Plants need light. But this amount changes with different lights sources and different situations. And when it comes to growing plants, the difficulty tenfolds.
That’s not all-
Even the slightest miscalculation here can result in low yields and in worst cases, dead plants.
So, how many plants can you grow under different watt LEDs?
This depends on many characteristics of your light. Such as its PAR rating, PPFD, distance from the plant, type of light, etc. A 320w LED bulb grows about 6 plants generally. This will vary if your grow area and conditions are different. We have disused the lights based on types, intensity, growth type, stage, etc.
Let’s jump into the next portion and see what we’ve got only for you.
Mythbusting: How Realistic of a Metric ‘LED Watt’ is?
LED bulbs are thought to be best for growing plants. Especially for starting to grow seedlings. It saves electricity and produces less heat. HPS bulbs are also very popular grow lights. But HPS bulbs produce sounds with time. So, the efficiency is maximum for LED lights. Nonetheless, all this is not always true.
Watt is Not As it’s Printed on the Label
It is often thought that an LED bulb with more wattage will have more impact on plants. But this is not true. A 100w bulb can definitely have less useful light for growing your plan than a 50 w bulb. LED lights have electronic circuits to produce light.This circuit’s quality varies from one manufacturer to the next. The amount of light produced varies as well. A good quality LED bulb should have the characteristics we have mentioned below:
- Consistent color output through the whole lifespan
- Thermal management system for heat reduction
- Energy saving
- Emits light in 360 degrees
So just the watt written on the label doesn’t indicate how much light output you will get.
Other Terms That Actually Defines Grow LED Impacts on Plants
Some of the common terms that we often use to sort out which bulb to buy and use are dependent on its measures. These measures are used to calculate the amount of light produced, the effectivity for growth, the per area for light.
They’re as follows:
|Measures||What it means|
|Lumen||Used to determine the quantity of light emitted by the bulb. The stronger the light, the higher the lumen.|
|PAR Rating (Photosynthetic Active Radiation)||The amount of light that is usable to the plants. It is the wavelength used by plants for photosynthesis. It is specially used for growing lights as a unit to measure the absorbed wavelength.|
|PPFD ( Photosynthetic Photon Flux Density)||Per second, the number of PAR photons that fall on a given surface area. It’s your crop. Every species have their specific requirement of PPFD.|
|Wattage||It is the amount of energy proceeded by a bulb. Watts for different types of bulbs can be different. For example, a 13 watt CFL bulb is equivalent to a 7 watt LED bulb.|
Number of Plants for X-Watt of LED: 6 Ways to Understand
Well, the number of plants you grow is actually dependent on a lot of factors as you know. But for each of these factors, the wattage, PAR Rating, grow space, and the number of plants. To know how these variables change with the factors let’s see the next section.
Way 1 of 6: Based on Growing Style
Varied growth styles require different amounts of light. They are, however, all used to less intense light than plants grown outside. Houseplants that thrive under lower light levels can thrive in typical room light. But for outdoor growth plants, the best light is to go for the sunlight. It gives the most efficiency as per the style you grow a plant in.
How Many Growing Styles Growers Go for?
There are many growth styles on which the growth of plants depends. But mainly 3 are taken into consideration. They are
- the Grow Room style
We have discussed the wattage for each style along with their PAR rating and the number of plants to grow.
Number of Plants-LED Watts Recommendation for ‘SOG Method ’
The “sea of green” approach is commonly known as “SOG”. It is a low-stress strategy for growing a large number of little plants at once rather than a few larger plants. Under grow lights, the sea of green method clusters many plants in close quarters. The plants form a canopy of buds under the light as they grow together, giving rise to the so-called “sea of green.” For optimum yield, this style requires many environmental factors. Like correct pot size, light, balanced water pH, soil, etc.
To help the plants from not growing too tall many use small pots of 4-8 liters. This is to prevent the waste of vital resources. The plants should also be placed as of 1-2 plants per square foot ideally and not too concentrated. In comparison to a conventional grower, SOG growers have more plants. Typically they have 4-6 times plants in the same space.
The plants require 18 hours of light and 6 hours of complete darkness per day. It’ll be used to initiate the vegetative stage. The vegetative phase will last significantly less time than the previous phases. They last for about 4-6 weeks until the plants reach a height of roughly 10-12 inches. When the plants are roughly 6 inches tall, some gardeners move to the flowering phase of 2-3 weeks.
The watt capacity and par rating for a specific number of plants are given below for SOG growing style.
|Watt Capacity||PAR Rating (µmols/m2/sec)||Number of Plants|
|60 w – 320 w||200 – 700||2 to 4|
|320 w – 450w||300 – 750||6 to 8|
|600 w||300 – 750||8 to 10|
|1000w||300 – 750||10 to 12|
|1200 w||300 – 800||12 to 14|
|2000w||300 – 800||20|
|3000w||300 – 800||30|
Every one of the plants must be the same size and have the same amount of light requirements. The light schedule will change to 12 hours of light and 12 hours of darkness once you enter the blossoming period. The plants will be forced to expand their canopy. They focus their energy and resources on the main cola.
You can trim the branches beneath the canopy once the canopy has been built. It is to avoid wasting energy on side branch development. These trims can be propagated and used as clones in the future. Lastly, they are ready to be harvested.
Number of Plants-LED Watts Recommendation for ‘SCROG’
Screen of green (SCROG) is a technique that forms even horizontal canopies. The approach stretches the lower and upper branches across an evenly dispersed plane. It is done by raising them both up and down. Cultivators can weave branches through the mesh. This is to be done by providing a screen above the growth media. But, what screen measurement is optimum for light in SCROG?
To do this, choose four 21-inch pieces of wood and join them at a 90-degree angle with a drill and wood screws. Make an attempt to make a square wood frame. Screw eye hooks into the top of one side of the wooden square at 2.5-inch intervals. Tie lengths of string through the tiny holes to create a net of squares. Don’t knot the thread too tightly so that it has room to stretch as your plants grow.
The screen is placed 20 cm above the base and it is continued in the vegetative phase. The light is changed in the 12/12 cycle to influence the flowering stage when the screen is full. The branches should be tucked and weaved for 2-3 weeks.
It is best to keep in mind that, plant counts are typically lower in the ScrOG approach, with one plant per 2’x2′ space. Longer veg times result in canopies larger than 2’x2′. Again, shorter veg periods result in canopies smaller than 2’x2′.
Plant training is made easier with the use of screens. This results in short, bushy plants with approximately optimal lighting zone.
Now you might be thinking how many plants can I grow under a 600 watts LED light?
It is dependent on the number of plans you are growing. But ideally, 600 watts capacity LED light has a PAR rating of 300 to 750 µmols/m2/sec. And it is for 8 plants.
Here are some more watts and the wattage capacity to grow plants in the SCROG method.
|Watt Capacity||PAR Rating(µmols/m2/sec)||Number of Plants|
|60 w – 320 w||200 – 700||4|
|320 w – 450w||300 – 750||6|
|600 w||300 – 750||8|
|1000w||300 – 750||10|
|1200 w||300 – 800||12|
|2000w||300 – 1050||16 to 20|
|3000w||300 – 1050||24 to 30|
Aeration of the canopy is substantially improved by the ScrOG technique. Aeration of the growing media is greatly improved by utilizing a fabric pot. The pots should be 11l for several plants and 25l for single plants. Before re-watering, make sure the soil is completely dry.
Number of Plants-LED Watts Recommendation for “Grow Room”
Grow room has controlled lights, temperature, and moisture. Hydroponic systems for plant production are also included in a comprehensive grow room system. It guarantees that lighting and humidity levels are easy to control and maintain.
A grow room’s environmentally controlled independence is done by a sealed ventilation system. To control the temperature in your grow room, you should use LED lights. They are more energy-efficient for large spaces.
The wattage capacity for the number of plants calculator is given below:
|Watt Capacity||PAR Rating||Number of Plants|
|60 w – 320 w||200 – 700||4 – 6|
|320 w – 450w||300 – 750||6 – 8|
|600 w||300 – 750||10|
|1000w||300 – 1050||10-14|
|1200 w||300 – 1050||14 -16|
|2000w||300 – 1050||16 to 20|
|3000w||300 – 1050||24 to 30|
Way 2 of 6: Based on Growth Phase
LED lights have full light spectrum capabilities. They also have low heat waste and maintenance, and a long lifespan. LED lights are used by many farmers to aid scale plant production. Specific spectrums have a strong influence on a plant’s physiology and morphology in all growth phases. LED grow lights may effectively boost growth during a specific moment of the growth cycle.
Stages of growth can be distinguished. It is done by different needs of wattage and the amount of light by a plant. Energy output can also be easily analyzed. It is for increasing crop production with the capacity to closely monitor quality.
How Many Growth Phases Are There?
There are mainly different growth phases of a plant. Different phases respond particularly effectively to wavelengths outside of the PAR range. Among them, the main are:
- germination phase,
- vegetative phase
- flowering phase
The process of determining the optimal PAR levels is reliant on a number of elements. The most important of which are the plant’s genetics, present growth phase, and climate. You can measure the PAR level using a PAR meter. You can see them at the table given below.
Now, here’s our recommendation of Par rating and watt capacity for different phases of growth.
|Growth Phase||Watt Capacity||PAR Rating (PPFD)||Number of Plants|
|Seeding / Clone||60 w – 450 w||100 – 300||4 – 6|
|Vegetative||320w – 600 w||250 – 600||4 – 8|
|Bloom / Flowering||320 w – 600 w||500 – 1050||4 – 8|
But this measurement can vary depending on LED bulbs. Personal LED grow lights will likely have lesser lumens per watt. It makes them less energy-efficient and yields lower yields. Many lights also do not have a broad spectrum and some only have limited blue and red light spectrums.
Way 3 of 6: Based on Type of Plant
All kinds of bulbs are not best for different plant types. Supplementing the green light spectrum with LED grow lights is necessary for greenhouses. It is better than cultivating completely inside due to the availability of sunlight. So let’s see how different plant types depend on LED lights.
Plant Type 1: Royal Cheese
Royal Cheese Fast Flowering strain produces rich, icy buds. It flies through the flowering stage in as little as six weeks. It is one of the fastest available photoperiods. Their amazing shortness has won over many gardeners who generally prefer auto-flowering variety. This is for their unusually fast for a photoperiod strain.
You can let Royal Cheese plants grow to a height of 100cm and produce a lot of lateral growth if you have a big enough grow tent. They can produce a single primary monster cola as well as a slew of subordinate blooms. After only 6–8 weeks of blossoming, you can expect a yield of 450–500g/m2.
Plant Type 2: Easy Bud
Easy Bud is suitable for both rookie and experienced growers. For those who want many harvests of tasty Easy Bud buds in every season, the easy bud method is for them. Even yet, the impatient farmer will be thrilled with how swiftly the strain matures. It emits herbaceous Skunk scents in the latter weeks of blooming.
It will maintain a small stature during growth, which is one of the key reasons it can adapt to varied settings. It’ll stay around 50–60cm tall indoors, while outside plants will be able to reach 60–110cm. These plants will provide you with 275–325g/m2 indoors and 30–80g/plant outside.
Plant Type 3: Speedy Chile
Another strain under the Royal Queen’s Fast Version label is Speedy Chile. With a blossoming time of only 6 weeks, this one is incredibly rapid. Speedy Chile is a good choice for Sea of Green setups as well as continuous supply systems. This is because of its rapid cycle and evenly active structure.
This is a little plant that grows to be 60 – 100 cm tall indoors and 100 – 170 cm tall outside. The flowering season is only 6 weeks long, and the typical indoor crop is 475-525 grams per square meter. So, the plant is best grown outdoors. The harvest occurs in early September. In that month, the yields 450-500 grams of high-quality buds per plant.
The light requirement as per the space they need and the amount of yield is given in the chart below.
|Plant Type||Watt Capacity||PAR Rating (PPFD)||Number of Plants|
|Royal Cheese||320 w – 450 w||300 – 750||4 – 8|
|Easy Bud||320 w – 450 w||300 – 750||8 – 12|
|Speedy Chile||320 w – 450 w||300 – 750||4 – 8|
Way 4 of 6: Based on Light Source Distance
Different stages require different distances from the light source. You should move the LED light closer to the plant. This is to be done when plants begin to flower and produce fruit.
This is so that the plant has more light available for photosynthesis for growing flowers and fruit. If your LED lights are put too close to your plant, they will bleach and develop yellow areas.
LED lights, on the other hand, do not burn plants as much as other types of grow lights. This is due to the fact that they produce less heat. However, you should be cautious.
But, how far should my LED grow light be from my plant?
Usually, an LED grows light needs to be kept 15 to 30 inches away from your plant. The distance is to be adjusted with the growth of the plant to maintain a consistent distance. The distance may vary depending on the wattage of light, the type of LED, and the ambiance. But as a rule of thumb, higher wattage of LED light needs to be placed further away from the plant.
Why Does LED Light Source Distance Matter?
Light-emitting diodes (LED) lights are a great source of light for the greenhouse. Although LED lights have lesser heat emittance, the distance from plants can change a lot of outputs. Too much heat can burn the plants and produce burn patches. Again, less light will weaken the plan and produce lessen yield.
Because LED lights typically emit light that has both blue and red wavelengths. They’re ideal for early-stage plant growth. Also for when plants begin flowering and producing fruit. It’s because those stages of the plants’ life cycles need the most intense light and the light distance should be less. It is for optimal production of a number of plants.
How Far Should LED Light be for Seedlings Stage?
LED grow lights for seedlings should be between 25-36 inches above the plant canopy. This depends on the power (wattage) of the light source. Your LED grow light should be placed the farthest from the seedlings (36″). This is to keep the heat and light intensity low and avoid seedlings from drying out. The lights can be moved closer later. But only once the roots have formed and sprouting has begun (usually within the first 2-3 weeks).
How Far Should LED Light be for Vegetative Stage?
LED grow lights should be placed 11-25 inches away during the vegetative stage from the top of the canopy. Compared to the seedlings phase, the light source should be placed closer to the plants. This is because more light is required for photosynthesis at this stage.
How Far Should LED Light be for the Flowering Stage?
The demand for bright light lessens as the plants grow through the blossoming period. To generate flowers, the canopy’s upper leaves should be 18-24 inches from the light source. At this stage, the plants begin to grow taller and produce fruit. It is not needed to change the height of the lights during flowering. This depends on the lights and how you want your crop to grow, especially if you don’t want taller plants.
Way 5 of 6: Based on the Type of LEDs
The peak of photosynthetic efficiency is found in the red and blue light spectrums. Red light has a wavelength of about 700nm. It is one of the most effective at driving photosynthesis. Especially during the flowering stage when biomass growth is most crucial. Blue light is needed at both the vegetative and blooming stages for plant growth. But primarily for the establishment of vegetative and structural growth.
But what color light is best for plant growth?
The ideal color spectrum is determined by the sort of plant you want to grow. So the ideal color is actually dependent on the stage, light need, and type of plant. This can get rather difficult. It’s really only relevant for commercial producers that want to get the most out of their crops. Plants thrive in a wide range of wavelengths, but they don’t require equal amounts of each.
Purple LED combines red and blue wavelengths. It provides skin cleansing (blue) and anti-aging effects (red). Purple also helps to improve skin fitness and vitality. It is done by promoting cellular oxygenation and regeneration.
More blue wavelengths are present in cool white light, such as one with a color temperature of 6500K. More red wavelengths are present in a warmer white light, such as one with a color temperature of 3000K.
Red Lights and Blue Lights
The formation of chlorophyll is directly tied to the influence of blue light on plants. The stems and leaves of plants that receive a lot of blue light will be strong and healthy. Again, red light helps plants blossom and develop fruit. It’s also necessary for seed germination and growth in the early stages of a plant’s existence.
Way 6 of 6: Based on Light Intensity
The human sense of light intensity is different from the way plants use and absorb light. This is why we measure the light output for grow lights. Light intensity has a huge role in plant cell proliferation and organ attachment.
Different light intensities have an impact on plant growth at all stages. Plants don’t require a lot of light at an early stage. All we have to do now is supply the right amount of light to meet the needs of plant growth and germination. The light intensity needs to rise during the growth of the plants. This is critical for a seedling’s robustness and neatness.
This table shows the intensity of a number of plants with watt capacity.
|Watt Capacity||Intensity (lux)||Number of Plants|
|60 w – 320 w||955lx||2 – 4|
|320 w – 450w||1692lx||4 – 8|
The PPFD is in mol/m-2/s-1 or micromoles per square meter per second. It is displayed along with the “light footprint” or canopy coverage as the light intensity(lux). To measure the lumen of your room perfectly, you can use a lumen meter. It will make your calculations easier than normal. Here’s our top pick of a lumen meter.
As the distance between the light source and the plant canopy grows or decreases, the intensity, PPFD/ PAR, and “light footprint” all alter.
Can You Increase Your Light Coverage?
The lamp footprint is the coverage area ie this footage of the canopy that is under a beam of light. This is needed for the relation between LED grow light intensity and coverage area. The farther a light source is, the lesser coverage the plant will get.
Let’s imagine you have a lamp hanging from your canopy at a 1-foot distance. The hanging height is then increased to a distance of 2 feet. As a result, the light intensity will be reduced by a fourth. This is why insurance is required. The wider the distance between your lights and canopy, the larger your footprint. However, the lower the light intensity, the better.
If you ask us, we already have some of the efficient LED bulbs for a number of plants in mind. Take a look below:
Your choice should always depend on the key factors we have mentioned by far.
Here are some questions that you might still be confused about. So do take a look.
Will standard LED lights to grow plants?
Regular LED lights are not to be used as grow lights. Even though they emit some of the wavelengths required by plants. Plants demand a lot of light, and regular LED lights don’t provide it. LED grow lights are designed to optimize red and blue light, which is essential for plant growth.
How many hours of artificial light do plants need?
When grown under artificial lighting, most edible species require 14 to 18 hours of light per day. Indoor plants require more light hours than those growing outside. Don’t be tempted to leave the lights on all day. Plants usually need at least six hours of darkness each day to thrive.
Which light bulb is closest to natural light?
Halogen bulbs are a form of incandescent that produces “white light,”. It is a close replication of natural daylight. Under halogen lighting, colors are more vibrant and the lamps can be dimmed. They’re slightly more energy-efficient than incandescent bulbs. But they’re also more expensive and have a greater temperature of burn.
That was all we had to say on a number of Plants to grow with different watts of LED lights. There were a lot of ambiguous points in our article that needed to be clarified. We attempted to depict them as simply as possible. It’s a good idea to check to see whether your leaves are dying or changing color now that the LED light is in place. By this, you can be aware of any adverse effects on your plant beforehand.
Thank you for sticking it out with us all the way to the end. To stay connected and update us on your plant updates, do use the comment box below.