Unless your neighbors grow apples as well, you're going to need at least two different apple trees (for cross pollination) or a single combo tree with multiple types grafted on. Unfortunately, you seldom have a choice of what the various types on a combo fruit tree will be. WSU has done a great deal of study and trialing of various fruit varieties best suited to the Puget Sound region and those offering the most disease resistance. You might want to peruse their website to get a listing of those apple varieties that they recommend and compare to what your local nurseries are offering.

One thing about the combo fruit trees is that they often experience graft failure - one or more of the grafted types will die off, leaving your 4-way combo as only a 3- or 2-way :-((

Here is a link that might be useful: WSU apple tree trials

At the site that Pam mentioned, there is a new, downloadable bulliten, Fruit Trees for Western Washington. It has some good recommendations. If your space is very limited, consider buying trees on a very dwarf rootstock, such as M-27, P-22, or M-9. That way you could put 2 trees very close together and solve the pollination issue.

We chose a Liberty apple tree at LeCoteau outside Victoria at their reccomendation for disease resistance and good eating and cooking apple. We have been pleased with it and seen it recommended elsewhere as being most resistant to scab etc. Consulting with a local nursery that specializes in fruit trees may be helpful.

Here is a link that might be useful: le coteau

Liberty is also a favorite of mine. The name implies freedom from spraying, and from disease. Another apple I have is Freedom. The two trees had fruit a couple of years ago when it rained during bloom time and all the other apples had no fruit. Don't ask me how they did it. I think they bloom slightly later than the others, maybe there was more clear weather then.

Some columnar apple trees have been developed that don't get side branches. One of those could maybe be fitted in a narrow spot to give you a pollinator. My supposedly semi-dwarf apple trees are all 15-20' monsters, so heed silver creek's advice.

If none of your neighbors have apples, you will not only need a second apple tree for pollination but you'll need to start a mason bee colony to do the pollinating. You can buy a nest block with bees and they'll take care of it from there. I bought one nest block with bees when I started my little apple orchard, and they multiplied so fast I had to buy new empty nest blocks every year or two for as long as I lived there. They are only out for a few weeks in spring and they don't sting. I loved sitting on the porch near the nest blocks watching them work and fuss.

I also had Liberty and it did very well.

We had a Liberty and others.

The exceptional benefit with Liberty is the color it adds to the landscaping / garden with the red apples.

We had fine pollination from the other apples, with just the local insects - no special imports needed.

Well, Liberty definitely seems to be the one. Now I have to find it! Many thanks for all the help.

One note on Liberty- it is an excellent apple, but tends to set too much fruit. You do need to thin the young fruit to get good size and quality.