How Many Cannabis Plants Per Square Foot?
HOW MANY PLANTS CAN I GROW PER SQUARE METER?
Before you get your grow on, you need to have a plan and a timetable. First, you need to establish the size of the available grow space. Hydroponic grow tents come with exact dimensions on the box. However, if you are building your own grow box, or converting a whole room into a grow-op, you need to first take measurements. Next, you must decide how much light you can put down while still maintaining optimal environmental conditions. We will breakdown the key factors to consider when choosing grow lights a little later.
Perhaps the most important question the grower needs to ask him/herself is; how much time can I commit to cannabis cultivation? Work, family, and social commitments can make growing a difficult balancing act. A large sativa plantation will be far more time-consuming to maintain than a couple of autoflowering plants in a wardrobe.
The genetics you choose and your preferred grow style will ultimately determine how long it takes to bring your crop to harvest. Precisely how many plants to grow is a personal choice. But the following will help you discover your indoor marijuana magic number.
2. Screen of Green (SCROG)- 4-6 sq/ft per plant
Growing in the SCROG style creates a lush carpet of leaves that’s visually similar to a SOG grow, but instead of consisting of tons of tiny, young plants, SCROG involves the use of a screen that directs the heads of mature vegetative cannabis plants into equally distributed patterns. Cannabis plants are very pliable, which makes it easy to direct the growth of the tops of your plants into empty areas of your screen.
Some growers find SCROG to be easier or more effective than SOG, but if you try this grow method, you’ll be much more limited when it comes to the number of plants you can fit into a square foot. SCROG naturally creates massive cannabis bushes, and each of these bushes can take up between 4 and 6 square feet of growing space.
3. Topping- 2-4 sq/ft per plant
This growing method is often used in conjunction with SCROG, but it can also be done on its own. In contrast to SOG and SCROG, topping doesn’t require huge numbers of plants or any special equipment; as your plants grow, you simply cut off their tops after they reach a certain height.
Instead of regrowing the single top that you cut off, your cannabis plants will grow two tops in its place. You can repeat this process as many times as you want; it doesn’t significantly harm your plants, and it creates many more flowering heads than you would have had if you just let your plants grow normally.
Keep in mind that you may end up needing to support your plants as they flower if you take this approach; without a screen in place, the huge colas that your topped plants grow may cause stems to droop or break. Topped plants generally take up about 3 square feet each.
4. Low-Stress Training (LST)- 2 sq/ft per plant
Another method of maximising light penetration for optimal plant development and flower size per square metre is low-stress training. Unlike high-stress methods like topping and pruning, LST manipulates the whole plant to grow more efficiently.
LST encourages more intense light penetration to the plant's lower lateral branches by preventing shading. Usually, slower-developing branches respond by growing more and developing more bud sites. At the same time, as the main cola is bent lower, a more homogeneous plant is grown.
Simple equipment is all that’s needed for LST. Soft gardening wire, string, or a packet of plant ties are each as effective as the other. It helps to drill a series of holes into the pot edges to provide an anchoring point.
Beginning as of when plants are young, bend the top of the plant horizontally. As branches fight for apical dominance and reach for the light, tie them down as well. Continue until the grow space is filled to your desire.
The vegetation time is shorter as the plant has no need to recover from the stress of topping or pruning. Thought needs to be given to the extra volume a trained plant will achieve. With less plants per square metre than SOG, but more than ScrOG, LST is the patience vs space compromise.
One or two big, sativa-style plants like a Super Silver Haze, or four to six indica-style plants like Gorilla Glue should fit in the space of a m². Just make sure they all get good light and air circulation.
HOW MUCH LIGHT DOES NEED?
It’s not as simple as purchasing as many of the most powerful grow lamps you can get your hands on. Every grow space is different. But two factors always need to be tightly controlled and constantly monitored. Temperature and relative humidity (RH) are the key environmental conditions the indoor grower regulates. You need the right tools. Invest in intake fans, extractor fans, and if available, air-con or heating.
HID lamps are a great source of illumination for the grow room and still favoured by most professionals. Unfortunately, MH and HPS lamps run hot and will significantly increase your power bills, too. One 400-600W bulb per m² is a good rule of thumb. Although, you may need to scale down to a 250W bulb. Consider improving side reflection with Mylar sheeting if you can’t keep temperature and RH dialled-in. Using high-powered old-school lighting necessitates the use of more powerful fans and possibly air-con, or else the grow-op may run too hot.
HID LIGHTS—HPS & MH
The effective light footprint for the different wattages of high intensity discharge lamps are as follows:
150W: 60 × 60cm
250W: up to 80 × 80cm
400W: up to 1 × 1m
600W: up to 1.2 × 1.2m
1000W: up to 1.5 × 1.5m
The easiest calculation for HID lighting is to divide the wattage of your light by 75 (with fractions rounded up). For example:
150W HID ÷ 75W = 2 plants
250W HID ÷ 75W = 3.3 or 4 plants
400W HID ÷ 75W = 5.3 or 6 plants
600W HID ÷ 75W = 8 plants
1000W HID ÷ 75W = 13.3 or 14 plants
Modern LED grow lights run much cooler and more efficiently than HID. The main drawback with next-gen LED is the substantial investment required for a decent high-quality kit. Over the long-term, you can recoup with the savings you make on the power bill. Choose your LED kit carefully as not all LED’s are created equal. At present, 3W diodes and COB appear to be the most promising technologies. Less heat and more usable light per watt can also save you some money when it comes to selecting fans to regulate airflow.
watts per coverage area
CFL can only take you so far. Sure, they are economic and efficient, but only to a point. In this writer’s opinion, cool white CFL is fine for vegetative growth and rooting clones, but nothing more. Using CFL’s alone for the bloom phase is not recommended. However, adding CFL as a supplement to HPS during bloom can be a winning combination.
These types of light sources only have a minimal effective footprint and only illuminate the area immediately under the bulbs. The distance to the canopy should be as little as 5–10cm while the whole plant needs to be within 30cm of the bulb or it will be outside of the effective range.
Before you get your grow on, you need to have a plan and a timetable. First, you need to establish the size of the available grow space. Hydroponic grow tents come with exact dimensions on the box. However, if you are building your own grow box, or converting a whole room into a grow-op, you need to first take measurements. Next, you must decide how much light you can put down while still maintaining optimal environmental conditions. We will breakdown the key factors to consider when choosing grow lights a little later.
Perhaps the most important question the grower needs to ask him/herself is; how much time can I commit to cannabis cultivation? Work, family, and social commitments can make growing a difficult balancing act. A large sativa plantation will be far more time-consuming to maintain than a couple of autoflowering plants in a wardrobe.
The genetics you choose and your preferred grow style will ultimately determine how long it takes to bring your crop to harvest. Precisely how many plants to grow is a personal choice. But the following will help you discover your indoor marijuana magic number.
Popular Grow Styles
Here’s some background information on four of the most popular cannabis growing methods:
1. Sea of Green (SOG)- 1 sq/ft per plant
The sea of green technique is all about curtailing vegetation time as much as possible while maximising yield and grow space efficiency. A large number of small plants is the goal, rather than fewer larger plants.
When growing from clones, as little as ten days vegetation are allowed after the clones have rooted. With standard photoperiod and feminized strains, only 3–4 weeks vegetation is required. The ideal scenario is to grow many singular large colas with minimal lateral and understory growth.
Pot sizes are kept small—with 11 litres being the maximum—where tall square pots are preferred over larger yet inefficient and shallow round pots. This allows for a maximum number of plants—typically 8–16—per square metre.
Plants are trimmed to control shading of their neighbours, and shaded lower lateral branches that don’t receive much light are removed. This encourages all the plant's energy to be directed to the larger flower clusters in full light.
With such a short turnaround time, SOG is ideal for smaller spaces like cupboards. With a mother plant and a separate vegetation space, the next lot of plants can be put into flowering the moment the present batch is harvested.
Here’s some background information on four of the most popular cannabis growing methods:
1. Sea of Green (SOG)- 1 sq/ft per plant
The sea of green technique is all about curtailing vegetation time as much as possible while maximising yield and grow space efficiency. A large number of small plants is the goal, rather than fewer larger plants.
When growing from clones, as little as ten days vegetation are allowed after the clones have rooted. With standard photoperiod and feminized strains, only 3–4 weeks vegetation is required. The ideal scenario is to grow many singular large colas with minimal lateral and understory growth.
Pot sizes are kept small—with 11 litres being the maximum—where tall square pots are preferred over larger yet inefficient and shallow round pots. This allows for a maximum number of plants—typically 8–16—per square metre.
Plants are trimmed to control shading of their neighbours, and shaded lower lateral branches that don’t receive much light are removed. This encourages all the plant's energy to be directed to the larger flower clusters in full light.
With such a short turnaround time, SOG is ideal for smaller spaces like cupboards. With a mother plant and a separate vegetation space, the next lot of plants can be put into flowering the moment the present batch is harvested.
2. Screen of Green (SCROG)- 4-6 sq/ft per plant
Growing in the SCROG style creates a lush carpet of leaves that’s visually similar to a SOG grow, but instead of consisting of tons of tiny, young plants, SCROG involves the use of a screen that directs the heads of mature vegetative cannabis plants into equally distributed patterns. Cannabis plants are very pliable, which makes it easy to direct the growth of the tops of your plants into empty areas of your screen.
Some growers find SCROG to be easier or more effective than SOG, but if you try this grow method, you’ll be much more limited when it comes to the number of plants you can fit into a square foot. SCROG naturally creates massive cannabis bushes, and each of these bushes can take up between 4 and 6 square feet of growing space.
3. Topping- 2-4 sq/ft per plant
This growing method is often used in conjunction with SCROG, but it can also be done on its own. In contrast to SOG and SCROG, topping doesn’t require huge numbers of plants or any special equipment; as your plants grow, you simply cut off their tops after they reach a certain height.
Instead of regrowing the single top that you cut off, your cannabis plants will grow two tops in its place. You can repeat this process as many times as you want; it doesn’t significantly harm your plants, and it creates many more flowering heads than you would have had if you just let your plants grow normally.
Keep in mind that you may end up needing to support your plants as they flower if you take this approach; without a screen in place, the huge colas that your topped plants grow may cause stems to droop or break. Topped plants generally take up about 3 square feet each.
4. Low-Stress Training (LST)- 2 sq/ft per plant
Another method of maximising light penetration for optimal plant development and flower size per square metre is low-stress training. Unlike high-stress methods like topping and pruning, LST manipulates the whole plant to grow more efficiently.
LST encourages more intense light penetration to the plant's lower lateral branches by preventing shading. Usually, slower-developing branches respond by growing more and developing more bud sites. At the same time, as the main cola is bent lower, a more homogeneous plant is grown.
Simple equipment is all that’s needed for LST. Soft gardening wire, string, or a packet of plant ties are each as effective as the other. It helps to drill a series of holes into the pot edges to provide an anchoring point.
Beginning as of when plants are young, bend the top of the plant horizontally. As branches fight for apical dominance and reach for the light, tie them down as well. Continue until the grow space is filled to your desire.
The vegetation time is shorter as the plant has no need to recover from the stress of topping or pruning. Thought needs to be given to the extra volume a trained plant will achieve. With less plants per square metre than SOG, but more than ScrOG, LST is the patience vs space compromise.
One or two big, sativa-style plants like a Super Silver Haze, or four to six indica-style plants like Gorilla Glue should fit in the space of a m². Just make sure they all get good light and air circulation.
HOW MUCH LIGHT DOES NEED?
It’s not as simple as purchasing as many of the most powerful grow lamps you can get your hands on. Every grow space is different. But two factors always need to be tightly controlled and constantly monitored. Temperature and relative humidity (RH) are the key environmental conditions the indoor grower regulates. You need the right tools. Invest in intake fans, extractor fans, and if available, air-con or heating.
HID - HIGH INTENSITY DISCHARGE
HID lamps are a great source of illumination for the grow room and still favoured by most professionals. Unfortunately, MH and HPS lamps run hot and will significantly increase your power bills, too. One 400-600W bulb per m² is a good rule of thumb. Although, you may need to scale down to a 250W bulb. Consider improving side reflection with Mylar sheeting if you can’t keep temperature and RH dialled-in. Using high-powered old-school lighting necessitates the use of more powerful fans and possibly air-con, or else the grow-op may run too hot.
HID LIGHTS—HPS & MH
The effective light footprint for the different wattages of high intensity discharge lamps are as follows:
150W: 60 × 60cm
250W: up to 80 × 80cm
400W: up to 1 × 1m
600W: up to 1.2 × 1.2m
1000W: up to 1.5 × 1.5m
The easiest calculation for HID lighting is to divide the wattage of your light by 75 (with fractions rounded up). For example:
150W HID ÷ 75W = 2 plants
250W HID ÷ 75W = 3.3 or 4 plants
400W HID ÷ 75W = 5.3 or 6 plants
600W HID ÷ 75W = 8 plants
1000W HID ÷ 75W = 13.3 or 14 plants
LED - LIGHT EMITTING DIODE
Modern LED grow lights run much cooler and more efficiently than HID. The main drawback with next-gen LED is the substantial investment required for a decent high-quality kit. Over the long-term, you can recoup with the savings you make on the power bill. Choose your LED kit carefully as not all LED’s are created equal. At present, 3W diodes and COB appear to be the most promising technologies. Less heat and more usable light per watt can also save you some money when it comes to selecting fans to regulate airflow.
1' x 1': 32 watts (~30 to 40 watts)
2' x 2': 128 watts (~120 to 140 watts)
2' x 4': 256 watts (~240 to 300 watts)
3' x 3': 288 watts (~250 to 300 watts)
4' x 4': 512 watts (~500 to 650 watts)
5' x 5': 800 watts (~700 to 900 watts)
4' x 8': 1024 watts (~900 to 1100 watts)
6' x 6': 1152 watts (~1000 to 1200 watts)
2' x 2': 128 watts (~120 to 140 watts)
2' x 4': 256 watts (~240 to 300 watts)
3' x 3': 288 watts (~250 to 300 watts)
4' x 4': 512 watts (~500 to 650 watts)
5' x 5': 800 watts (~700 to 900 watts)
4' x 8': 1024 watts (~900 to 1100 watts)
6' x 6': 1152 watts (~1000 to 1200 watts)
LED grow light height from plants
LED Grow Light Wattage
|
Distance from the Canopy
|
|---|---|
CFL - COMPACT FLUORESCENT LIGHT
CFL can only take you so far. Sure, they are economic and efficient, but only to a point. In this writer’s opinion, cool white CFL is fine for vegetative growth and rooting clones, but nothing more. Using CFL’s alone for the bloom phase is not recommended. However, adding CFL as a supplement to HPS during bloom can be a winning combination.
150 watts per plant for CFL and fluorescent bulbs.
When using CFLs, divide by 150W. If you were using 400W of CFLs for example:
400W CFL ÷ 150W = 2.6 or 3 plants
Which Should I Choose to Get the Most out of my Space?
Ok, so we know that the techniques you choose determine the amount of space each plant's needs, but which method will yield you the most?
This is a never ending debate, that again depends on too many variables to give you a de facto answer.
Experience Level
When you’re just learning how to grow, you can feel a little overwhelmed.
I recommend learning on one or two plants at a time, refining your skills and knowledge.
A technique like SOG requires you to grow a bunch of smaller plants, dividing your attention to detail up by just as many.
So if you're just starting out, try SCROG or topping your plants.
Cost
Another factor to consider when planning your garden is how much you can spend on it.
Growing many small plants vs. growing a few large marijuana plants means you have to buy more planters, soil and you’ll have to use more water.
If you're growing in a very limited space such as a grow tent, you can read more here on how many plants you can expect to grow depending on the size of your tent.
When using CFLs, divide by 150W. If you were using 400W of CFLs for example:
400W CFL ÷ 150W = 2.6 or 3 plants
Ok, so we know that the techniques you choose determine the amount of space each plant's needs, but which method will yield you the most?
This is a never ending debate, that again depends on too many variables to give you a de facto answer.
Experience Level
When you’re just learning how to grow, you can feel a little overwhelmed.
I recommend learning on one or two plants at a time, refining your skills and knowledge.
A technique like SOG requires you to grow a bunch of smaller plants, dividing your attention to detail up by just as many.
So if you're just starting out, try SCROG or topping your plants.
Cost
Another factor to consider when planning your garden is how much you can spend on it.
Growing many small plants vs. growing a few large marijuana plants means you have to buy more planters, soil and you’ll have to use more water.
If you're growing in a very limited space such as a grow tent, you can read more here on how many plants you can expect to grow depending on the size of your tent.
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