enriched potting mix.

How do I calculate the amount of substrate needed for my pots based on the size of my growing space?

Allow 20 to 30 liters of substrate per m² for a standard grow in 7-11 liter pots. To calculate precisely, multiply the surface area of your space by the number of plants per m² and then by the chosen pot size. For example: a 1.2m x 1.2m (1.44m²) space with 9 plants in 11L pots will require 99 liters of substrate. Always add a 10-15% margin for eventual repotting and natural substrate settling.

Geotextile or plastic pots, which are best for good root aeration?

Geotextile pots win hands down on aeration thanks to their porous structure which allows constant gas exchange. They create an "air-pruning" phenomenon: roots that touch the walls naturally dry out, forcing the plant to develop a denser and more fibrous root system. Plastic pots, less aerated, can cause root circling. However, they remain more practical for hydroponics and automated systems as they are watertight and easy to clean.

How to properly fill and install a pot with substrate without over-compacting?

Fill the pot in thirds, gently tapping the sides to eliminate air pockets without compacting. Leave 2-3cm of space at the top for watering and never compact with your hands – the weight of the substrate and watering will take care of natural settling. For coco, pre-moisten it slightly before filling as it swells by 20-30%. With soil, gently mix with a spoon if you add amendments like perlite. A well-aerated substrate should remain spongy under finger pressure.

Can substrate and pots be reused after a grow, and how to maintain them for the next one?

Pots are easily cleaned with diluted bleach (10%) followed by thorough rinsing. For geotextile pots, a machine wash at 60°C without fabric softener will do the trick. Substrate is trickier: soil depletes nutrients and can accumulate salts, so it's best to compost it. Coco can be used for 2-3 cycles if thoroughly rinsed and re-amended with nutrients. Rockwool rinses easily but loses its structure after 2-3 grows. In all cases, visually inspect for any pests or mold before reuse.