I have two open bottom planter boxes from last year that are 10’x2’x2’. They’re filled with 50/50 topsoil compost mix which my local bulk supply place swore would work great. Well my peppers eggplant and beans were relatively happy. Okra and tomatoes were not. I had my doubts that the soil was too heavy and didn’t drain quickly enough. Fast forward to today - the soil settled about 6” below the top and I have a chance to amend w something lighter and fast draining. I’m looking at 3/8” lava rock or #3 perlite which is 1/2”. Leaning towards the lava rock bc it’s cheaper and breaks down more slowly. I’m also planning to add alot of worm castings as I have a bulk source.

I also have a closed bottom box (with some holes and gaps for drainage) that’s about 33” cubed. I stupidly filled it with the same 50/50 mix before remembering about the drainage problem. I watered it in after filling and the mix turned to mud at least in top. I’m now wondering if I should empty it out completely and fill it with a much lighter weight mix that has bark and lava rock added to compost and topsoil. Or whether it would just be better to empty it out partway and simply mix lava rock and/or perlite. I also plan to add alot of worm castings to this mix. Would love your thoughts. I have a lot of experience growing food in the ground but not in boxes.