I have a very small (14'x16') enclosed backyard (townhouse) that is east facing. I am planning to create a Japanese-influenced garden, so have been looking at maples and cherries. I love Acer palmatum 'sangu-kaku' but would prefer something with a more horizontal branching structure. For ornamental cherries, I'm really open to suggestions. Help!
Prunus incisa kojo-no-mai as far as im concerned this little beauty would be a must. or what about a cloud tree, see attached picture
You mention the sango kaku as being not horizontal enough. Do you want a very low habit JM? I have a sango kaku here which is about 3 1/2' tall with a span of around 6'. It could easily be pruned and/or trained lower. I can show you a pic if you like. Do you have THE Japanese maple book? By Vertrees/Gregory. I also have the book on Japanese plants which lists something like 5,600 different ones. I'll see what it says about the cherries. I take it you probably only want a fairly small variety?
Consider Prunus tomentosa, Nanking Cherry. Stays shrub sized, lots of cherry blossoms, fits the scale of your garden.
I looked in the book, Garden Plants of Japan, and the first thing I'm going to do is recommend you get a copy. Stone Lantern has it on now at $20 off. I have no association with them other than as a happy customer. It is a Timber Press book, excellent! There is an extensive list of the Prunus varieties, and any one of a couple of dozen would suit you. And almost without exception they are adaptable to pruning to keep them small. Prunus mume comes highly recommended, Japanese apricot. But then, so do many others.
Here is a pic of the sango kaku, taken in the rain, so the bark colour does not show up well. It is 43" tall and 70" wide. It has been in that cedar tub about 5 years, and I think was about a two year old graft when I got it.