Plant Cultivation

Grow Light Distance – How Far to Hang LED Lights from Plants


How Far Should LED Grow Lights Be from Plants [Explained] 

Light is an essential factor in the growth and development of plants. It fuels the process of photosynthesis, enabling plants to produce energy for their metabolic activities. However, how far should LED grow lights be from plants? This is one question that numerous plant growers have since this LED light distance affects factors such as light intensity, spectrum penetration, and overall plant health. While some of you hang the light very high and some place the light too low, this article will explore the ideal grow light distance so that you can optimize plant growth and achieve successful indoor cultivation outcomes.

Table of Contents

Factors to Consider When Determining Grow Light Distance 

Some of you hang the light very high, 30-40 inches from the top of the plant, as a result, the plants are very weak. When the LED grow lights are too far away from the plant, the light is substantially lost in the procedure of dispersing, and the light that actually gets to the plant surface is absorbed only a little, causing the plant to be unable to soak up adequate light to expand.

On the contrary, some cultivators hang the led expand lights very close to the plants, therefore, the plants on top are stressed out. Hanging the light too high will throw away light, and hanging too close will hurt the plants, so how do you make the right decision on the LED grow light distance from plant? 

Check the Leaf Surface Temperature

Most of your plants will certainly not be burned if the leaf surface temperature stays below 29 degrees Celsius. As long as you make sure of that, you can hang the lights as close as feasible to your plants. This will not only increase the utilization of LED grow lights but likewise boost plants to soak up sufficient light to expand.

Ensure the Light Intensity - PPFD

PPFD (Photosynthetic Photon Change Density) gauges the amount of light (PAR) a plant obtains gradually. As a matter of fact, changing the grow light distance is to change the PPFD that the plant can get. 

Generally speaking, the minimum PPFD worth required for plant growth is 400μmol/m²/s, and the optimum PPFD value that can be absorbed by plants is 1200μmol/m²/s. Anything beyond that will possibly hurt your plants. 

As a result, you should ensure that the PPFD value ranges from 400 to 1200μmol/m²/s. Typically, both HPS grow lights and LED grow lights suppliers will provide PPFD maps for reference, but it would be better for sure if you have a par meter that can determine PPFD values. 

Identify the Growth Stage 

The plant life cycle is typically divided into 3 phases, seedling, vegetative, and flowering stages. Different phases of the plant call for different PPFD and specific growth light spectrum. While the specific light intensity required by different types of cannabis varies, there’s an overall grow light distance chart you can follow. 

grow light distance chart

Image source:

Seedling stage: 400μmol/m²/s, with a LED grow light distance between 24-36 inches above the plant canopy 

Vegetative stage: 400-800μmol/m²/s, with a LED grow light distance between 12-24 inches above the plant canopy 

Flowering stage: 800-1200μmol/m²/s, with a LED grow light distance between 18-24 inches above the plant canopy 

How to Determine the Optimal Grow Light Distance

With basic knowledge about the three factors that have an influence on the grow light distance, here, we’ll give a step-by-step tutorial on how to determine an ideal LED grow light distance in real cases. 

Step 1. Follow Recommended Distance Guidelines

LED grow light manufacturers often provide guidelines regarding the recommended distance between the lights and plants. These guidelines consider factors such as the light intensity produced by the specific LED model and the plant species being cultivated. It is advisable to start with these recommended distances as a baseline for the initial setup.

Along with manufacturer recommendations, it is crucial to take into account the specific light intensity requirements of the plants at different growth stages. Some plants may require higher light intensity during the vegetative phase, while others may need more intense light during flowering or fruiting. 

Step 2. Experimentation and Observation

To further fine-tune the distance between LED grow lights and plants, it is better to start with small-scale trials. This involves setting up a few plants at varying distances from the lights and observing their response to different light intensities. By measuring plant growth, vigor, and overall health, growers can identify the distance that yields the best results.

Throughout the cultivation process, it is essential to closely monitor the plant development. If signs of light stress, such as leaf burn or cannabis leaves curling up, are observed, it indicates that the light intensity may be too high or too low. Adjustments can be made by moving the lights closer or further away.

Step 3. Adjusting Distance During Plant Growth

As plants grow and develop more foliage, the lower leaves may receive less light due to shading. During low light periods, such as cloudy days or winter months with reduced daylight, it is advisable to move the LED grow lights closer to the plants. 

There are also some cannabis growing tricks that help compensate for the decreased light intensity, for example, topping outdoor weed plants is one effective way to ensure adequate light penetration for lower parts of the weed. 

By following this guideline, you can determine the optimal distance between LED grow lights and plants. This approach maximizes the benefits of LED grow lights, promotes vigorous growth, and enhances overall plant health and productivity.

Verdict on Grow Light Distance 

To sum up, the preferred grow light distance ranges from 12-36 inches, depending on which stage of growth your cannabis is in. Importantly, you should fine-tune the distance to achieve the perfect balance of light intensity and coverage through experimentation and observation. 

FAQs about How Far Should LED Grow Lights Be from Plants

  • How far should a grow light be from plants?

The distance between a grow light and plants can vary depending on factors such as light intensity, plant growth stage, and the specific plant species being cultivated. As a general guideline, most manufacturers recommend keeping the grow light between 12 to 36 inches (30 to 90 cm) away from the plant canopy. 

  • What is the best distance for LED grow light?

Truth be told, there’s no best LED grow light distance that fits all scenarios, as the best distance for an LED grow light depends on quite a few factors that are illustrated above. However, manufacturer recommendations can serve as a good starting point, but it is advisable to monitor the plants' response and adjust the distance accordingly. 

  • How far can grow lights reach?

The reach of grow lights, including LED grow lights, depends on their specific design and the angle of light dispersion. LED grow lights are typically designed to provide a concentrated and directional light output, allowing them to reach the plants from as short as 2 inches to up to 2 feet or more.

  • How far should a 1000 watt LED light be from seedlings?

As a general rule of thumb, the 1000-watt LED light should be positioned around 24 to 36 inches (60 to 90 cm) away from seedlings, but this distance may need to be adjusted based on the observed growth and health of the seedlings.


About Ciki

Ciki has been navigating the digital world of SEO for over 4 years, applying her expertise originally in the software sector before turning her attention to indoor gardening. Merging her tech-savvy background with a passion for nature, Ciki offers a unique perspective on gardening, blending modern techniques with time-honored traditions.

16 thoughts on “Grow Light Distance – How Far to Hang LED Lights from Plants

  1. Luis Perez says:

    Hi there I have a siderfarmer grow light xlg-100 h- ab in a 2×3 grow tent. I’m trying to get the distance chart for the seed veg and flower stage and Also the heat chart distance.

    1. Ciki says:

      Hi Luis,

      Are you having a Spider Farmer SF1000? If so, kindly check the chart for reference: sf1000 distance chart

      1. Aaron says:

        Can I ask when the distance says hang 24/30 inch do you measure from the top of the grow tent or do you measure from the top of the pot? Thanks in advance.

        1. Ciki says:

          Hi Aaron,

          The grow light distance means the distance between the grow lights and the canopy of your plants.

  2. william says:

    if I were to say I wanted to start some seedlings but I’m in flower with my only sf1000 what height would the seedlings need to be at 90% intensity Sorry but I don’t have a light meter I’d be thankful.

    1. marcus sammons says:

      24 to 36in is the right height.

  3. Lee Tabone says:

    Hi guys, I’m totally new to this. Looking for help.
    I got the spider farmer se5000. I’m trying to find a chart of the hanging height and brightness.

  4. Laura says:

    Just getting started. We have a Spider Farmer SF2000 in a 28″x55″ tent. Only 2 small clones at the moment, should I set the dimmer power all the way up? How far to the plants should I have them set?
    I have read all different opinions. Just wondering what the manufacturer suggests.

    1. celia says:

      Hope this picture can answer your question

      1. Mike johnston says:

        U gotta be careful when using this chart. U must adjust it a little bit at a time. Don’t just turn it up to 80% just going into vegetative or u will burn them sexy ladies. Chart will work if u adjust accordingly.

    2. marcus sammons says:

      24 to 36 in.

  5. Mark TRUJILLO says:

    What setting should your spider farmer be set at for flowering

    1. celia says:

      It depends on the model of Led grow light you are using, can you tell me the model?

  6. Dave says:

    Can I add 50 watts of uv to my spectrum without damage to my babies?, I have 3×3 tent w 2 p punch, all bushed out ready to flower.

    1. hi friend, thank you for your comment, yes, you can add UV to your spectrum, but we recommend you not turn on the uv all the time, you can on the uv at 10-20 minutes before you turn off the light. 🙂

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