You can......but it is certainly not recommended!! Routine topping of a tree to keep at less than half the size (actually to about a third) it is genetically programmed to grow to will result in a) a deformed and ugly specimen; b) produce a plethora of water shoots; and c) open the tree to increased disease and pest issues.

You will never find a qualified horticulturist or arborist that would recommend this practice :-) Don't Top Trees

Apple trees grown for fruit production are pruned heavily.

Yes, they are pruned heavily, but not to reduce their natural size by two thirds. They're pruned to promote fruiting. Their size is controlled by growing them on appropriate root stocks.

And commercial orchards aren't using the trees for landscape decoration. Last thing I heard about this was there was a shifting going on to growing apples as tall sheared hedges, with workers being pulled along the rows on platforms using tractors.

Why, pray tell, do you want to force a tree to be seven feet tall?

If you want a tree this size, remove the tree you have and either plant a small crabapple that could reasonably be kept to the approximate size you want, or plant a shrub that is likely to reach 7’ and prune it into tree form, something like one of the midsized Hydrangea paniculata such as Limelight.

As others have commented, a tree has a genetically predetermined size, and if you prune too much in any one year it will send out long whippy growth that is unattractive. It will constantly be trying to regrow to the size it “wants” to be.

The chart linked below has several crabapples that will stay more in the range you want as far as size.

https://www.jfschmidt.com/pdfs/JFS_CRAB_CHART.pdf

welcome to the forums ....

as noted.. topping is not preferred .... i call it a haircut ... sorta like a beatles bowl cut ... it leads.. to eventual decline because of all the open wounds over the year ... but all that happens in tree time.. which could be counted in decades ... perhaps you wont be there in a decade.. to care about what happens to the tree ...

but if you do plan on being there.. i think removal and planting of a tree with proper potential.. would be a good idea ... we have all had to remove mistakes.. and reinvest in the solution ...

that said ... it might be a great tree to learn how to prune on ... as i said.. its not a haircut thing... it would be more of a surgical removal of parts of the tree .. with future goals in mind ... its rather hard to explain such.. in words ... think of topiary as to pruning with goals ... those shapes were not created without a long term plan ....

https://duckduckgo.com/?q=topiary&t=ffcm&iax=images&ia=images

ken

"Yes, they are pruned heavily, but not to reduce their natural size by
two thirds. They're pruned to promote fruiting. Their size is controlled
by growing them on appropriate root stocks."

Well, that's not totally true. First, a variety of pruning styles are used when growing apple trees, and frequently pruning is used to reduce the height of the trees. Pruning is definitely not limited to promoting fruiting! Also, dwarfing rootstock controls growth rate, but not really so much eventual size. An apple tree grown on a medium dwarfing rootstock will eventually get pretty large without pruning, it just does so at a slower rate.

I'm not saying it's a good idea to top your crabapple (especially in the way you describe), but it is something that can be done (especially if your goal is to keep it shorter than normal but not necessarily at no more than exactly 7' high). You can make some selective pruning cuts along the way, as it grows, and encourage it to grow more out than up.

That's why I deliberately included the words 'by two thirds'. Clearly regular pruning reduces size to some extent.

the other searchable term.. beyond topiary ... would be bonsai ...

in effect.. what you are suggesting is 'in ground' bonsai .... reducing and maintaining a plant in a much smaller size than nature wants ...

pruning is not that big a deal ... done properly ... which allows the tree to heal.. aka encapsulate the wounds made ... its an art.. more than a science .... and all it takes is a good tree saw .. and some patience and a wing it attitude ... i mean really ... you just remove it.. if you screw it all up .. and thats what a few of us suggested in the first place .. may as well try to learn something along the way ... lol ...

ken

Pruning a tree for fruit production and for ease of harvesting is very different from pruning a garden ornamental like a crabapple. I'm not sure there is any validity in comparing the two! Yes, I do realize that crabs are sometimes grown for fruit production but 9 times out of 10 they are used strictly for ornamental purposes.

Way back when I took pruning classes (from ISA arborists) as part of my horticultural training, pruning a tree to control size to a substantial degree - like keeping a 20' tree to 7' - was a highly discouraged practice. In fact, on the list of reasons 'why' to prune, controlling size was at the bottom of the list.

It's more a matter of right plant, right place. If the tree is too big.....or will eventually be too big....for its current location, then remove and replace wth something that will remain in scale and size approrpriate without a need for constant butchering.

One of the goals, when pruning fruit trees, can be to reduce the size (mainly for ease of maintenance and harvest). Yes, in some ways the goals may be different (final outcome and acceptable results may vary some), but the base issue (pruning to reduce size) is a common factor. I'm not sure we NEED to use the analogy at all, but, since people did (in responses above), I see no reason to try to invalidate their comparison. There are definite connections.