The Viburnum shouldn't need any routine pruning at all if it is planted in a suitable place i.e. big enough to accommodate its natural habit.

There are various different smoke trees but basically, if you want lots of colourful spring/summer foliage you would occasionally need to prune quite hard. If you are more interested in the 'smoke' less pruning would be needed. Your pruning decision would also affect whether you get a shrub or small tree eventually.

Bottom line is that, other than cleaning up broken or crossing branches, you don't actually need to prune either of these shrubs at all if they are planted in a suitable place to start with.

As far as care other than pruning is concerned, we don't know where you live or your growing conditions so we can't make any suggestions as to whether either would need irrigation in your garden. If they would perhaps you should look at other choices.

Shrubs rarely need any fertilising.

p.s. Is there any reason you can't have both?

In addition, you don't state your zone, but even in zone 6, purple smoke bushes, no matter what cultivar, do best as cut back shrubs. They will not bloom that way but will have beautiful foliage. The straight species is much hardier, but I think you'll have trouble finding one to buy.

how much space do you have???

both can get to extreme size .. unless a known dwarf is planted.. and even those can get rather big ... its just a question of how long it takes ..

ken

V potential: https://www.google.com/search?q=Snowflake+Viburnum&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjC0aD9mpPLAhXLJR4KHdqWB8UQ_AUICCgC&biw=899&bih=745&dpr=0.9

SB potential: https://www.google.com/search?q=Smoke+Tree&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjfnv-Pm5PLAhWEsh4KHdiGDx4Q_AUIBygB&biw=899&bih=745&dpr=0.9

I am very sorry that I did not tell you where I live, I live in Northwest Ohio in Zone 5A, I like the purple smoke bushes or tree. It would go almost right under power lines and that would cause a problem when it got 12 foot tall. Is there a Purple Smoke Tree or are they all bushes? Which one would give you all 3 or 4 seasons of color?

This is going into a garden and the way they draw up the plans they give you the chose of either bush. What I read is if you prune the Smoke Tree or Bush it would not get any taller but would send up suckers is this right?

Yes I am looking for color throughout the year and that it really looks outstanding, there will be flowers and bushes in the gardens, there are 2 gardens that will join each other with a sidewalk between them.

When I look at a tree it has one trunk and bushes have many trunks.

Ken I would love to have a tree instead of a bush but the power lines are my concerns. I hate it when the power company butchers trees that are close to the lines.

If there is a that only gets 10 or 12 feet tall I would be very happy with that one and yes even if there are 3 trunks to the tree.

my point was... echoed by others .. NEITHER is a carefree plant ... they will need maintenance pruning ... every year or two ..

and as you note ... what you might be able to do for a few years ... might become overwhelming in the future ...

part of your confusion.. is your reliance on common words ...

Cotinus coggygria 'Royal Purple' is a flowering shrub .... which thru aggressive pruning can be made into a tree form ... you will do much better with WWW searches.. using the latin name ...

you allude to some plan others have drawn up for you .. its really hard to be too specific in helping.. not really knowing the plan ..

i planted a smoker in near full shade ... pretty small plant... about 6 feet from the house ... who knew ... inside a few years.. it was over the gutters ... and rubbing on the house and windows ... so i cut it to the ground... within a couple more years.. with no insult to the roots... it was right back to the same ridiculous size .. i solved the problem.. by moving.. lol ...

i wouldnt mind another.. on my 5 acres .. frankly .. if you dont have an acre.. it might be too big for you ... unless there is a dwarf version ...

and growing them in the full sun they prefer.. they will grow even more aggressively ...

i have also seen Vs.. that are as big as a house.. given a few decades ... left to there own devises ... though again.. i am sure.. they can be tamed thru aggressive pruning ... i do not grow Vs.... but i suspect.. there MIGHT be dwarf versions ... which will still get big given decades ... but at a much slower rate ...

ken

The way it branches cutting back a double-file viburnum every year or two will quickly spoil it. I'm not wild about the Hydra Effect result of hard pruning of smoke bushes either. If there is a 12 ft. cut off and it doesn't freeze back in your location the smoke bush could turn out to be too large growing.

I live in town and the garden is in full sun. the soil is clay loam with what you have said makes me think that I do not want to have anything that is aggressive. But I would love to have a slow growing bush or small tree that would give you color all year along.

Would it be OK to go back and ask them if there is any small tree or bush that would fit there better?

I really like the whole layout what they have done.

I have had plans draw up over the years for the same gardens and never like them until now.

In fact, none of them would come out to look at the area until I contacted this company. All the other ones just wanted was pictures. I feel that when a person comes out and see's the whole layout it gives them a better perspective of what they are looking at.

If you have any ideas that would help me in getting the thing so they would look beautiful it would help. After all, they should be open minded to what you want right?

Neither of your choices would give you colour all year long because they are both deciduous. For that you'd need evergreens, heavy berrying shrubs or, at the very least, something with special bark.

The Viburnum isn't aggressive. And as Embothrium said it doesn't need routine pruning. That would just ruin it. In my opinion it is pretty much a carefree plant providing it is given a good site in the first place. The ultimate size could be 12 feet but not for a good few years. (Are your powerlines really that low? Sounds very dangerous.)

The lines are most likely 20 feet but there is phone line that is lower. So you see you don't need something that would cause problems.

None of the purple smoke bush cultivars is going to get anywhere near 12 feet in zone 5. It may even have trouble surviving a hard winter, and will certainly have severe dieback even in a normal winter (whatever that is anymore), which is why my previous post suggests using it only as a cut back shrub. The smoke TREE, Cotinus obovatus is a different thing entirely, grows differently and will be too large for the 12 ft. ceiling.