Starting my first grow and I am a little worried about them out growing the containers I have for them. I have very limited space and am going to put them into flowering about 2 weeks into veg because they are a mango strain and I have read that they will explode in size more than other strains when they go to flower. I have 2 three gallon pots for two of them and 2 two gallon pots for the other two. I am pretty sure that the two gallon pots will not be sufficient but will the three hold up fine? I only have 33 inches of vertical space so I am going to LST them.
You may want to consider the 2 gal since a good rule of thumb is 12" in height for every gallon. and you have to account for the height that taken up by your pot. That should put you around 30-36 inches.
Are they seed or clone? Seed take up more root space than clones. Either way, I think you'll be ok with 2-3 gallons indoors. I personally like smart pots and camo pots because they make you get a denser rootball and you can use a smaller pot and not get rootbound.
They are from seed and right now I have two 2 1/2 gallon pots, one 3 gallon pot, and one 1 1/2 gallon pot. Hoping to get 3 females out of 4 seeds and if I do and one female is in the smaller pot I will transplant her into one of the bigger ones. How do you transplant without breaking the stem?
I have always had great success with transplanting. I just kinda get a feel for it. I have heard people say to wait till bone dry and I have also heard some people water first. For me I guess it is usually at least a day after watering and usually a day before bone dry. The key is really getting a feel for how the root system has developed. Once the plant has outgrown the container the roots will have form a sort of compaction which will hold together well during transplant the majority of problems tend to arise out of transplanting to early.
Put one hand over the soil around the base of the plant and flip it upside down, catching the rootball as it slides out. You may have to give the container a little shake or poke the bottom of the rootball through the drainage wholes to push it out. Just don't grab the plants and try to pick it up by the stem. You'll rip the roots. If the plants are big, it helps to have two people. One can catch the rootball while one tips the container.
Does the whole thing just plop out in one big piece of soil or is it going to just crumble when I flip it over and end up in a mess on the floor? Anyway to prevent that?
It depends on how well developed your root system is. If you're talking about transplanting a young plant it will probably fall apart. I really don't even think you need to transplant. 2-3 gallons is plenty for small indoor plants. Even if they grow rapidly in flower, they still won't have long to develop roots. Once you flip to flower, they mostly focus on flowering, not root growth.