Gee,
"Grace" is the only smoke bush/tree I know that will get 20 feet tall. It is a cross between a smoke bush and a smoke tree.
Why don't you just buy smoke TREES? Not the bushes.
Look them up online and see if you like them.
I understand your love of smoke bush and trees, they are truly beautiful.

The straight species gets very large, probably easily 15 feet, but its also very wide. I think you'd lose by trying to prune it into a tree form. Why not just one in that space?

i agree that 3 trees in that space is overdoing it ...

TIMING of pruning is imperative ... that is how you do NOT remove next years flowers ...

this plant is soooo unruly ... that it is going to need constant pruning .... so you will have to learn how to do it ...

i agree.. if you want a tree.. the best place to start.. is with a tree ....

your spot ... and your idea sound nice.. but i am not sure the dream will occur ... it will not be easy ... but dont get me wrong.. dont let that stop you ...

ken

You are looking at two different plants :-) Smoke bush is Cotinus coggygria, native to Asia and typically grows to about 15' if left unpruned. Smoke tree is Cotinus obovatus, native to the US and while often still very shrub-like, can get to be 35' tall. Both can be trained into tree forms and smoke bush is sometimes sold already trained this way in nurseries.

'Grace' is a hybrid between the two species and can get quite large - 25' is possible. But it also has a pretty wide, spreading habit often with multiple stems from the root crown so how likely it will respond to being trained into a tree form is a bit of a guess. You will need to start small if that's your intent. The flowers are the "smoke" effect - pruning back top growth on any sort of routine basis will typically result in a lack of flowers/smoke.

Since you don't say how large this area is, it's impossible to say if 3 of these planted together are too many :-) But even if trained to a single trunked tree form, these do produce a healthy canopy spread - about as wide as tall, if not wider for the smoke bush; about 20-25' for the smoke tree. Plan accordingly.

That's all very helpful. I've been doing research on the tree/bush/hybrid options and have seen a lot of inconsistent information. For instance Taunton's fine gardening says Grace only goes 10-15 feet high and around, but other places it says 25 x 25. So I came here for some experience, not just a web page statistic. It sounds like it can vary a lot.

Yes, the trees will have 15 feet between, just enough for three but a little crowded. I just don't want to allocate the space laterally to just let them grow out. I have plans for the space underneath.

It looks like I should search for a tree form of grace and hope they are on the smaller end of the scale.

darn words.. they mean everything ....

i MEANT.. to start with a plant that is already trained into tree form ...

rather than buying a wild shrub.. and hoping in 10 years that you can 'train' it into tree form ...

that said..

EVERY plant has an annual growth rate ... and most never really stop growing ....

MOST size estimates are at 10 years.. and unfortunately.. they continue growing thereafter.. at the annual rate ...

and that is why.. you are finding no agreement on size ...

read down into the link.. you will see this: Annual Growth Rate: 12 to 18 inches

ergo .. ipso.. presto .... in 10 years ... 10 to 15 feet tall ... which you found ....

in 20 years .... 20 to 30 feet ... maybe ... maybe not.. some things do slow down with age ...

but i have seen the shrubs on centennial farm homesteads .. at least that big if not bigger ... so you will become expert on pruning ...

make sense??

w/o a pic.. my gut is still telling me that 3 is too many ... but make yourself happy ..

ken

Here is a link that might be useful: link

There IS a genetically programmed mature size to most plants......once they reach this internally regulated size, growth slows considerably, sometimes to the point where it is virtually nonexistent, at least to the eye. And I'd say that some size estimates are given for a 10 year period - that is becoming less and less common in the nursery industry as it is proving to be meaningless for the consumer.

Ultimate mature size is very often determined by location and growing conditions. 'Grace' hasn't been around all that long (late 70's) so it may be premature to provide any firm estimates on size, but I've seen very large plants in gardens in my area. I'd allow sufficient space to accommodate for the larger end of the range :-) And again, much pruning will result in minimal flowering so less 'smoke' effect, if that is what you are after.

'Grace' can grow 15' in a single year. I've been cutting mine down every year for the past 3 years. I cut it down twice last year and it still ended up 15' tall. I lose the smoke, but was using it as a foliage plant. I am going to try to move it, and let it grow as much as it wants and hopefully see some smoke.

Is there any harm if the canopies of the grace 'Trees' mushes into each other? There is plenty of space on the outside, but I can only get 15 feet from trunk to trunk on the inside of the triangle.

i dont think mush together is a technical term ... lol

naw.. 15 feet is fine.. trunk to trunk ...

but i wonder how thick the canopy will become ...

i thought there was some element of 'light and airy' so the sun can filter thru ...

and if you are doubling or tripling the canopy.. that might become a pruning issue ....

listen... [to the written word???] .... the bottom line is ALWAYS .... whatever make you happy is fine with us ... but being cheap at heart .. i think 3 is too many ... etc ...

good luck

ken

BTW: the purple smoke bush.. will be green in too much shade ... and you may weaken the color impact if not enough sun gets in there .... the mushing together part ...