Avocado flowering

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.
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