correct lighting times for fruiting tomatoes?

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Mar 8, 2011
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Ive been scouring the net for info on the correct lighting cycles for indoor tomatoes and im getting all kinds of different stuff. Im hearing 18 hours and they just start to bloom and also hearing that they need to cut back to 12/12??:confused2: does anyone by chance know the correct setting?
Tomatoes are daylength neutral, which means that tomatoes flower the same regardless of how many hours of darkness or light they receive. However, this does not mean that the best tomatoes are grown under continuous light. Tomatoes require an extended dark period for best quality because it is during the dark period that the products of photosynthesis are transported to the developing fruit, providing sweetness, flavor, and color

Hope this helps
What type of tomatoes you grow has a lot to do with the lighting. Some require more, some less.

There are some basics to remember. A total darkness of at least 10 hours per/24 will produce the best over-all fruit in terms of skin thickness, meat vs pulp, sweetness and size.

Studies have shown that interrupted darkness will cause major stunting of the growth.

It's also been proven that a 24 hour day is best for tomatoes. Extended and reduced times have been tried with the best results at 12/12. The 12/12 lighting SMOKED the other timings in over-all growth.

Types of lighting are also very important. Sure, tomatoes will grow under standard daylight fluorescents. You'll get fruit. If you also grow the same tomatoes under HPS lighting and keep all the other factors the same, a side-by-side comparison of the fruit will show less pulp (more meat), thinner skin and a sweeter taste to those grown under the HPS.

As with MJ, more light means better growth and yield.

Also, as with MJ, better nutrients means more fruit and higher quality fruit.

IMO, the best method for hydroponic tomatoes indoors is an ebb and flow system using high quality hydroponic nutrients and HPS lighting at 3 thousand lumens per/sq ft of growing area.

You can move the light up to 5 thousand lumens per/sq ft, but the increase in produce or quality isn't really worth it in costs.

Outside or in a greenhouse environment, NFT hydroponic tomatoes grow well also, but clogging of the root channels can cause some headaches.

A method used in Italy years ago works like crazy. Using hanging bags that have eyelets in them spaced at 18" and growing 12 plants per/bag with a drip hydroponic system and catch/recirculation system produces an incredible amount of tomatoes per/sq ft with great quality.

There have been millions of pages of studies done on inside and greenhouse tomato growing. You could spend a lifetime reading them.

3K lumens per/sq ft of HPS lighting will maximize your harvest weight/cost ratios and keep the quality high.
wow! thanks for the info guys. very informative and appreciated!
all correct!

i was going to say very concisely that like autos, they flower with age and dont require a whole lot of dark, 14/10 or so is fine. Call Jerry at He grows prize winning tomatoes in his shop hydroponically.

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