Guide to Growing Marijuana with LED Lights

Guide to Growing Marijuana with LED Lights

When you set up an indoor or greenhouse weed grow room, counting on daylight is unreasonable. However, weed is a plant just like others, so it needs much light to grow, develop, and mature. Light is a vital component of weed’s photosynthesis, and you as a grower need to take proper care of providing sufficient light to your plants.

As a rule, cannabis growers have been using high-intensity discharge (HID) lights for their grow rooms but buying the whole set of lights even for a small plantation may be too costly for a layperson. Thus, LED lights have gradually gained traction in the weed growth business, as they combine affordability with the correct number of lumens needed for growing weed properly.

If you want to grow weed with LED lights, look through our indoor growing guide to find everything you need for a safe, productive planting endeavor.

Benefits of LED Light Use

As we’ve just discussed, LED lights quickly won the hearts of small-scale growers because of their benefits compared to expensive HID lamps and the CFLs that were insufficient for the flowering phase. Here are the advantages of LED lights over other options:

  • Affordability. A small LED lights kit for a home garden may cost you around $200, which is much cheaper than a similar set of HID lamps.
  • Cost-efficiency. A regular LED lamp consumes way less electricity than an HID lamp would. Thus, you will receive lower energy bills.
  • Sustainability. Your LED lights will serve you much longer, with their average use time equaling 50,000 hours. To compare, a regular HID or CFL lamp lasts only around 20,000 hours.
  • Water savings. Though HID lamps are efficient, they consume much energy and emit much heat, thus causing cannabis plants to consume more water. LED lights are much gentler in terms of heating. So, they won’t dry your plants or substantially increase the temperature in the grow room.

Choosing the Equipment

Now that you’ve decided to use LED lights in your grow room, you might be wondering, “what are the best LED grow lights for cannabis?” In most cases, it’s about the wattage of lamps, not about the brand, as most LED lights possess the same properties and can do a good job for you if properly chosen and set up.

LED lights lamps

  • If you’re a micro-grower with 1-2 plants to care for, your LED grow light shouldn’t exceed 25 watts.
  • If you have a grow room of about three by three feet (suitable for four plants), it’s necessary to give them around 100 watts of LED lights, increasing to 160 watts by the flowering stage.

Besides, it’s necessary to choose the LED lights in accordance with their grow light spectrum measured in micromoles. Weed is on the higher end of the grow light need, so you will need around 800-1300 micromoles to grow your plants to their fullest potential.

Recommended seeds for indoor growing

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Cereal Milk Seeds by Crop King Seeds
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Setting Up the LED Lights

Now it’s time to arrange the grow room equipped with LED lights. Here comes the most crucial issue – that of distancing your plants from one another and the lamps. How far should LED light be from weed plants? As a rule, lights below 300 watts should be positioned 30-70 cm away from the plants, while lamps with power exceeding 300 watts should be 70-80 cm above the plants. Still, leave some space for flexibility in the lamps’ positioning, as weed needs more LED light during the flowering stage. So, you will need to lower the lamps for the flowering period.


You can grow marijuana with LED lights like a pro with all these tips, maximizing your yield and reducing your garden’s dependence on daylight. Choose your LED lamps carefully depending on your grow room’s size and the number of plants you have. Besides, don’t forget to adjust the distance depending on your plants’ growth stage and monitor their response closely to avoid light burns and yield losses.

How many LED watts per cannabis plant are needed for effective growth?

As a rule, the amount of LED wattage per cannabis plant depends on the distance of planting your garden. A rule of thumb is to provide 32 watts per square foot of your grow space. Thus, if you have an area of two-by-two feet, you need to provide at least 120 to 140 watts of LED light. If the territory is two by four feet, the LED light wattage should range from 240 to 300 watts, and so on.

When to put cannabis seedlings under LED light?

LED lights can be of value during the initial growing stage – that of seedlings. However, while you might be tempted to speed up seedlings' development with intense light, it's, in fact, harmful to the plants. Seedlings are too vulnerable, and too much LED light can burn them and dry the soil too much. Thus, it’s imperative to use subtle LED lights until the plants mature. Intense LED light will help only when the plants reach the vegetative stage of growth and development.