Very true Chris. Danil, from the photo the Wisteria leaves are probably the emersed form rather than submersed. This is likely due to having been propagated emersed, which nurseries will do with "bog" plants as it is less expensive and faster than submersed cultivation. Once planted submersed, the existing leaves will die off as new submersed growth appears [but see below]. I've no idea just how long this might take, but it would likely be influenced by conditions (light, nutrients).
The photo I am attaching shows a couple submersed plants that happen to have both leaf forms, though grown submersed. The leaf shape with this species is affected rather significantly by temperature and light. In brighter light and good nutrients, the finer pinnate leaf form occurs, while under less intense light the broader oval form. Lower temperature causes less pinnate and smaller leaves, while higher tend to more pinnate and larger leaves.
I would not do any trimming other than removing the dying leaves (none show in the photo) as they appear. New leaves, stems and roots will grow from each node along the stem; mainly new leaves and roots from every node, and branching from nodes where the stem is cut usually.
Byron.
