How high above the plant tops should you hang the light?

Simple question, simple answer. Yet for anyone starting to grow plants indoor in a grow tent, it is so fundamental that we decided to expand on it in this article. Read about the advantages of LED lamps and why, unlike discharge lamps, you can safely place them very close to the tops of your plants.

The answer to the question in the title is of course always the same: as close as possible.

• However, if you (like still most growers) use classic high-pressure discharge lamps as a powerful source of artificial light in a grow box (high-pressure sodium and metal halide lamps such as HPS, MH etc.), there is one important catch. Discharge lamps are powerful, but together with light they release a significant amount of heat into the enclosed cultivation space and thus into the immediate vicinity of the plants, which can harm them.
• Therefore you must be really careful to provide enough intense light without burning the plants! That is not an easy task, especially at the beginning and even more so if you have limited cultivation space and, like every grower, aim for the richest possible yield with abundant flowering.
• When you move young seedlings under a powerful discharge lamp, we recommend hanging the lamp at first a bit higher than absolutely necessary so the plant can acclimate to the intense light in its early stage. As it grows, raise the lamp accordingly so you make full use of the light.
• How to tell that it is neither too high nor too low? For discharge lamps, the simplest way to check whether the heat is not harming the plants is to hold your hand above their tops for one minute while the light is on.
• If after a minute you feel only pleasant warmth similar to what the sun can create on your skin on a summer day, everything is fine.
• But if you can barely keep your hand under the lamp after a minute and it is no longer comfortable, then it is certainly not okay for the plants either, and you need to address how to cool the air in the cultivation space effectively.
• If you cannot use the simplest solution, which is to hang the discharge lamp higher above the tops of the plants to eliminate the risk of burning, the following options are available:
  • Taller grow tent
    • For example, the popular Mammoth Pro+ HC tents feature a 25 cm taller structure specifically so the enclosed cultivation space provides enough room for plant growth and for placing all accessories, foremost the lighting, allowing discharge lamps to be kept at a safe distance from the plant tops.
  • Cooltube
  • More powerful ventilation

• The options above, however, involve additional costs, and if you enjoy indoor growing, definitely consider the advantages full-spectrum LED lamps bring to growers, such as those made by Lumatek or Viparspectra.

• Because HPS discharge lamps need to be hung much higher above the plants, the plants naturally tend to stretch toward the light.
• Grow tents with increased height are a good solution, but if you recently bought a grow box, the best investment is clearly a modern LED lamp, with which you no longer have to worry about the question “How high should I hang the lamp above the tops?” You can wave your hand under it and look forward to a great yield. So no more waving your hand under a discharge lamp.

The point is that LEDs allow you to use the cultivation space to its maximum, and unlike discharge lamps, where you must constantly watch for the risk of burning plants, you can place LEDs very close to their tops. If you are looking for a new grow tent, taller grow boxes are a practical choice, whether you grow with a discharge lamp or prefer LED lighting.

If you have any questions about MICROGREENS, we will be happy to answer them at the usual address info@higarden.cz.

We also recommend these products:

• Viparspectra PRO Series P600 (2 990 Kč)
• Lumatek ZEUS 600W PRO 2.9 (24 990 Kč)
• Mammoth Pro+ HC grow tents (from 5 990 Kč)

Further reading:

• Growing under artificial lighting: HPS vs. LED
• Can-Fan Q-Max fans: a combination of high performance and complete discretion
• Long-awaited news: LED ZEUS PRO 2.9 and LED ATS PRO