Headcanon partially/tentatively accepted, with some reservations. The main reservation is the notion that tiny plants such as this could ever sustain a civilization, especially a highly advanced, space-faring one that built enormous machines (more enormous even than themselves), and that mining Energon is a result of greed or consumerism. Energon mining goes back to before the cataclysm - in fact the original Predacons devoured Cybertronians who were full of delicious refined Energon from their good diet, until Prima defeated Predaking with Star Saber and won the people’s freedom from his predations. (He notably didn’t forbid the Predacons from eating Insecticons (who can refine even trace amounts of Energon from anything they eat now matter how crude), even the talking ones…). Those Cybertronians were referred to as “miners”.
I see the discovery (or more likely gift - Energon mining and refining were apparently taught by Alchemist Prime) of widespread Energon refining as more akin to the agricultural revolution on Earth. The domestication and cultivation of wheat, rice, and other staple crops allowed humans to move beyond small hunter/gatherer societies and establish settlements with larger populations. Settlements allowed the development of education, astronomy, time-keeping, writing, metalworking, architecture, mathematics, philosophy, trade, fine crafts, higher education, and all the other things we associate with civilization. Some of those things come with their share of problems, but they are all good things. And they are all things made possible by people having a ready supply, and even a surplus, of nutrition, so they can occupy their time with pursuits other than filling their bellies. It’s tempting for us to view large-scale mining as inherently destructive or greedy, but on Cybertron Energon is food, it’s in the ground, and “industrializing” the process of attaining it to some degree seems closer to the domestication of staple crops. Of course that can be overdone, but there is no indication that Cybertronians really over-mined Energon until the War. Primus’s own production, combined with the “Energon cycle” that breaks down old metal and dead creatures seem to have been able to keep up. (I think they augmented the Energon supply with fusion, wind, solar, and other forms of energy production for their cities, as some of these are mentioned in the novels.)
But anyway, that’s a tangent. “Plants” like these would be awesome on Cybertron, but probably always remain small and not widespread. I don’t think there would be forests - more like patches of flowers. They likely grow on or near Energon veins, and can give an indication of what other minerals are present. As they sip up Energon, they also extract the impurities, lending them various shapes and colors. Cybertronians consider them a variety of living crystal, the closest concept they have to plants. If you know which ones grow from which minerals, they can be used as spices, perhaps lending a more interesting flavor than the minerals on their own, and thus being more valuable and expensive. Imagine caves full of them, glowing faintly in all their colors because of the Energon inside them. Back when newly Sparked bots had to wander through the Underground tunnels, they might discover they could eat them. In old times, an Energon miner who knew their stuff could find good ore that way, and also might pick some plants to sell on the side to discerning cooks. The rise of more concentrated industry and then the castes would have forbidden the poor miners from reaping the benefits, and made the cultivation and sale of plants and plant-concentrated Energon something for a higher caste to take advantage of. Some plants may indeed have become endangered through over-harvesting (though their mineral nature and freedom the constraints of needing parents meant they would always regrow once conditions returned to normal) but the castes in charge of them would preserve them in order to preserve themselves. Artificial scarcity might even be a thing - a “rare” spice in the fanciest restaurants in Iacon might be the same ubiquitous “lichen” crust miners in Slaughter City scrape into their daily cubes of machine grade to make them palatable, and never saw as anything special. Perhaps miners still slipped a few of the best plants into their subspaces to sell on the black market.
I think the idea of them being natural Energon refineries for other creatures is interesting. Cybertron has one food in its whole ecosystem - Energon. What purpose would predation serve in such a world, where you can literally just pick up the very essence of your creator out of the ground and be sustained? None, except for large creatures like Predacons that are unable to get enough energy from raw Energon. They get refined Energon from the bodies of their prey, some of which gets it from nibbling these Energon-concentrating “plants”, or, if we’re talking about Insecticons, can extract even trace amounts of Energon from anything they eat, even raw metal and ore. So there is a type of food chain, mostly having to do with the concentration of Energon each type of food contains. If you can just refine and concentrate the Energon directly, you can in a sense remove yourself from that cycle and get things done. That’s also part of why I headcanon that the “normal” species of Cybertronian - the miners - view obligate predators as marred and monstrous. “Civilized” mecha take the Energon directly provided by Primus from his own body (Cybertron), and predation and devouring have a strong association with Unicron (perhaps predation only even entered their world because by the time the Well was activated, Unicron had already battled the Thirteen, and they had fallen into war among themselves, and those metaphysical wounds carried over). The knowledge and guidance of the Thirteen preserved them from having to debase themselves by killing in order to fill their tanks. I think they view “plants” as a type of crystal almost, only marginally alive and certainly not sentient (actually sentient, not sapient, which is people usually mean when they say sentient). It’s not the same kind of killing - it’s not predation. Ironically, I think they might actually view harvesting living crystals as being greedier and more questionable than simply mining Energon, giving the philosophical implications. It would be very luxurious to eat them I think. They’d be “extra” while refined Energon would be “normal”.