Large flora genera have a size limit of 20 meters, which is not even close to the maximum size for a tree, so to make bigger stuff people have to make individual species. I don't think individual species submissions are likely to be hurt by this. That said, I think that primarily submitting plants and insect-analogues that are not biome-specialized as regional genus groups is probably the best for Sagan 4 long-term because they can withstand periods of inactivity from the comparatively tiny number of people who are actually interested in making them.
My thoughts on genus groups are difficult to explain briefly. They serve a very important purpose in Sagan 4 both from a game perspective and from a realism perspective. For some strange reason, the types of organisms that people are the least interested in submitting just happen to also be the types that are the most specious on Earth, so limiting them to single species submissions not only potentially harms Sagan 4 game-wise but is also unrealistic. These fundamental organisms end up being absent from where they need to be and become vulnerable to sudden, ecosystem-devastating extinction, which ruins the fun for everyone. Plant groups that should be successful peter out from lack of interest and both wingworms and scuttlecrabs almost entirely went extinct from habitat loss.
Though the genus system originally served just to fill in pioneer species, once I joined the project and as I started experimenting with them, I slowly realized their potential to resolve the above problems and represent realistic specious genera. In case you haven't noticed, the culture surrounding genus groups has completely changed. Tons of overly-broad groups have gotten broken up, new overly-broad groups are being discouraged and rejected, and the genus system itself has been completely redesigned to encourage regional groups. This has largely been the result of my own pushing, and it has completely transformed the system from a restrictive mess that somehow allows "these are all the bees everywhere in the world with every diet a bee can have" to something better resembling single-species submission in nearly every way. This is because that is exactly what a specious genus on Earth typically is--it's a cohesive group of organisms with defined biology and behavior that are generally found in a broad region and simply speciate too fast to be feasibly represented species-by-species. You yourself have also had a hand in this change, as we also legitimized a habit of yours--elaborating on a specific species in a genus group as part of another submission--as something actually noted in the rules as a thing submitters can do.
I don't think ferries will be a problem for future tree submissions, apart from there probably being no redundant "x species in Y new location" splits. They aren't, and don't pretend to be, all sun-loving trees and shrubs of their size and habitat range, nor are they all the ferines. They are, specifically, all generic ferries, which are a type of fast-growing sun-loving woody flowering plant with berries and a frond-like leaf structure--and if someone wants something that is not a ferry, they can, should, and have to make it.
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As for the other comments...
Leaf shapes would be variants of the frond. I ran out of room and decided it wasn't important enough to have more than just a textual elaboration, since it wouldn't vary a whole lot between species.
The flower colors are just flavor at the moment because we don't have enough pollinators for specialization to exist yet.
I'm not sure how to elaborate on flavor. I based it on how some Wikipedia articles I looked at describe the range of fruit flavor in a genus.
I feel like a shade-tolerant ferry would be better for a descendant that keeps the same genus, since that's not standard for the genus group.