Questions tagged [light]

Illumination, required for photosynthesis. Use this tag for all questions about the required light levels for your plants. For questions specifically about artificial lights use the [led] or [grow-lamp] tags. For questions directly about the Sun and its effects in different conditions on plants use the [sunlight] tag.

Virtually all plants require light to power the chemical reaction known as photosynthesis, to produce sugars and cellulose (exceptions include some rare orchids such as Hexalectris which are at best partially photosynthetic).

Different plants have adapted to require different amounts of light. For example, trees that grow at high latitudes are generally adapted for poor light conditions, and low latitude desert plants are adapted for high light conditions.

There can be artificial light sources like lights or beside the natural source of light: .

Use this tag for all questions about the required light levels for your plants. Use it with tag(s) specific to the plants in the question.

132 questions
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Does it matter when I supplement light?

So i know my plants aren't getting enough light, my question is, does it make a difference if I turn on the light as soon as the direct sunlight goes away or if I do it when I get back from work (and the sun has been gone for a while)
geermc4
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Is a full spectrum 380-840nm white phosphor LED suitable for growing plants?

I am an avid grower and like most I have spent much time and money on various lights and techniques. Take a look at this http://www.alibaba.com/product-gs/1519924202/High_lumen_phospher_100w_380_840nm.html Now even if it was crap, it is cheap and…
Lewis
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Comparison of efficiency of different light colors / spectrums

I am building an led light for my indoor hydroponic / aeroponic / foggaponic hybrid herb garden. I am currently using a 100W warm white LED module. It works fine but I am also building another RGB light and that got me thinking that since plants do…
DominicM
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T5 AgroLED, Hortilux PowerVEG FS + UV, UV and Mold

I am growing microgreens and wheatgrass and sometimes run into trouble with mold. I have read that mold can be controlled by using LED lights but I cannot seem to find anything more specific. I assuming that the mold control comes from the UV. Now…
user16528
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Will this 20,000k LED bulb function as a grow light?

I see a 20,000k (color temperature) 12 watt LED E27 bulb designed for coral, aquariums and such. 7000k is supposed to be full-spectrum light, I hear. So, I imagine a 20,000k would be even more full-spectrum. I realize 12 watts isn't going to be as…
Brōtsyorfuzthrāx
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What's the difference between a regular white light bulb and a grow light?

I know that LED bulbs can vary along two important dimensions, lumens and "temperature." In particular, the temperature is important to make sure the plant gets the frequencies of light it needs. One source I read said As a general recommendation,…
Stan Shunpike
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What wattage of LED full spectrum grow light is best for ferns?

What wattage of LED grow light is best for ferns?
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How do grow light work?

I ordered grow lights and I never put thought into it until I got bored. But the ones I ordered (found Here) use blue and red LED's for light. What role does the Blue and Red light play for plants? Also I noticed how it has what the 2 colors do for…
Ljk2000
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Upper limit on light intensity?

What is the upper limit on the light intensity for growing plants indoor in a hydroponic system? Except my electricity bill off course :-) e.g. Are 1000W HPS light per sq.m. ok, as long you can keep the heat under control? Or what happens when I…
Den Uil
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Photometry and plant growth

What unit of photometry is used to assess plant growth? Is there a catalog that lists plants and the required light exposure? I'm looking at more detailed indicators than "a lot of light" or "not too much light".
neydroydrec
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How does plant size and shape change with different levels of light?

For a plant species that is described as "full sun to full shade", what differences might I expect to see if I plant it in full sun vs full shade? If you need a specific example plant, I'm writing this because I'm trying to place an American…
Empiromancer
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