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I am planning to grow a single tomato plant Indoors. I am doing research on what grow light to invest on as a beginner. I want to know how many lumens does a tomato plant requires? If I want to grow similar flowering plants like cucumber, then what is the minimum lumens I should target for? I am interested in getting an LED light for that purpose. I have a small budget since I want to experiment first before I dig further into hydroponics.

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    The light also needs to be the correct color for chlorophyll. Many lumen of the wrong color does not work. Sun light is good ( obviously) but fluorescent and LEDs have very specific frequency outputs which can not be analyzed by eye. Oct 11 '20 at 0:47
  • I think light frequency spectrum information is more available for aquarium lights Oct 11 '20 at 0:50
  • Are you just starting them to transplant outside later, or do you plan to keep them inside and attempt to get fruit indoors? Nov 10 '20 at 9:26
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Welcome to the website. Your new project sounds like it could be fun and interesting.

I can’t give you a precise number of lumens for a couple reasons. First, I haven’t experimented. Other people have, though. If you enter “tomato light requirements” in Google scholar, four articles that look directly relevant pop up. The Glowacki and Chia references link directly to each full article. Neither the main list nor either article’s other versions link to a .pdf for Hernandez or Ho, so unless you want to pay rather nutty fees you’ll need to get those from interlibrary loan or something similar.

The more important reason there is no one answer, though, is that “it depends.” It depends most of all on what you expect of your plants. It depends also on how long each day the plants receive the light, somewhat on whether the light shines on all sides of the plant, and to a far lesser degree on the color of the light.

Like many plants, tomatoes can cope with a wide range of light intensities and survive. I’ve grown tomato seedlings in spring (figure 12 h/d) near 40o N with only light from a south facing window. They received ~180 W/m2 overall average, on only one side of the plant at a time. (https://www.pveducation.org/pvcdrom/properties-of-sunlight/calculation-of-solar-insolation). The key result was that, perhaps combined with relatively cold air, the tomatoes were leggy, very small, and as seedlings tended to die from damping off. Mere survival probably is not your goal. On the other hand a pair of 100-W-equivalent tube bulbs (1500 lm) on a timer per ~ 24 half-gallon milk carton pots grew beautiful stocky 15” tall tomato transplants.

For units I recommend you plan in units of watts since that’s what the tomato experiences. To convert a bulb’s lumens to watts you have to know how far from the average leaf the bulb is. Place grow lights close to the leaves, just short of burning them, and adjust as the plant gets taller. Having two bulbs may be important since that way most sides of each plant get reasonable light, especially if you periodically shuffle the pots. Each 24 plants also had two 17-watt heating pads. In both capital and operation, the heat may be more expensive than the lights but it matters.

For light duration and color, there are multiple relevant replies in Can plants have too much light, or do they need night/rest?. I mention those factors mostly for completeness.

Honestly, I wouldn’t worry too awfully much about the fine details. Start with some reasonable set-up then pay close attention to the plants. While both the technical details and experienced intuition are valuable, from what I’ve seen in myself and other people, watching plants in your own garden and elsewhere is the more effective teacher.

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Lumens is a measurement humans use to perceive how bright a light it, it essentially has no meaning to plants, as some of the posters before me have said already, strong lumen even 10,000 in the wrong spectrum or colour will not benefit your plants.

What you want, is sufficient amount of PAR (photosynthetic active radiation) PAR light is the wavelengths of light within the visible range of 400 to 700 nanometers (nm) which drive photosynthesis, also with a good mix of IR (infrared) and a small dose of UVA (which actually helps to activate more oils/flavor compounds in plants like Basil)

spectrum

the sun's spectrum

As you can see, the sun's spectrum is way more far ranging than an average LED light at home and as we know Tomato plants originate from South America, where temperature are fairly high and they also love the sun. Here are some resources I think would help you in terms of growing tomato plants.

https://www.ledtonic.com/blogs/guides/ppfd#:~:text=Although%20plants%20don't%20need,s%20on%20its%20outer%20leaves.

https://www.horti-growlight.com/typical-ppfd-dli-values-per-crop

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Useful search: https://duckduckgo.com/?t=ffsb&q=lumen+par&ia=web

The sun is a LOT brighter than you think, about 10,000 lumens per square foot. Gardens should receive 1000-3000 lumens per square foot. Successful gardens usually are lit at around 2,000 lumens per square foot.

I like 14 hour days for my Peppers, Chard and Bok Choy.

Looks like tomatoes require about 400-500 PAR. Surprisingly the link does not go to a place that's mostly about growing Marijuana.

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  • I guess ATF will not come for to inspect your high output growing lights today. In the 70's , ATF came to Amoco R & D checking on 10 each 1000 watt metal halde bulbs . Amoco was growing plants for possible oil production , not marijuana. Dec 11 '20 at 0:52

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