I would like to make a multi-tiered farm on my homeworld. Having layers of dirt with plants in between, my only problem is the vertical space plants take up is different. Having a need for a pattern/symmetry personally I would like to know what is the maximum space plants need and the minimum. Also if they could be grouped so I have categorys and such that would be great. I think the wiki says something about this but from my understanding you can go lower on some of the plants, even if the visual goes into the dirt.
Use several 4-block tall sections for most plants, and have the top tier or two a bit taller for the larger plants. Another method is extending every other platform and using that space exclusively for taller plants. This improves access and convenience at the cost of compactness.