Does anyone have the ability to tell me a little bit about my Japanese Maple? I moved into a new home last spring and this tree was already here. It’s beautiful but other than my awareness that they exist, I know very little about them so have several questions. One thing to note is that I assume that this is a juvenile tree that is still growing because of the dramatic change in size from last spring to this spring. It was probably 1.5 to 2 ft shorter in height and width last year and, at that time fit its space perfectly. I had hoped it was some sort of dwarf and that it was done growing but, as you should be able to tell from the photos (one is from last year) it’s still expanding. The questions that I have are: Would anyone happen to know how big I can expect this tree to get? Will it being this close to the fence be problematic? Can it be pruned in a way to “contain” its height and width? When would be the ideal time to prune? Is there an option to prune late spring?
I would guess it to be an acer palmatum 'Bloodgood;, though there are several similar varieties. Bloodgood will get to be 15 to 20 feet tall in 10+ years. Even though it can be pruned most any time, I suggest that you never cut it in winter. I prefer to do structural pruning either immediately after leaf fall or first thing in spring (as buds swell). Japanese maples tend to produce two flushes of growth each year, marked by pauses when new growth stops extending. These are prime times to trim for shaping and making ramification (branching branches -> one become two - there is a bud at the base of each leaf that may be released to produce a new branch). But, if you don't want your tree's canopy to become dense and bushy, you'll likely never prune during the season for any reason other that to remove a 'wild hair' of a branch. I suggest that you will not want to get involved with limiting its height because it will need to be repruned at least every other year and that you'll be or you'll be paying someone to be on a ladder or in a cherry picker to do it. It is okay and just up to you. I contain their height to make bonsai, but I generally let my landscape planted specimens grow (height-wise). You've got at least a decade before this tree becomes so big that it will no longer fit your landscape, IMO. It is not likely to do or be responsible for any damage before then Your tree may be planted a bit close to the fence, but you are likely to 'limb it up' (remove low branches) over the coming few seasons so that the canopy is eliminated to some level above the fence. If you are unsure about it, you can just leave it be as the shaded branches between the trunk and fence are shaded and will weaken and die over time. Then you can just remove those dead branches and otherwise prune to expose the trunk to the extent you wish to see it. When you prune to remove a branch, note the collar on the trunk that surrounds the branch on top and around it sides --> do not cut into the collar. Else you'll do some damage that may never 'heal' (btw, trees really don't heal, they isolate it into a compartment and maybe overgrow it - the dead wood will forever be dead wood that is vulnerable to fungal infection / rot)
I agree with everything Osoyoung said and second the opinion that you shouldn’t prune the top of your tree. My personal preference is to do pruning in late spring or early summer. This gives plenty of time for the wounds to start healing during the summer. Your tree is likely to grow into a broad vase-shaped maple if left unchecked. Like the first picture that I attached (from a recent trip to an arboretum, showing a Japanese maple that is not that old, but is very large and with a beautiful shape). If it were me, I would try to help it grow into that shape, instead of fighting it. I suggest pruning almost all small branches below the line that I added to your picture (cut them back all the way to a major branch, or the main trunk if it exists). Leave any major branch that clears the fence untouched, unless you want to change the branching structure of your tree to something else. Don’t prune anything that is above the fence or grows in a way that will clear the fence in the future. My two cents. It looks like a very vigorous tree, it should have no problem tolerating any pruning you do.
We generally prune all of our Japanese maples in early March, before the bud sets open up. If you are in a region with cold weather, then of course wait until the danger of frost is eliminated. Japanese maples can be prune pretty much any time of year depending on your geographical location. Again, if you are in a region with cold winters and heavy frost then limit your pruning to spring and if need be, summer. But of course the best time is early spring (imo) when you can visually see the structure of the tree before the leaves open up. As far as shape goes, it is all in the eye of the beholder, as @Nik mentioned, bring up the lower section of the tree is a very good start. Then selective pruning to dictate how high and broad you want the top crown to be is up to you. Most important, clean pruning shears and a good quality pair that gives you a tight clean cut. With larger branches use a high quality tree saw and apply a light cutting motion so you don't have exterior bark peeling when you finish the cuts.
