When to transplant/soil question?

Looking to find out when plants should be put in their final home/pots. Currently at 3 weeks and looking healthy yet a little small. They are in standard size solo drinking cups. I want to make sure they are strong and that the root mass is developed enough to hold the dirt together upon transplant. However I don't want to wait too long and have the plants growth stunted becuase they stayed within small cups for too long, and became rootbound. If I had only put them in the yellow solo transparent cups! Anyway here is a pic for you to judge size. I am going into week 4 now.
Also should I try to keep the soil mix in the larger pots, the same as the plants have in their seedling cups? I used 75 pecent top soil, 15 percent perlite, and 10 percent sand for drainage originally. Someone here told me I want to go a little heavier on the perlite. I am also considering other things to mix in the final transplant soil. Worm castings or any other suggestions are helpful. Your thoughts?

anyone????????

i've tried transplanting out of the solo cups & my plants died about 2 days later. You have to be very careful transplanting. I saw a posting on the how to grow mj post under newbie central and theirs looked to be atleast 7 weeks at the time of transplant. I am now potting directly from germination into the large pot that way my plant will be set. no need to shock or tear the roots.

I see so I must wait at least 3 more weeks. I'll try at maybe seven weeks. And next time I'll try your tip and just grow them in 3 to 5 gal pots. Why even transplant if you dont have to?! I guess I am going to have to wait until the plant looks about twice as big. Then I'll know the root system is more established. I am going to gently cut the sides of the cup with a razor. And carefully transplant in a pot with the soil in a spot that has dirt removed the same size as the cup. I want to keep the entire cups contents intact as possible.

TooSides said:

i've tried transplanting out of the solo cups & my plants died about 2 days later. You have to be very careful transplanting. I saw a posting on the how to grow mj post under newbie central and theirs looked to be atleast 7 weeks at the time of transplant. I am now potting directly from germination into the large pot that way my plant will be set. no need to shock or tear the roots.

Click to expand...

I have preached the from popped bean directly into the largest sized pot that will be used for that plant theory or system for years and most people think I am insane but it has always worked great for me.

To me it is easier, it takes less effort, you eliminate all the risk factor of handling your plants while repotting, you greatly reduce the chances of stressing your plants, you get better growth, as in more constant and even instead of in spurts when the plant can grow again because the roots can provide what is needed and then slowdowns other times. Unless you are still using pots that are to small you eliminate about 5 or 6 common problems that go with root-bound plants.
　
It only makes sense to do it that way.

They are big enough now. Don't wait 3 more weeks. Put the plant between your fingers and flip it over. You may have to crush the bottom of the cup a little because the roots wrap the bottom groove and hold on. If some of the root mass breaks a little it'll still be ok. Just be carefull and you'll be fine...

Thanks. I think I'll wait till the weeks end early next week just to be safe. I'll be at a full 4 weeks then. Thanks for your tips. This will be my last transplant!