The first thing to consider is the type of cannabis you’re growing—the strain genetics. Sativas tend to grow tall, while indicas are stocky and bushier. Autoflowers grow particularly short, with some varieties reaching only 50–60cm. Even those without significant spatial limitations tend to choose shorter cannabis varieties when growing indoors.
After all, you are responsible for providing illumination, so you need to account for the space taken up by your grow lights. Moreover, if you’re growing different strains and some end up being much taller than others, this can deprive smaller specimens of light, resulting in stretching and reduced final yields. If you don’t plan on training your plants, consider growing the same type of strain, or two strains with very similar heights, to avoid running into issues with spacing and lighting. Of course, the smaller and more compact your plants, the more you can fit per square metre. It’s up to you to decide if you’d rather crop several small autoflowers or just one or two ultra-vigorous hybrids. The dimensions of your growing area will largely dictate how many plants you can grow per square metre, and in general. If you’re like most home growers, you’ll likely be using a grow tent set up in a suitable location in your home. Grow tents are available in many different sizes, from small 50 × 50cm tents to large ones that could fill half your room. The right size depends on what strain(s) you’re growing, how large your indoor growing space is, and what type of grow you are going for (heavy training, leaving plants to develop as is, etc.).
As an example, if you just want to grow a single untrained photoperiod indica plant, a 1 × 1m tent should be sufficient. As you add more plants, you’ll need to scale up accordingly. But again, don’t just account for the eventual size of the plants themselves, but also lighting, ventilation, and other equipment. Depending on the diameter of your pots, several can fit into one square metre. But the size of your containers doesn’t just impact how many plants can fit per square metre, but also how big the plants will get overall. Said differently: The larger your pots, the bigger your plants will get. Recommendations for pot sizes: • ½ litre: Seedlings and young plants up to. 25cm • 5 litres: Plant height up to 60cm • 11 litres and more: Average plant height (check strain description) For the average indoor grow, you can fit nine 11-litre pots per square metre. Use rectangular planting pots to fully take advantage of your available growing area. With round planting pots, you’ll be wasting valuable space. See our planting pot calculator to find the optimal pot size for your cannabis plants. 21L - 1 plants m² 18L - 2 plants m² 15L - 5 plants m² 11L - 9 plants m² 5L - 18 plants m² 3L - 25 plants m² The environmentally friendly RQS fabric pot, complete with proprietary “Aqua Breathe” geotextile layer, lets your plant’s roots breathe for optimal growth. The environmentally friendly RQS fabric pot, complete with proprietary “Aqua Breathe” geotextile layer, lets your plant’s roots breathe for optimal growth. With plant training techniques, you can keep the number of cannabis plants to a minimum while maxing out their potential. Each of these training techniques is designed to optimise space and increase yields. SEA OF GREEN (SOG) • 4–16 plants per square metre • Outcomes: Fast yield, keeps plants short, easy to perform, comparatively smaller yields per plant. The sea of green method (SOG) is all about getting the most out of your available floor space. It is a good way to achieve a consistent outcome with photoperiod plants, clones, and autoflowers. In a SOG, plants only get 1–2 weeks of vegetative growth before they are forced to switch to flowering. As the plants don’t have time to branch out, the result is many short plants with short main colas. Under a 400W HPS light, you can fit 4–16 plants per m² in 5–12l containers.
An optimal SOG grow can deliver multiple 500g/m² harvests per year. • 2 large/5–10 small plants per square metre • Outcomes: Simple to perform, keeps height in check, boosts yield, prolongs growth phase. Topping and fimming are high-stress training methods. By cutting off or pinching the main growing tip, you break the apical dominance of a plant so it develops multiple main colas instead of just one. This naturally results in bushier growth and causes plants to stop growing in their characteristic Christmas tree shape. Any high-stress training technique that involves damaging your plants (like both topping and fimming) slows down growth and extends the vegetative phase. If you’re pruning, topping, and/or fimming, allow your plants to recover and expect a later harvest date. Don’t overdo it; top or FIM 2–3 times per growing season. • 1 large/2–4 small plants per square metre • Outcomes: Challenging to perform, consistent results, options for beginners and more advanced growers.
Mainlining and lollipopping are two plant training techniques that promote the growth of large buds at the ends of branches.