What zone are you in? If you are only zone 5 (this is the Northern Gardening forum so it's a possibility) you likely won't have any problem with extra growth because it will be at the edge of it's hardiness zone.

I agree with you gardengal, not to mention in my above post I errantly assume the owner will stay in the house indefinitely. I agree with the dwarf varieties. It appears to me that the yard isn't very big #1 so I doubt it is an insane amount of work. Its a huge focal point as it appears to be by the front door, about 12-14 foot long length by 8-6foot down to 0 wide, and a small grouping of lower growing Japanse Maples like a Tukeyama and Waterfall variety grouped together and trimmed once a year EVERY year would be pragmatic. My mom has a 40 year old 8 foot Tukeyama in full sun all day zone 9 FL gulf coast in an area half that size granted we have taken turns pruning it for its entire life. The Sun only reaching the front corner for one hour is a very good thing so I expect if you plant one the plants will reach up towards the sun so i would plant slightly closer to the wall than the walkway. Pad compaction could be an issue so I would be sure to amend the soil when planting. I would also be concerned about prolonged periods of drought as the bed is probably cut off from irrigation. A cheap irrigation design is to get 2 gallon food grade supermarket buckets, attach capped pvc running from the base of the base of the bucket perpendicularly, drill 1/16th in the pvc, and burry the line underneath the trees. Make sure you have a cap for mosquitoes and you can even put an ornamental pot on top or in front of to hide the bucket. Makes a great way to apply liquid fertilizer.

The potential for damage certainly exists but really only when planting. Once in the ground, the roots of the geranium will co-mingle quite peaceably with the JM. So try to minimize the disruption as much as you can. Pre-plan the placement to avoid any major roots, plant small if you can (4" or quart much better than a gallon) and as small a quantity as you feel you can get away with. Don't opt for full coverage immediately - the geranium does spread and quite handily :-) And doing this planting in winter while the tree is still dormant will present the least disruption to the roots.

It's true that months ago I was wondering about whether I should remove my own beautiful white bark birch tree. And now the city birch tree has rotted and is in the process of being removed. So why would that upset me? That's one less tree and that's good! I am upset because I don't want a replacement tree planted on my front yard! I have enough tree canopy and tree roots on my property. The tree bylaw has made it very difficult for property owners with trees to remove any tree (even if it poses difficulties for the homeowner and damages their property). Most of all, I ask myself, why it is that homeowners with trees have so many restrictions in regards to what they can do with their trees and are even penalized by having to pay for permits to ask for a tree to be removed; require replacement trees---sometimes one, but mostly 3, or 5 or more to plant on their property if one tree is removed etc. Whereas those homeowners with no trees can remain treeless and suffer no ill effects if that is what they choose. The property right across the road from me has no trees on their property. I say, why not have the city plant "my" replacement tree on the city portion of their property? The homeowners with trees support the tree canopy, but the city only makes things difficult for us by enforcing a lot of rules about how we manage our trees, what happens to our trees, how many replacement trees we would have to plant, where we can plant them and a very restricted list of trees we can choose from. Not a good picture, but might give you an idea of my tree canopy: The red marks the only grass you can see from this aerial view. Trees are living things. They grow. Things change. I don't hate trees. I think they are wonderful. BUT they need to be planted in the right place! It just may be that my Japanese Maple will be happier without the one birch tree. We will have to see what happens. I like your idea Bill of removing the 2nd birch tree and adding an accent tree or something of interest in the yard. This season we will just wait and see what the difference is now that one tree is gone. We had planned to remove at least one of the 4 trunks of our own birch tree to allow more sunlight to reach the garden. We will decide on that later too.