I've grown mine out several times over my lifetime. When hair is short it often tends to grow upward and outward, which can look kind of messy when grown out. It sometimes takes a several months or a year for the growth direction to change because of the weight of the longer hair, but it does eventually.
You just have to tame it as well as possible during this time and know it's not going to look perfect. If you're lucky, you can do this with hair products, but I've used headbands, barrettes, and even hats to keep it flat while growing it out. Once it gets long enough, though, it looks fine.
~ Lyric ~