I have two stone bookends I want to use to do a ficus over a structure planting. See the pictures. I want to use them back to back with a gap between as in the second picture. I anticipate there will be trunks and roots in the gap and I will thread roots through the carvings on the fronts.
But if I don't connect them in some way, over time the trunks and roots in the gap will force them apart and destroy the planting. I thought about letting that happen and ending up with a 'decayed' structure look but the stones themselves will always look undecayed so that won't work. If I am lucky in time the trunks and roots will fill the gap so it will won't be seen.
Any suggestions on how to permanently connect them 1/4 to 1/2 inch apart without it being visible?