Just how large can I grow this OG Kush Autoflower ...

Hey there so your size doesn't look bad for three weeks. The only thing I see that might help things is to lower the night time temperature, the 80s are pretty high unless you're using a co2 product. Like other mentioned you can try playing with the light to stretch it, but i think its height will improve over the next 4 weeks. When i was curious about the possible size i checked a few other peoples same strain diaries and see where they were landing around..that might help give you an idea of the end results. ✌️

hello grower, relax is normal, just keep in mind not to put too much water and not drown, if you go through my profile you can see my northern light, was the same in the third week and then in the 4th and 5th has given a tremendous estiron , must be creating roots, greetings

She should hit flowering stretch in the next couple weeks if it is an autoflower. Some can grow up around 3 to 5 ft tall with a lot of light. The strain you listed growing is not an autoflower though. Good luck with your grow!