When to trim this "tree"?

Skylark001

This dark-red-leafed tree was a very tall and thin specimen a year ago when we moved in, and because it was about 20 feet high it was incongruous with the surrounding shrubbery.  So I cut the trunk six feet above ground level, and hoped it would recover by bushing below the cut.  Thankfully it has: sending out lots of new spikes about 2 feet long.

So once the leaves have dropped this autumn, I'm wondering:

1. When should I trim the new spikes?  By the end of autumn, or in late winter?

and

2.  How much should I remove of each spike, given that I'm aiming for a large, bushy, vertical oval shape?   Should I remove just a couple of inches from each tip?  Or should I be really daring and leave only about 5 inches of each spike?

Thank you for any helpful suggestions.

GardenerSuze

@Skylark001 Do you know what your tree is perhaps a close up of the leaves would help.

Fairygirl

I agree. Advice is really best when there's an accurate ID. 
For example, pruning at the incorrect time can cause problems. 

Skylark001

@GardenerSuze and @Fairygirl, sorry, I should have added close-ups.  Here are two.

Uff

It looks like prunus royal burgundy. I pruned mine about 5 weeks ago as it was badly out of shape because of the wind direction. Looking much better after pruning by two thirds of most of the branches. Mid summer apparently is the best time for pruning. I'm reconciled to giving it a tidy up most years from now on. 

Skylark001

@Uff, thanks for that ID.  I've checked the RHS site and, yes, it does look like a prunus royal burgundy.  I see that's the RHS say, "Prune in mid-summer if silver leaf is a problem".  So that's a second mention of mid-summer.  I'd better get on with it then!  How much is it safe to take off each branch?  

Uff

I would guess that once it gets to the size you want it then keep it that size yearly by trimming off and keeping it a good shape. That's what I intend to to with mine. 

thevictorian

Pruning in summer limits growth while prunning in winter promotes it. With a cherry you are kind of in a tricky situation so I wouldn't be that ruthless and instead consider trying to shape it over a couple of seasons instead and then limiting the growth further by cutting the tips back each year. It will probably survive a really large prune well but will take longer to regrow to a decent size. 

When I prune I take what I think is the minimum off, leave it a while before I get carried away, and then decide if more needs to go. It's easier to take more off than put it back on.

Skylark001

@thevictorian, thank you.  Yes, I think I will let the tree recover from last autumn's severe chopping by letting its leaves do all the work they can until they drop off this autumn, and then I will quickly do some judicious trimming.  

In your experience of this tree, do you know if it is one of those that will send out new shoots from the sites of the cuts, or if it will send out new shoots all along whatever amount of branch is left between the trunk and the site of the cut?  

Dovefromabove

Not a good idea to prune cherries and other prunus in the winter due to the risk of Silverleaf disease. 

Cambridgerose12

Just for future tree-planting info: many species and varieties do exactly this: they grow upwards quickly in the early years, then bush out once they've reached their final height. A flowering cherry isn't a shrub and it will get around 5-6m tall in maturity. It's usually best to let them get on with it, as they will take on a better shape: but it does take a bit of patience. I love the foliage on your plant, by the way.