Photoperiod Induced Dormancy, Is it Possible?

Hi everyone,

I’ve got some southern live oaks up in Chicago that will almost certainly die if they face the Chicago winter, so they are currently sitting in a grow tent indoors. Florida doesn’t have much of a winter to speak of, but it does get down into the low 50s/40s in Orlando where the trees are from. I worry that not exposing the trees to an extended period of colder temperatures will result in their eventual death from sugar exhaustion.

I’ve read the dormancy is induced through temperature and light. My grow tent lighting could easily be shortened to 10 hours or less a day, but unless I want to freeze my family, I am not sure how to get the temperature down to the 50s. My question is whether I can induce dormancy in the trees using a shortened photoperiod alone.



In the cannabis industry, the plants are heavily controlled by photoperiod.
During the vegetative stage, the lights are kept on for 18 hours and off for 6 hours for about 2 months, then changing the schedule to 12 on 12 off and the plant is tricked into the flowering stage.
So manipulating the photoperiod will definitely work.
As far as controlling the temps, possibly an A/C unit in the tent?
I know keeping the roots warm when the air is cold is not harmful.

Does the tree really need to achieve dormancy or is it just an assumption? If it survives in Orlando, I can’t imagine it really needs dormancy.

You’ve got to hand it to the cannabis crowd, they do know indoor growing. What I am not sure about is whether the photoperiod actually induces full dormancy in addition to vegetative and flowering stages. I believe vegetative and flowering stages are less temperature dependent than they are photoperiod dependent. That being said, it does seem to follow logically that it would have some effect.

I was thinking of doing <10 hours of light per day come December to see if that does the trick. So far I’ve been mirroring actual sunlight times and they seem to have slowed down since I took them inside at the beginning of September and got them under 12 hours of light.

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That is a very good point. My assumption that the trees need dormancy is based on the experiences of another guy I know who had a southern live oak die after 3 years of sitting out the winter in a heated greenhouse. Given the number of ways there are to kill a bonsai, it very well could have been some other factor.

If the trees make it through this winter I may do some experiments next year to test out whether they can just sit with the tropicals. That being said, if they die out in three years, that’s a steep price to pay for knowledge.

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Is a southern live oak a deciduous or broad leaf evergreen?I have asked a similar question about olive trees on the Q&A. Ryan explained that it might be necessary for conditions to be favorable for a light dormancy period. That being said, olives can meet their demise in temperatures lower than 40 degrees F. The potential problem with photo period induced dormancy is leggy unhealthy growth in broad leaf evergreens. so with my olives I seek balance in getting as much light to the trees as possible while keeping the temps at metabolic 42F. so far so good. I live in Nevada where the cold is not as bad as Chicago, but it can get down to 10F on occasion. There are a lot of variables to this post so I hope it is helpful in some way. Keep on truckin!

Southern live oak is the same genus as a Coastal live oak, which I believe are broad leaf evergreens. I had not considered the leggy growth factor, any idea on why that happens?

If a BLE doesn’t go into some sort of winter dormancy it continues to push growth. Just not very quality growth. Not enough light during the day, I imagine, and used up resources. I still have a lot of time to learn more, that’s for sure!

That makes sense. It sounds like I’m heading into uncharted territory here. I am going to have to collect data and get back to everyone with some findings. Thanks.