Fruit trees of named varieties are propagated mainly by grafting, and all trees sold of that variety are genetically the same tree since they all were vegetatively reproduced (rather than sexually reproduced) from the same original source tree. So, what you have is one Scarlet Spire Colonnade apple tree growing on two different sets of roots. Unless the tree is self fruitful, you will need a genetically different apple to pollinate them. However, odds are there are other apple trees (including flowering crab apples) within 1/4 to 1/2 a mile of you, which will provide the pollen you need and your apple trees should still produce fine. The closer the neighboring apple tree, the better, so trees within a block or next door are best, but it is highly likely there are other trees around.

Bloom time depends on various factors like where you live, including your local microclimate, as well as the particular variety of apple that you have, how much water and sun the tree gets, etc. That being said, here in Wisconsin, you can expect your apple trees to bloom sometime in late May, plus or minus a few weeks. You did not say that your apples bloomed or set fruit this year. If they didn't, I'm not surprised at all, because of the very unusual weather we had in March and April this year -- very warm followed by very cold. A lot of fruit crops nationwide are suffering this year as a result -- the blooms either died, or failed to develop, or had no bees to pollinate them. I have three young trees and I have a grand total of 3 apples. Three years after planting, I expected a reasonable crop this year, but the strange weather, in addition to my regular pruning, prevented much blossom at all this year. I think next year will be a huge crop nationwide, assuming the weather plays nice next spring. As for spraying, I honestly have no experience, and I am trying to grow my apples as organically as possible. However based on everything I have read, there are various sprays that can be applied for all different purposes, but the ones for bugs and beetles often seem to be applied either immediately prior to bloom, or just after bloom when all the petals fall off and before the apples get beyond about marble size. So those one or two points in spring at bloom time might honestly be good enough for what I've experienced here in Wisconsin. I had some woolly aphids this spring and I was able to squish them all by hand since my trees are dwarfs and still fairly small (6 to 8 feet high). Other than that, I had some fly speck (I think that's what it's called!?) that killed one apple, but I haven't had any trouble with my other apples yet. You can spray maybe once or twice more in summer, but as it gets closer to harvest time, well, I guess I really don't know if it will be necessary. One thing I do not doubt -- some people will say you definitely need to spray, and some people will say you definitely do NOT need to. So do a bit of research on the interwebs or whatever, and then do whatever you think is best for what you want to get out of your harvest. Best of luck to you -- if not this year, then in 2013!

where are you in z5?? in my z5 MI .. i would tuck then in on the north side of the house.. when the ground freezes .. i would tip over the pot ... and as i shoveled snow of the sidewalk .. i would bury it in snow .. if any ... the snow actually insulates then from frigid winter winds.. and temp spikes .. they are a deciduous tree.. they were supposed to lose their leaves months ago .. i suspect you may have been feeding them .. trees dont need a lot of fert in a pot ... the sprouting seedling is way out of phase or kilter.. who knows if that one will live.. dormant trees do NOT need a lot of water .. and i tip them over.. so a frozen pot.. will not accumulate rain or melting snow.. in frozen media ... roots need air as much as other things.. and freezing them into an ice cube is not helpful ... and NEVER leave a black pot in winter sun.. it can warm and heat too much ... making the roots come out of dormancy while the rest of the tree is dormant .. this is all about my z5 adrian MI ... and i am sure all colder zone ... ken

There are issues with young apple trees that you just won't have with older, more mature trees. The structural aspects are pretty obvious, a 1" dia branch won't hold the same weight as a 2" dia branch. The laden branches can actually break off, ripping down the trunk. At the minimum, even if you leave the fruit and the branch bends down, it may well just stay that way in the future and not bounce back up. That happened to some of my trees. Another aspect is that the tree puts all its energy into producing fruit, not becoming larger and stronger. And if you're not careful, it can turn into a bi-annual deal, where it skips producing fruit every other year because the plant needs the energy to recuperate. I learned (still learning) all this stuff from having a newly planted orchard and getting advice from all over the place, including the fruit tree forum on Gardenweb. Also, thinning the fruit will give you larger fruit. And taking a hint from the boys on the fruit forum, they cover each apple with those disposable socks you find in shoe stores - keeps the bugs and birds away. I haven't done that yet........