I usually post this every year to notify people who buy annuals like Impatiens or even Petunia's to carefully look at the plants and the size of the foliage. If it looks smaller than it should look, this is not just because it is a young plant. It means the production schedule in the greenhouse made it necessary to use growth regulators or inhibitors. This is a class of chemicals which can, and often does stunt the growth of the plant indefinitely. Many annuals will come out of it, but if the plant is too far along in the six pack or 4" pot, and if these inhibitors are used the plant is stunted in a more mature point in that plants life...mature for shelf at market, that is.
So, be aware and don't buy this type of plant even if it had a million buds. It will have those buds as a response to dying or stress to reproduce.