With apples you normally don't have to worry about pollination if you're in town or there are other trees up to a mile away.

I have no idea if anyone else nearby has an apple tree or what varieties they have if they do. So I thought I'd make sure by getting an apple that the crabapple could pollinate.

Most crabapples flower before edible apples. I think your best bet would be to plant an early apple or edible crabapple. Hazen, KinderKrisp, State Fair, Zestar and Whitney (edible crab) would all fall into that category. There are plenty of others too, these are just some of my favorites that bloom early. We usually tell our customers that they will get the best pollination if the trees are 100' apart or less. Here in Minnesota, the apples often bloom before there is much bee activity.

Some apple cultivars, like Rome Beauty, are self-pollinating. The presence of crabapple blossoms nearby could only help them.

I actually looked at replacing the existing crabapple with a Whitney since the fruit are useless and have been dime-sized and diseased both years I've had it. It also has a vigorous sucker that I can't seem to get rid of no matter how many times I cut it down. I feel kinda bad about it though since it looks pretty nice in bloom and I would not be giving it away to someone.

As far as what I decided to do a couple years ago, I went with a Goldrush apple. This will be its 3rd spring. I am going to try my hand at grafting on the Goldrush this year with a Sundance. If I knew what the rootstock was on the crabapple, I could try grafting on it as well instead of replacing.

Actually, I don't think you have to worry about what rootstock is on the crab before you choose to graft onto it unless you wanted a dwarf. If you think your crab is a healthy well growing tree any other apple would graft onto it just fine.

I was thinking about the unknown disease susceptibility and the suckering. But I guess I could always just graft and see how it plays out.

There seems to be always something to think about when dealing with fruit, if it is not disease, then hardiness, then size etc,etc,etc, lol Up here in the frozen north any apple tree that grows well, is gold. :)

I ended up trying my hand at grafting on both the crabapple and the Goldrush with Sundance. Maybe Goldrush blooms this year and I see if it overlaps with the crabapple. Sundance is in the same flowering group with Goldrush. I guess we'll see how all this stuff pans out. :-)

My Goldrush bloomed for the first time today. :-). The crabapple is yet to fully open but it is almost there so I think they will overlap. None of my Sundance grafts have taken yet but I remain optimistic. Unrelated but I have a Korean Giant graft that has taken and also a Superior plum that has taken on a peach tree so I feel good about my first attempts at this.