I actually have a customer that I work with that does just this. She uses the Sumo Cakes on her houseplants. She places a few cakes in a gallon jug. Shakes the jug and lets them dissolve. Then waters like she normally does.
And how often she repeats it, do you know? Maybe it depends also on the bonsai and size and in how much water she dissolves it also[/QUOTE]
She said she does this once a month. Every other time she waters. But remember these are houseplants in potting soil and not bonsai in bonsai soil.