This aroid comes from tropical Central and South American rainforest conditions, where roots grow in loose leaf litter and airy organic material rather than dense ground. That background helps explain why Philodendron 'Ring of Fire' prefers soil that stays lightly moist but drains well.
Its roots benefit from oxygen around them, so the best soil for Philodendron has a loamy, peat-influenced texture with plenty of organic matter. This kind of substrate holds enough moisture for steady uptake, while its open structure reduces compaction and supports healthy root growth.