When it rains my planters flood and water leaks into house on concrete slab and wall. How to seal joint at foundation

Better solution is to start getting the water away from the house. Do you have gutters? Collecting the water and moving it 4/6 ft. away from the house may solve the.problem. Very hard to seal the wall/ slab joint when house is already built.

The first thing I'd do is punch a few holes in the base of the planter to drain out on the ground. If there was still a problem with standing water I'd consider add ing either a french drain or digging in a dry well. (see images) Good luck, Tom