When do autoflowers stop growing? (first grow)

Hey brother well I'm my experience. They all stopped growing no later than week 5. And even in the last 2 weeks it'll only be a couple cm in the first 21 days or so of pre flower some autos will put on the same size they vegged out at. Some will only do 3/4. My advice look through a few diaries and see what you wanna grow. Must autos will have a guideline for height and 90% of the time they don't go over that. But again it depends on your environment if you can keep a steady temp through the light and dark window during veg there won't be a massive stretch. And you can also top and supercrop, LST and tie your down from the start on her side and LST the crap outta her to shape her to your needs Good luck pal.

Autos will often do some good stretching when they go into flower - but there's no definitive answer to you question.... each strain is different and sometimes there are differences between seeds of the same strain from the same seed bank. It's one of the irritating but challenging aspects of autoflowers - and there are a lot of growers who won't touch them because of this. Personally, autoflowers are all I grow and I love them... I love the challenge they present and the learning they offer. How long they will take until harvest is again something that is strain-dependent... I've harvested some in about 65 days from seed and others have taken twice as long. If you're talking about height, I've grown some that only got to 21" and another that was probably over 50" (couldn't really tell because I had to keep LSTing the hell out of that one to keep it in the tent!). Autoflowers are fun - embrace the challenge - and have fun learning! Good luck!

They will stretch again quite a bit in the first 3 Weeks of flower then slow down and produce some buds.