Up until fairly recently all animal life was considered enemy to be destroyed or assimilated (as in mindless zombies controlled by plants) but lately Viridiplantae started to see benefits of cooperation. It mostly comes with enormous cost to ensure total control over the unwilling subjects and required significant portion of population to focus on maintaining that control. That of course was not without accidents when plants were rejected or animal in terror managed to overcome the control and went on the rampage. Especially considering that using mixture of telepathy, spores and biological "drugs" (produced by specialized plants) would often not be enough and then number of plants would have to grow into the subject. Important to note is that those plants would have to "root" into the animal forgoing the honor of stationary resting place. That would also significantly lower the Viridiplantae life span as they would die with their host compared to the centuries some of them could live provided they found good rooting place. Now if you consider a symbioses Viridiplantae so far achieved like with bees when they just let them collect they nectar and bees at their own will take care of feeding themselves, defending their nests (and Viridiplantae close by) and reproduction the effort required is impossible to compare. Viridiplantae may be set in their ways but they are not stupid. They cautiously tried to see if they could share similar symbiosis and gradually more animals were welcomed among Viridiplantae. Viridiplantae adapted by reducing number of new mind controlling plant being spawned and focused on those that could bear fruits or produce sweet nectar, and for those plants their primary function of sustaining their "allies" comes at no cost at all and required no effort. It allowed them to aid with research, teaching etc. That made the collective stronger so they changed. Now you could said they are ready too experiment with things larger and smarter that rodents so they are looking at minor factions ^^.
In the past I'd say Viridiplantae were very much like necrophages. Bound to destroy anything that wasn't them but now that they realized the benefits of cooperation they realized they needed to shift their focus to be more friendly and open to strangers. But as a faction that routinely sacrificed millions of them every year (and they still do but now it's only in hundreds of thousands) they are pragmatics and still retain their armies of mind controlled animals. And they know there will never be peace with necrophages (mostly because of the necrophages unwillingness to leave them alone). But deep down below pretty flowers and colorful vines they are not that different from necrophages they just try very hard not to be as this allows more of them to live and the more of them lives, the stronger Collective becomes.