Apple pollination question

[AnnaMagnani]

I am trying to buy another super column apple tree for the back garden and getting confused over pollination.

I already have 2 supercolumn apples in the back, both of which produce fruit but I can't remember what they are.

I also have a crabapple in the front garden which I know are supposed to pollinate all apples but how far away is too far? (It's a normal sized house, not miles away)

So looking to buy another tree, everything is helpfully telling me what other trees they need to pollinate but do I need to worry about this?

I know when I bought the original trees I would have made sure they were all in the same pollination group but that was over 15 years ago now.

You could get a self-fertile variety.
Apple Trees For Sale - Chris Bowers
(other nurseries are available)

It's Chris Bowers that is confusing me!

I'll look harder.

Limited To One Tree? These 15 Self-Fertile Apple Tree Types Will Fruit On Their Own | Horticulture Magazine

I can't find one that says column.

Does it have to be an apple tree? I'd be tempted to get a pear tree.
The crab apple is probably near enough for cross-pollination..

My understanding is that the fellow apple trees that help fertilise the primary producer tree(s) only need to be within half a mile. Front to back garden is plenty close enough.

I never heard of super column before, so acknowledge I have only rudimentary info.

Adjacent pollination groups will cross fertilise to some extent. Or you could buy from a local nursery when yours is in flower, though that’s not guaranteed as local
microclimate has a big effect

Thanks everyone. I think it would have been fine with the front garden crabapple but as I've already got rid of a few trees that weren't productive- a pear tree that produced one pear max a year for 10 years for example- I've decided not to risk it and found a self fertile one.

I think the main thing is flowering time so if you know when the existing ones flower you can pick one that flowers at the same time. Not an expert though...

Um, spring time!

As you can see I have not been an attentive gardener.