So I'm finally succeeding rooting ivy on water, I don't want to ruin it when placing them on the soil. Anyone knows how long should I wait? I know that for pothos I should wait until the roots are around 2 inches long.
Should be fine if the roots are an inch or more long - Hedera is a tough plant, but plant up into a small pot with new potting soil to give it time to develop properly before planting in the garden (if that's your intention). If tou want to keep it in a pot, pot up into something larger as it grows bigger and has formed a good root ball.