Apps like Maps Made Easy will allow you to collect high resolution images that they processing can stitch into ortho maps as well as generating 3D info of the same area. Leaf growth is a tricky mission because it will be almost impossible to examine the same leave from one scan to the next. And mapping foliage is always tricky. With good data, especially if you can provide a surveyed ground control point, you may be able to make some determination about changes in the general height of the plants.