Mystery plant

I have these great plants growing wild all over my garden. I think that they’re great, but my housemate is concerned that they’re not indigenous. They look to me to be part of the philodendron family? Does anyone know what these plants are, and if they’re not indigenous, whether or not they’re ‘bad’ plants; e.g. do they take water from other plants?

Check out the studs that form at the base of the plant when a new leaf is growing. Fantastic!

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