I know that some plants, like brassicas and tomatoes, can be potted up or planted out deeper than they were in their original containers. Is there a way to tell, in general, which plants can be treated in this manner and which ones must be planted at the same soil level?
Another one is clematis. Like tomato plants, these tend to be viney. Grafted tree peonies can and should be planted deep, so the tree peony will get its own roots going and become independent of the herbaceous peony rootstock. The same can be done with grafted trees, where likewise the rootstock was used merely for propagation and is not imparting some desired characteristics like dwarfness or nematode resistance that would be lost if the scion took root. These should not be buried at planting, however, but rather planted a little deep with the intent that soil will gradually wash in over the graft union and slowly bury it.
In general, it can be done with plants that are adapted to floodplain conditions where they naturally receive deposits of mud and silt over the roots during floods.
