That's one way to do it, sure. Just keep an eye on the runoff pH out of the containers so you don't get it too high by accident! You probably won't need to do the higher pH waterings for a little while anyway.
I actually think that adding calmag to your watering solution is preferable. Then you won't have to fret over pH.
stinkyattic Reviewed by stinkyattic on . outdoor in containers, I think I heard I need calcium? It feels quite foolish to be asking this question. My first time growing in containers outdoors. I searched all over google and searched the forums. I know I need to supplement calcium because of acidic rain and such. My tap water has a pH in the high sevens, close to 8, perhaps this is due to calcium content? Would it be enough to water plants with tap water once a week or so? Using buckets ranging 2-5 gallons (planting late in season) I do not think I have access to calcium Rating: 5