There are so many factors at play in a diverse ecosystem. For one, the plants compete on many levels that it becomes too "chaotic" for an immediately discernible overall synchrony to arise. Even then there will likely be a number of symbiotic relationships between different species that depend on the presence of varying flowering/life cycles. The bamboos come out all "well behaving" and synchronized perhaps only because the natural evolutionary process is trying out everything everywhere and something somewhere will be judged to be synchronized with distinction.