why didn't the fruit tree flower?

So yesterday I was doing a backyard consultation, and I got asked yet again "So why didn't my apple tree flower last year?"
(this isn't the first time I've heard the question. finally i decide to figure out the answer)

Sometimes good fruit yield years are followed by bad years.
Sometimes the tree just isn't healthy, or is in a bad place.
But what about a healthy looking tree that's in a pretty good spot, that has had good fruit set in previous years. Why why why?

In this particular site, the only changing factors were 1) more sunlight as a fir was cut down to the south, which you'd think the tree would be happy for 2) a compost pile started getting piled in its root zone. maybe all the nutrition went to the trees luscious leaves and it didn't thus feel like fruiting?

Any ideas?

many apple trees are cyclical..they will flower and bear only every other year..sometimes every 3 years..so don't be surprised or disappointed..

if it bore heavily last year it put a strain on the spurs..causing them to rest for a year..not uncommon at all..sometimes happens on other fruit trees too but apples are big for skipping a year.

you should have a great crop this year if you have the proper weather for apples.

I've also read that certain fruit trees (apples for sure) need so many frost-days to set flowers the following spring.  I don't know if this is your issue or not, but some with warmer weather do to the climate change are experiencing this.

Excess nitrogen can often trigger excess foliage growth at the expense of flowers. I have seen this time and again amongst all sorts of flowering plants... cut the ferts for a year, or at least the N.

HG

or maybe move the compost pile away from the foot of the tree

I don't see location information in your profile so I don't really know how to base my answer.

But yes, many apples tend to bear every other year so that could be an explanation.

The other obvious one for my location is, is that tree and appropriate variety for the number of chilling hours it is likely to get in your location.  Many types of fruit/nuts won't bear in my location unless they are specifically bread to be low chill varieties since we don't always get enough cold hours for the more temperate varieties.

Then I know up North, sometimes it can get warm suddenly too early in the spring, the fruit trees are tricked into breaking dormancy early and flowering, then a later freeze/frost will come along and kill all the flowers dashing the seasons hopes for fruit.

While this isn't directly applicable to an outright failure of apple trees to flower altogether, certain apple trees also have the issue that proper pollination requires the proximity of a different species apple tree !!! 

I have several dwarf Fuji apple trees ... interspersed with dwarf Goldrush apple trees ...

(snip)"I must emphasize that by no means do I suggest you should be growing apple trees of just one variety per season. Rather, you must plant two or more varieties that bloom the same time in each apple planting. Why? Well, don't forget "the birds and the bees." Yes, I'm talking about sex: pollination.

Most apples aren't keen on incest, requiring trees of a different apple variety for pollination (even with the exceptions, pollination is superior when it comes from another variety). Oh, by the way, apples don't look down their noses at crabapples, as if the latter somehow weren't "real" apples. No, apples are sometimes quite willing to be pollinated by their ornamental cousins. This fact obviously increases your leeway in terms of landscape design.

A couple of caveats, before leaving the issue of pollination:

•The pollen of some apple varieties is sterile, so don't rely on these as your pollinizers. Examples are Jonagold, Mutsu, Stayman and Winesap.
•The transfer of pollen from one apple blossom to another is largely the work of those busy little garden friends, the bees. So be careful not to apply insecticides during the blooming period -- or you'll lose your best means of pollination"(snip)

from http://landscaping.about.com/cs/fruittreesbushes/a/apple_trees_2.htm

Maybe late frost damage to flower buds... hard to think of a reason that would result in NO flowers...

Which is why I went to more chemically dependent solutions to this issue, Paul C...

Mel, not so much a matter of different species as simply a different individual. Some fruit trees can be self-fertile, but apples ain't that tree...still, flowers should be there to be pollinated or not pollinated as the case may be...

HG

I don't know whether or not this applies to your trees, but it does to my young trees -- if the branches are growing more vertically than horizontally, you may not get any fruit.  I have three young trees (an apple and two plums) that had to be caged when they were planted to keep the deer from immediately killing them.  We only had small cages on hand at that time, and it forced the young branches to mostly grow up (any that grew horizontally were eaten by the deer as soon as they stuck out of the cages).  So, even though the trees are now five years old, we haven't seen a single bloom on them.  This year I'm going to replace the narrow cages with much wider ones and do some work on the branches to make them grow more horizontally, so hopefully next year we'll get some fruit!

Kathleen