PAR value and photoperiod at different stages?

What is the rule of thumb for PAR value and the number of hours of LED per day (photoperiod):

  • first month
  • veg
  • flowering?

Thank you.

@solarslurpie typically 18 on 6 off. When their ready to flip to flower 12 on 12 off.
Others have found various methods to use but these are the most common :blush:


Thank you very much. Do you know what PAR level? I find working with PAR numbers makes it easiest for me to adjust the height of the LEDs. I’m assuming there are different PAR values for: 1) first month 2) veg 3) flowering.

(alternatively, if we assume a 18 hour on, the Daily Light Inteval is interesting…I can use this value to backward calculate the PAR value).

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@solarslurpie no I don’t know the PAR. My lights are LED 350 W . I adjust distance between light & plant based on plant performance. I start with 12" if leaves look good I maintain it. Adjust accordingly to plants reaction is how I do it.

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Thank you. I very much appreciate your advice. It make a lot of sense!

Most recommend 300-500 umol/s for veg, 700-1000 for flowering. Most will tell you not to go over 1000 with out supplemental CO2.

The optimum efficiency for canna is 500+. It loves light. It’s a field crop.

Outdoor on a clear day you’re looking at 2000+, overcast it’s still over 1300. Of course there’s unlimited CO2.

Daily Light Integral. :nerd_face: The sum total photons per day - the area under the curve (in calculus that’s integration).

But yes, and if you think about it, you certainly don’t want a lower DLI in flower. That’s why I ran my girls hard. Im about 1500 at some of the flower sites. I didn’t want to drop below 700, so I just sorta kept an eye on em and let them tell me if it was too much.

But Ive got really good airflow in my tent (intake + exhaust fans) and they’re in my basement with all the pilot lights and stuff. I haven’t actually measured to know if CO2 above ambient, but I think it is.

If you really want to nerd out on canna sciences stuff make sure to look for Dr Bruce Bugbee. You can probably follow the rabbit hole from there.

Seedling 200-500 ppfd 18/6
Veg 500-700 ppfd 18/6
Flower 700-900 ppfd 12/12

These are the optimal values without the use of c02.

You can flower with less ppfd if your light isn’t capable of 700 or more but you won’t yield as much.

I’ve successfully flowered with 600 ppfd and had a decent harvest but that extra light really helps.

I also have a post here with the optimal dli values I will share too.