After you harvest a plant, can you just put it right back into flowering or do you have to revegetate?

You most likely need to reveg it unless it has alot of leafy green growth on it still..some people multi harvest some strains like "Flo" over a period of time but in most cases it goes - veg flower, reveg, flower

In order to reveg successfully I would transplant the plant if in soil to a new bigger container and give it some Nitrogen rich veg fertilizer and 24 hours of light. The plant may very well be stunted at first and not know what to do and the first new growth will be possibly mutated and wierd. It may even grow male flowers because of the stress. Just pick those off if it does and don't let them open up. Once the plant has grown sufficient new vegetative shoots and leaves then you can reflower it again but expect a lower yield the second time around. Another thing you could do is reveg it and then take clones and grow them out. Hope this helps!

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Any advice I provide is only to be used by legal medical cannabis growers not acting in conflict with their respective state laws.

Thanks for the fast response, I mainly asked that question because I'm nervous about how much the energy usage will be with the light setup I want to use in my growroom. How large can clones be when you take them from the mother? I'm just looking for a way to keep the energy usage as low as possible.

Well the plant should not be in flowering when clones are taken as the flowering hormones intefere with the rooting process and they take very long to root, sometimes 3 weeks + and sometimes never.

You can take clones that are as small as 1 inch or big as 12" it really depends on how good of a cloner you are. They need to have at least one node between the top growth shoot and the space on the stem you are trying to grow roots from. You don't want the bottom of the clone to be a hollow stem with no node on it. The best clones size for clones are small with 2 growth nodes and the leaf tips cut off to aid in rooting and prevent water loss. Also obviously use a high quality rooting hormone like olivias cloning gel or technaflora root tech gel. Advanced nutrients also has a new one out called juicy roots that is supposed to be fantastic. Keep them covered for the first few days minimum but make sure to blow fresh air in at least once a day to exhaust old gases out and replenish the co2 they need for growth. After they are perking up more and it's been about 5 -7 days you can start to uncover them and give them more light just make sure the humidity stays high and do not overwater them or they won't have a reason to grow roots. Give clones light high in blue to aid in rooting. Flouro tubes, CFL bulbs in 5500-6500k, or Blue LED works great for this. Good luck!

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Any advice I provide is only to be used by legal medical cannabis growers not acting in conflict with their respective state laws.