When does a puppy starts shedding?

At 12 months it should be hitting the floor but that does not mean its fully grown into a full coat the shih tzu will have its full think double coat at about 2-3 year depending on hair type. now the hair above the nose is a different story it will be able to going a rubber band at about 6-7 months but wont be fully grown out till around 1-2 years. i am currently growing out y shih tzu puppy now and have a ale eho is full grown he has a full think double coat which is hard to remove mats because there's only minimal grooming aloud on a show shih tzu as far as cutting the hair so all mats have to be brushed, conditioned out.