reset the picktreeitem

[saltwater]

I have picktreeitem that changes parameters in the source when another picktreeitem is selected. I've done this using

datasource.setDefaultParams(new HashMap(){{
	if(parentId != null) {
		put("default.parent.id", parentId);
	}
}});

where datasource is set using

setDatasource or setOptionDataSource

The problem I've found is that the tree is cached, so the first time through it properly sets the parameter and retrieves the appropriate tree. The second time through it also appropriately sets the parameter, but doesn't refresh the root of the tree. I've tried

invalidateDisplayValueCache()
and
DynamicForm.resetValues()

but this doesn't seem to affect the tree. Is there anything I can do short of destroying and recreating the tree.