Tape around the mortise and tenons, and fill the voids with a sanded grout mixture, adding pigment to match the bench color if desired. After the grout has cured, remove the tape and clean with a damp sponge.
Having the correct planting space is usually a problem when trying to plan your new garden layout. If you don’t have enough room to plant this year try going vertical. This DIY Garden Tower Planter (strawberry planter) will give you