It is probably not worth the time and effort to apply for an import license. If you were a business and looking to import substantial numbers or on an ongoing basis, maybe, but I doubt an application from an individual will be seriously considered. If you are lucky, you might receive a quick denial otherwise the process will probably drag on like so many other processes here.
If these plants are already specifically excluded from importation, then there is your answer. There will be no exception granted. If not excluded, the onus would be on the applicant to show that the plants pose no detrimental impact to the environment and the ecosystem, today, next month and 100 years from now - that would require some serious supporting scientific data.
Generally individuals do not undertake this type of bureaucratic process. Find an indigenous floral option and save yourself the aggravation and the potential consequences of doing an end-run around the rules like the cockroach guy recently.