My tree, planted accidentally in some compost, is now on it's 3rd year and
approaching 20ft high. I read some where that it has a 50-50 chance of
being sterile.

Any suggestions as to improving it's odds? Leave the Russian Playboy
discreetly on the porch? There are no other A trees around, but from what I
understand it's not necessary. Bees? I've pretty much stopped watering it
cause it is so tall.