root sizes

Im go be veging 10 unfeminized seeds. I know that I cant tell the sex untill after i put them in flowerng stage (right?) and im hoping that my end females (hopefully less than 5) will all end up in 5 gallon buckets. I do NOT have room for 10 five gallon buckets in my grow room. How big is the root system at the point which their sex shows? whats the smallest size pot or container i can get away with growing all 10 in before weeding out males and transplanting females?

on the same note, Im going to be pairing a female and male in another room to harvest some seeds. Are the conditions these 2 plants (which wont be smoked) are raised in affect the quality of the seeds? (germ rate / future thc content)

you can grow a plant in a shot glass if you want

Id have to assume it wouldnt be good to let the roots get that tangled tho? Im planning on veging to 16 inches...

do lots of reading- search preflowers.
you can also take a clone off each plant &put the clone in 12/12 lighting to determine sex.

Many plants will sprout preflowers after a month or two of veg, if so you can sex before flowering.

If you end up with too many females, pick the best ones that you have space for. Just because you sprout it doesn't mean you have to finish it, and it's not uncommon in gardening to plant more than you need and thin out the worst looking ones.

The size of the root system is going to be determined by a large number of variables, none of which is whether they are in flower or not (though I suspect what you really mean is after a certain period of time...). It's not advised to sprout more than one seed per pot however because thinning and transplanting when the root systems are mixed is a pain and quite error prone (meaning you will likely damage them). Single plants can be transplanted with no stress for the experienced, and minimal stress for even the novice if you follow some simple steps you can find all over the web. Far as transplanting, I start in very small peat pots, transplant to 1gal then 2 gal nursery pots, then 5 gallon buckets which are drilled with 1/4" drain holes. With smaller plants I have found that watering is much easier to get right in smaller pots, and it allows me to maximize space.
As far as the roots go, it really is more proportional to the plant size than other factors (at least in my experience). You can raise and flower a plant in a 1 liter pot, or even a dixie cup (the shot glass competition showed that you can sorta do it, but there really is a minimum size you can expect out of a plant ), but compared to something in a 5 gallon, those smaller pots will have much smaller maximum plant sizes they will support. If you have space for 5 gallons, then they will grow to that space, and you will just find that the plant will slow down growth dramatically when they run out of space. After some time you will get a very good idea of how large you want stuff, and you can tailor your veg time to growing plants to your flowering space. If you can't seem to get the plants big enough, then pot size is one of the first things you'd check.

Thats good to know then, Im growing white widow and I only plan on veging for 2-4 weeks. I would LIKE to super crop but i may just not have that option this grow as i dont have alot of space. I think im going to use this grow to get kinks worked out, the next grow to get some feminized seeds, and the third grow (come summer when i have more time to spend with the plants) I will get into super cropping and some more advanced techniques.

thanks for your response. I think im going to use gallon jugs for vegging, then after i find their sex ill transplant 3 females into my 5 gallon buckets. My last question would be this: Im planning on removing a male and a female to let them seed (in another room). Do i need to set up another grow room for them? seeing as i dont care about thc or quality, I just want seeds, will un-ideal conditions compromise the quality of the seeds?