Grow lights

[Ger-annie-um]

The first of my seeds (toms, brassicas, lettuce, herbs) have poked their heads up so I need to set up my grow lights. Any advice as to how many hours a day I need to have them on for? I was thinking 14 - 16, is this enough/too much?

[history gardening]

14-16 hour fine for tomatoes and herbs. but lettuce need to be limited
8 hours max if the temps are over 75 f they start to bolt.

[mothhawk]

I don't think LED lights will raise the temperature to 23C, even if left on continuously. That said, 8 - 10 hours should be plenty for seedlings. (They need their sleep too)

BTW, are you in U.S. history gardening?

[Mark Rand]

I've got my grow lights on a 'smart plug' which I've set to be on from sunrise to sunset. To be fair though, that's topping up the overwintered chillies, not seedlings.

[Penellype]

Hmm, I set my growlights (LEDs) for 16 hours, having found that less tends to result in leggy seedlings. One of the videos I watched recently made the valid point that LED lights are not as intense as sunlight and therefore need to be left on longer than just during daylight hours.

It always annoys me that many sets of grow lights are sold with a timer which has a maximum of 12 hours on, 12 hours off. It isn't enough.

[mothhawk]

This might be of interest. It's the guy we saw in the video on seed depth - here he's testing light.

https://www.youtube.com/watch?v=YYjf4ncyARs

[Penellype]

This might be of interest. It's the guy we saw in the video on seed depth - here he's testing light.

https://www.youtube.com/watch?v=YYjf4ncyARs

Thanks Mothhawk - interesting that he comes out with exactly the same conclusion that I have done from years of experience - that 16hrs is about right.

[Mark Rand]

Hmm. I've now reset the growlight over the overwintering chillies to come on before sunrise, turn off later, then come on before sunset and turn off somewhat later, so the total illumination (sun + growlight) is about 16 hours per day.