Immersive Engineering comes with industrial hemp. If you harvest the upper part of this 2 block high hemp, it drops hemp fibre and sometimes seeds (configurable). After harvesting it will grow up the upper block again.
Seed have several grow states until they reach the 2 block heighth. So it takes some time until you can harvest for the first time. But after that, the upper block will reappear more frequently.

Maybe this could be an approach for large fern (or a future TVO jute plant) too.
It would integrate with Natura and IE that way seamlessly. It would streamline the harvesting experience.

Harvest the lower block would drop the seed only if it's not fully grown. Fully grown it will drop the crop and a seed but you have to plant it again.

As you use the minecraft vanilla fern, it might be impossible to do so. If this is the case, plz close.