I have a small yucca plant (1ft high). I believe I overwatered it and the trunk went spongy and now feels like it's totally empty inside when I squeeze it, as if the entire inside rotted away to nothing.
Should I transplant the growing leaves which are on a small yellow attachment? The yucca was sold with three trunks with the smaller two having flat tops and the leaves are on the side at the top.
I'm not certain that's a Yucca, looks more like Dracaena fragrans, especially if this is a houseplant. It also looks as if the live shoot is trying to produce its own roots, so yes, take it off the main stem, right up against the cane, or even take the top part of the woody cane with that attached IF the top of the cane isn't soggy. If you take the top of the cane as well, and it looks blackened or not healthy inside, then remove the side shoot with a very sharp knife, cutting against the cane to get it off as intact as possible.
Put it in a small pot with drainage holes in some fresh potting soil; if you're using just the shoot, and those are small roots I can see, bury the bottom half of the stem in the soil. Keep it somewhere out of direct sun but with reasonable daylight. Water well initially, allowing excess water to drain away freely, then only water when the surface of the soil feels dry to the touch, but not so dry its shrunken from the sides of the pot. Allow excess water to drain out freely, then replace in whatever outer pot or tray you're using so the plant is not left sitting in water. Then watch and wait - it might work, or it might not...
Also cut out at the base the entire soggy cane in hopes it doesn't spread to the other cane in the pot, if it hasn't already.
