Long shoots on deciduous

[Charlo]

I am used to the growth habit of pines and junipers. This season I have acquired 3 mame crabapples and one big Amur maple. All 4 of these trees have put out one vertical long shoot each. I give them morning sun, but it is very hot so I do not let them get too much sun. My question is when do I cut these shoots? Why do all 4 only have 1 each?

 

[Shibui]

Without seeing the trees I'd guess that your trees are showing apical dominance. They want to grow tall so if one shoot gets going the tree puts all its resources into growing that shoot as tall as possible. Regular pruning can help redistribute that effort into several branches.
Crabs also have 2 types of growth - vegetative which is long, thin shoots and fruiting spurs which are short shoots that will have flowers each year. Remove long vegetative shoots whenever they get more than 4 nodes long unless you are trying to thicken or extend branches.
Just morning sun may not be enough for these trees but that will depend on where you are and how hot the afternoon sun is there.
How much fertiliser? It is possible the trees don't have enough energy to grow many shoots?

Adding your location can help with advice.
Pictures also help give more clues to what's happening.

 

[Charlo]

Without seeing the trees I'd guess that your trees are showing apical dominance. They want to grow tall so if one shoot gets going the tree puts all its resources into growing that shoot as tall as possible. Regular pruning can help redistribute that effort into several branches.
Crabs also have 2 types of growth - vegetative which is long, thin shoots and fruiting spurs which are short shoots that will have flowers each year. Remove long vegetative shoots whenever they get more than 4 nodes long unless you are trying to thicken or extend branches.
Just morning sun may not be enough for these trees but that will depend on where you are and how hot the afternoon sun is there.
How much fertiliser? It is possible the trees don't have enough energy to grow many shoots?

Adding your location can help with advice.
Pictures also help give more clues to what's happening.

Thank you so much for this informative message. I appreciate it. Next time will add the info.