is there some reason you have ruled out stem roots ...

the roots that anchor ivy to vertical surfaces???

see link

ken

Here is a link that might be useful: link

Welcome to the Garden Web! Please don't let ken's curt response push you away. We see questions about aerial (called adventitious) roots very frequently.

Many different kinds of plants develop adventitious roots; they are perfectly normal. Hedera helix will utilize them to climb up a surface. Those little rootlets will insinuate themselves into the tiniest cracks and crevasses of trees, fences, walls, etc.

Be careful where you allow a Hedera to grow. Those little aerial roots can cause damage.

I used to panic about those too and tear them off whenever found. Grown indoors I don't think these roots do much. Grown outdoors those would likely develop further and start attaching the plant to whatever surface it is climbing.