I'd use triplesuperphosphate instead. Also incorporate it in the mix rather than top dressing. I also add rock phosphate. The two will together lasts for a few years and eliminates the need of annual topdressing.

Gerald

Gerald--here in the states it's called super triple phosphate ;-) My guess is that it's the same thing. I agree that it should be put in @ time of re-pot so the roots can use it right away. I got in the habit of using it having seen Roger Cook on "This Old House" toss in a handfull to insure a successful transplant job. I wouldn't recommend a handful for a bonsai pot, however.

Well, here in Enlgand we have superphosphate, an old favopurite of veggie gardeners. Im kinda limited to what i can get not having a garden centre for miles around but luckily our DIY store sells stuff that i need.

I'm sure it will do just as well as the stuff with the fancy name, and certainly better than not using it at all.