Experimenting with recipes: from 16 to 18 hours cycles


Dear all, I wanted to share a recent experience with digital recipes that has been terrific.
Last year, we did upload a recipe inspired in the Mediterranean weather, with light cycles of 16 hours, and plants grew fairly well but I didn’t have the impression that it was fast.

This January, I changed the recipe to light cycles of 18 hours and the speed of growth is just impressive. This is after 15 days up and running in the FC.

My question now is the following: is there a recommended max limit on light hours? Anyone here did ever try 20, 22 or 24 hours cycles?


I have no experience with the PFC yet but, speaking from general aeroponic research it seems people have a lot of success with shorter cycles (several hours of light with a short period of dark, multiple cycles per day). It may not replicate a real biome but, it might help with the speed of growth.

That’s the beauty of the PFC though. You can adjust the variables of your recipe until you get the best results. Keep in mind that speed doesn’t always mean better.


@Bkirkland thank you for your feedback. Agree, faster doesn’t mean better, but I would like to get to a point in which the PFC can grow plants faster and better :slight_smile:

@Caleb, @gordonb, @adrianlu, @JoshSinykin, @JamesO and all the nerdfarmers who have a PFC up and running, what’s your experience with digital recipes in terms of light cycles?


In general, it probably depends on the plant you’re growing as far as its light needs. Different frequencies are also needed for specific plant functions (which is why you see a lot talk of red, blue and infrared). Intensity of light also effects the way plants grow.

Instead of writing it all here, I’ll link a good reference article that can be applied to generic growth.


Cool! Many thanks for this link.


I’d agree with Bkirkland- depends on your plants! I started off with Lettuce and found a lot of information from Cornell- they used to have a hydroponic lab. I believe for the lettuce they had a 18on/6off cycle worked nicely. Ill find the link


@james yes, I have papers from Cornell’s team who works on hydroponics. Agree


I know this is an old thread, but if people come across this and want to learn more, I suggest reading up on photoperiodism.

Basically, depending on the type of crop you want to grow, the length of daylight–or, for some plants, the length of uninterrupted darkness–controls when the plant switches from vegetative growth to flowering. For lettuce and other similar plants where the goal is to get big tasty leaves, you don’t want to trigger flowering–when lettuce starts bolting, the leaves taste bad.


@wsnook this is really intersting. Will use this resource, many thanks