The best way to get the largest leaves on your Philodendron melanochrysum is to provide it with the best care possible. It is extremely important that you attempt to replicate their natural habitat as closely as possible to make your plants are comfortable enough to grow enormous leaves. Maintaining warm temperatures & high humidity, regular repotting, and giving it the correct soil are all basic stepping stones you can take towards helping your Philodendron melanochrysum develop big leaves.