Ask your questions about Växtljus.

Växtljus is a hot topic and there are many who think the si and so but how is it
actually what says today's research? Is the red and blue lights really
so good to grow only in mm. Yes there are many questions that need
a response.

Now you can ask questions about växtljus. One of Sweden's leading researcher on the subject
Karl-Johan bergstrand at SLU will answer the questions I pick out.
I forward your questions to Karl-Johan.

The answers you will find here on my page and in the Chili Magazine which will
be available for download later this spring.

You should ask questions directly here as a comment. PS. You do not see your question
before I approved the comment.

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27 Responses to Ask your questions about Växtljus.

  1. Robert M says:

    What distance should the plant be away from the light source and how many hours in a day to wear your lights on?

    • Stig Häggkvist says:

      The distance depends on the light source, how much light and radiant heat it emits, and, of course, how the story take you want to brighten up. A distance between 30 till 100 cm is a good benchmark. the stronger the light source the higher up you can have the. Illumination duration at uppdrivning of the plants approximately. 14 – 16 hours per day.

  2. Kai Ottosson says:

    Recommendation 200w/m ², How does it with regular white LED? Is there still a 200w that apply or you can use the Lux or lumen?
    Lux, lumens and Watts is, of course, those things that we hobbyists have access to.

    • Stig Häggkvist says:

      Hi! In the case of regular white LEDs, it is still a 200w/m ². Answers about Lux, Lumen and kelvin can be found in one of the answers here, then the question has already come up. When it comes to Watts so I sent the issue to the researcher Karl-Johan bergstrand at SLU (Swedish University of agricultural sciences)

      Here are his answers:


      The short answer is that no one of them is correct.

      Ideally you should use µmol/m2/s, but because such meters are too expensive for hobby farmers, I usually recommend W to compare light sources with similar efficiency (for example,. LED, HPS and fluorescent lamps).

      100 W is for about as much light (in µmol) regardless of whether the light produced by LEDS, HPS or fluorescent lamps (HPS and LED is generally slightly higher than fluorescent lamps). Please note that we cannot count on this way with light bulbs. Lumen is very misleading, in particular, if you have light sources with very red and blue light, for reasons that I explained in the question of kelvin and lux.

      Best regards


  3. Maria Wijk says:

    I belong to the band that does not grow in artificial light, since my opinion is that they do not meet the Sun gives light spectra, and for me it works great.

    But it does not mean that I do not want to learn more about micromoles, lumens and Watts. Is there any fluorescent lamp that can give the plants as much energy as the Sun provides?

    If you grow with artificial lighting, is there any recommendation on how long the plants need to be away from light in order not to be damaged by light radiation or heat… relative to the light source (standard fluorescent, led etc)

    • Stig Häggkvist says:

      Hi! No there is no fluorescent lamps or other light source that can provide as much energy as the Sun. At our dark time of year the Sun is so far away and lights up for a short time to our plants to get enough energy and complementary light via a light source is preferable. It is only in March – April as the Sun provides enough energy for the plants to feel good.

  4. Tommy Andersson says:

    How is the equivalent of a 100watts CFL a high pressure sodium on 400 Watts?
    Low energy should have about 6500lumen.
    How does fluorescent lighting on 6500 Lum in comparison with this?

    • Stig Häggkvist says:

      100W low energy has only a 1/4 of light energy compared to HPS on 400W. Well suppose you mean K kelvin and it has no larger significance, but are the same in both alternatives you mention.

  5. Ola Westermark says:

    How effective is a high pressure sodium bulb per watt as compared to fluorescent plant lighting?

    • Stig Häggkvist says:

      A high pressure sodium lamp (HPS) has slightly higher light exchanges than fluorescent lamps. HP ca. 2 µmol/W fluorescent tubes 1.8 µmol/W

  6. Boris Karlsson says:

    Can you explain why kelvin and lumen, Lux is not important

    • Stig Häggkvist says:

      Hi! To get a good explanation to your question so I sent it on to the researcher Karl-Johan bergstrand at SLU (Swedish University of agricultural sciences)

      Here are his answers:

      Kelvin and lux have to do with the human eye, Kelvin with colour vision and lux with "bright idea". Because our pupils adapt to light so it becomes misleading to plants. Lux takes most account of green light and cover almost not at all wavelengths in c:(a) 450 NM and over 650 NM, i.e.. you miss a lot of light which the plants have the advantage of.

      Kelvin is not an absolute measure but same Kelvin numbers can be achieved using many different combinations of Red, Blue and green light, i.e.. It says nothing about the quality of the light, but just how the human eye perceives light. The human eye is a very bad light sensor.

      Best regards


  7. Jonas says:

    Almost everything I managed to find on the net about växtljus is about growing vegetables or fruits. What I understood it requires more energy than other plants. What can I possibly need anything to green and a little hardier plants?
    I want to place some plants far into the room where they don't get much light. In order to survive I must have växtljus, but is not eager to slap up 100W tube lamps in the middle of the living room.

    • Stig Häggkvist says:

      Hi! In a living room should I use trail is beautiful spots with white lights that hang over the plants. You can write a message to me via my contact page and tell us a little more about the number and size of plants you have, so you'll get suggestions on JOINT works.

  8. Daniel says:

    What color temperatures (Kelvin) is preferable when you pull up the chili and wintering? Or are there other things that come into play, for example, nm? Please write out what you prefer to use when you pull up the chili and winters.

    • Stig Häggkvist says:

      Hi! Kelvin has really no significance goes equally well with warm that cold light. I use 4000 k and 6500 k then it is most common to use. I have done tests with 2700 k to 6500 k and I saw no noticeable difference. The spectral difference is so small when it comes to hot and cold light in fluorescent lighting if you measure up. We see it, but the plants do not 🙂

  9. Gustav Almer says:

    I want to remember that you said 2700K eh too hot in another part of the blog.

    my picture huh huh 2700K to 5000K red light white light and 6500K huh Batt.

    but, then, so that Kelvin only reflects our experience and independence of the kelvin so the light can contain the wavelengths anywhere?

    they're in such cases confusing when you obviously believe that a blue light containing the blue wavelengths.

    even stranger, they were when I came upon a lamp with warm white light that was alleged to have 2700 k i.e. a light that will be perceived as red.. which is contrary to the idea that K is about how we see the light.

    • Stig Häggkvist says:

      Hi! Also I learn new things when it comes to växtljus. After many tests so I know that it is true that the Kelvin for farming under fluorescent lights has no meaning. The light reaching our eyes from the light source contains a mixture of different wavelengths. Our sight cannot distinguish the different colors, without combining them into a given composite color impression so that hot or cold light. When it comes to low-energy light bulbs or fluorescent lamps, it is the difference between warm white and cool white is usually very small if you look at the spectral curve so it doesn't matter if they grow during hot or cold fluorescent tubes.

    • Stig Häggkvist says:

      Red LED and a blue LED that contains only these wavelengths we perceive right. When the light of fluorescent lamps contain all the colors we cannot discern these colors. This with the 2700 k are red and the 6500 k is the blue is more certain to be able to sell more bulbs and old ideas that many still insist that it is so. Kelvin has no meaning in the culture context.

  10. Rickard Andersson says:

    what amount of kelvin do you recommend in the case that you should run the same lamp through both the vegetative and generative phase?

    • Stig Häggkvist says:

      You need not worry about kelvin you can run with the same 2700 k or colder light 4000 k – 6500K all the time. The spectral difference is so small so it does not matter. It's just our eyes to see the difference the plants receive all the energy they need.

  11. Therese says:

    Do not know if it's too late to write this.
    I get really confused when I look for lights.
    Mn should have at least 30 ĩmol to grow indoors, least 1600 Lux (lumen). But everyone writes different. Some printing red and blue colors such 660 NM.
    So I, that is the right new, get really confused about what I should have?

    Anything to make it as easy as possible to find the right. I want light to grow such as potatoes, chilli.keyddor and lettuce indoors. Although tomato, cucumbers and other vegetables ago. Maybe I'll go for a bigger giant expensive lamp instead of these little?

    • Stig Häggkvist says:

      Hi! do not worry about ĩmol and lux (lumen) it just gets confusing… White light fluorescent lamps, or CFLs which are also fluorescent tubes, but in another form. Calculate 100W per square meter If you have an area of ​​100×50 50W cm hand when an area of ​​200×50 cm 100W. Needed no expensive bulbs. Fluorescent lamps are the best if you want to cover a larger area as they are available in different lengths. It goes great with a standard fluorescent fixture available such as the auto parts store, etc.. The fluorescent lights I use the term 840 or 865, it is the color of light and does not really matter for the plants which will take, these pipes are common and cheap. If you have more questions, ask the 🙂

  12. Alex says:

    Hi! Now I am very confused. Last season, I drove on the lights with “White light”, Thus high kelvintal, but Kelvin does not matter for the plants? I want to run the lights when the plants are in the living room and I can not (Do not for my boyfriend) have lamps with any light. What do you recommend for lights, and need light therefore not be standing strong vittt? What is equivalent to 100W / m2 for part? How many watts should I invest in? Grateful for answers, mvh Alex

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