We have 8 biennial apples that all bear on the same year and then have no fruit on alternate years.
I would very much like to change about half of the trees to bear in the alternate year.
Can I do this by thinning all the blooms/apple-lets off of a tree on it's "on" year to encourage it to bear instead on the "off" year? (sort of "re-set" the clock for the tree?).
Thank you in advance for anything you can add to help with this!
Hi Avella, welcome 
- and great question. Most people, commercial orchardists included, do not want the heavy bearing at all … fruit are small, limbs break, inconsistent ripening, disease spreads… So what you’d likely want (short of more varieties) is to regulate their bearing.
I’ve dealt with a massive full-sized Gravenstein apple tree that’s a bigtime biennial bearror, too. I’ve not gotten into snipping blossoms … and forget the details.. but heavy thinning fairly early in apple development seems to reset their hormonal balance and regulate bearing. Not that I get this accomplished every year… but it has worked over the 3 decades I’ve tended this tree.
Hopefully someone can give you more details as to the biological facts and the best timeframe for thinning, but I recommend you go for balance in overall production as opposed to ‘alternate bearing’ of individual trees.
As Ted Swensen used to say, in a heavy bearing year, wipe out the fruitlets within 30 days of peak bloom. In a light bearing year, prune.
John S
PDX OR