How are you creating the patch? Is it only one patch?
If you want the patches to be painted, you will need to create two patches: one for the island and one for the mainland.
Otherwise, you can create only one patch by introducing NaNs. For example:
V=[0,0;1,0;0,1;1,1;2,1;1,2;NaN,NaN];
patch('Vertices',V,'Faces',[1,2,3,1,7,4,5,6,4,7]);
That code creates two triangles without any connection between them.
