I have bought this Japanese Holly Bonsai yesterday from a local garden centre. The pot is 20cm deep, 12cm wide and 35cm long. It has no drainage hole at the bottom. The shop told me that it doesn't need drainage hole as it has stones at the bottom and moss on the surface covering the soil, just keep the soil moist and it will be fine.
Can anyone give me some advice or your thoughts?
Thanks.
I would not go back there.
If the tree's roots sit in water they will suffocate and die, then the tree will die, or at very least have poor health.
If the water has calcium or anything else, then when you pour water in you pour more calcium in. The water evaporates leaving more and more calcium. Eventually the tree has more calcium than it can handle, and has poor health.
Poor health means it gets weaker, weaker, and dies.