Sounds like a pollination problem I would plant another variety like gala or a horse apple to pollinate the 5 in 1. also do you have a healthy bee population if you spray a lot and have a lot of insecticides in use you may be hurting your pollination

Usually, with a 5-1 tree, pollination isn't a problem... because you have all those varieties on the tree. (Actually, that's 1/2 the point of a 5-1) Usually varieities are picked that will bloom around the same time and take care of all the pollination needs. Question... are the 4 other varieties' branches very small and the rest of the tree very large? Do you get much of a bloom? Do the branches of the other varieties bloom at approximately the same size as the rest of the tree? Do you have a crab apple or any other apple tree near by which could also be helping? Do you know what the vareities are? Hopefully others will have an idea. -Glenn

alan8, sometimes the growing base tree to which the 4 varieties are grafted to dominates the four grafted on varieties. The grafted ones disappear through shading or just didn't take to begin with. Your Apple tree is now probably close to blooming. Get some blooming crab apple cuttings in a bucket of water by the blooming Apple tree. See if cross pollination will set some more apples. Hope there is a bee keeper within a mile or two.

Cut out the fertilizer - unless your soil test indicates it's needed, you're probably keeping your tree in a vigorous 'vegetative' state - it 'feels no need' to reproduce, 'cause it's getting plenty of nutrients.
Are the varieties that were grafted on this multi-variety specimen appropriate for your climate? Depending on where in LA you are, high-chill varieties might not get enough chill-hours to bloom and fruit well.

Pollenization is rarely a problem in most urban/suburban areas east of the Mississippi - there are so many ornamental crabs in the landscape that there is rarely a lack of pollen. Now, pollenation...that can be a different matter - if you don't have honeybees, orchard mason bees, or another suitable pollenator to carry the pollen from tree to tree - it doesn't matter how much pollen is available.

Alan:

There is something fundamentally wrong about a 5-in-1 apple tree that has reached 25 feet tall. Can you recall how many years it has taken to reach this size, and perhaps the original source of the tree?

Multigrafted trees are normally sold on dwarfing or semi-dwarfing rootstocks, and would never be expected to become this large. If the tree came from a dubious nursery source, you may have something quite different from a grafted 5-in-1 tree -- something like a tree on a seedling rootstock, or perhaps not a grafted tree at all.

You have not yet told us whether or how much the tree blossoms in the spring. If a tree blossoms freely but does not set fruit, pollination problems may be suspected, but if the blossoms are sparse to nonexistent the tree sounds more like a seedling -- especially given the quality of the few apples as you describe them. You may have been snookered. Also, please tell us where you live in zone 8.

Don Yellman, Great Falls, VA

Sorry Alan, you already told us where you live and I overlooked it. The only other comment I would make is hold the fertilizer, unless you want the tree to become even larger. Most of us who grow apples try to keep the fruit within range of spraying, thinning, and picking. I guess there is always the outside chance that your tree will suddenly begin to produce wonderful apples.

Don Yellman, Great Falls, VA