As of today (and until I decide it doesnt help) I'm changing the way I ship trees.
I have always put a cover layer of small stones on the soil surface, but now I'm going to provide the stones separately and ask that you wait 2-3 weeks before spreading them on the soil surface.
Because by exposing the soil surface, I think it will be easier to tell when the soil has dried out enough to need more water.
1- You'll be able to see the texture and colour of the soil surface
2- by shifting a little soil to the side you'll be able to see how deep into the pot you need to go before the soil appears darker
3- You won't have the stones acting as a barrier to retain moisture. Now this is both good and bad, but since I have found that more bonsai die by drowning, it makes sense to me. So by withholding on the stone cover for a few weeks you'll have a better idea how much water the tree is taking up (at that time- but its always changing).
Proper watering is hard. Trust me. I've been doing this for years and I still mess up from time to time. But as much as I hate to admit it, when I mess up its because I got careless and wasn't paying attention.
There is what used to be a lovely tiger bark sitting downstairs that dropped every one of its leaves because I repotted it and then let it dry out- that's called "yer bonsai double jeopardy".
Watching the soil is one hint on when to water.It changes colour, the texture is different and if you've really let it dry out you will see it pulling away from the sides of the pot.
Feeling the weight of the pot is another
Invest in a moisture meter- use it to verify your judgement of when to water.
A common measure is to feel the soil below the surface to determine if it's wet and I confess I've used that instruction many times, but to tell you the truth I personally can't feel "wet". I can feel hot and cold, hard and soft, but not wet. Try it! Stick you finger in a glass of water and ask yourself how does wet feel? Nadda- until you take your finger out of the glass and some water is still on it. So I'm thinking that as a way to tell if you need to water your plant- this is kinda useless. I'll be removing it from my instructions and looking for better help.
A better - but more difficult way to know when to water is to carefully study your tree.
Water your tree well and the next day look at the leaves and the new shoots. (And pick up the pot to feel the weight- Water is heavy)
The leaves should look firm, maybe even a little shiney and relatively bright. Look to see how prominent the veins are ( if there are any). Are the spread out like an open hand? Now look at them every single day. If you're paying enough attention you'll see the lose some of that gloss, get a bit duller. They'll look a little thinner and the veins will stand out. They'll start to curl in.
On deciduous trees you'll see the ends of the new shoots start to droop as they are one of the places on the tree that are the most sensitive to watering since the tissues are holding so much more water and haven't hardened off yet.
A closing point for this article - and a chance to conclusively demonstrate why I will never make a living as an artist- is the highly scientific illustration below.
Here's what its about:When adding water to any potted plant, gravity will pull the water down until a small - but consistent amount- is left in the bottom. The problem with bonsai pots is that - for example- an inch of water at the bottom of an 8 inch deep pot is one thing but in a 3 inch deep pot you still have that same inch of water in the bottom, which means that most roots will be sitting in it.