I have some thoughts on this:
- The statistical distribution of growth cycles will be tightest in species (if grown identically), but the more complex the hybrid, the broader will be the distribution.
- Plants are individuals, too. In a population of "X" number of the same plant, all grown together, you will see variations in growth cycles.
- You're right that culture will play a huge role in defining a cycle. If you and I grew the same plant under identical conditions, except mine was in lower light than yours, you might see a couple of bloom periods - let's call that the end of a cycle - a year, while I might only see one.