the simple term 'shade' .. really means little to nothing ... when we cant stand there and see it ...

is anything else growing there???

how low does the JM hang down ...

could you give us a pic..

and why a shrub .. as compared to any other plant????

shade never really kills anything... it just makes the plant grow slower.. for lack of enough energy ... so i wouldnt worry too much about what might make you happy ...

ken

...and you are located where?

I am also not sure if under a Japanese maple would be particularly good for the maple or the shrub. J. maples have a lot of shallow roots, so disturbing the roots to plant a shrub wouldn't make the maple happy, and competing with the maple roots wouldn't make a new transplant happy. If it's outside of the canopy's final size, you may be fine. As Dave said, without information on where you are (zone and general location) it is difficult to make suggestions. You can add your zone & location info to your profile under "About me".

Aucuba can grow in full shade. The "Mr. Goldstrike" is a pretty one.

my neighbor has several of those yellowish arborvitae shrubs growing directly under their jap maple. They do just fine and look great

--- shade never really kills anything... it just makes the plant grow slower.. --

The sun-loving plant can become so stressed in full shade it becomes susceptible to diseases, insect attack, root rot, etc. That is a bit more serious than just growing slower.

Sarcococcus seems to do much better with shade and hurt by too much Sun.
Light shade is also, to my knowledge, required by Edgeworthia.

How long ago was the JM planted? Like Nhbabs said, root competition will be tough. It's hard to even dig anywhere under a JM. I planted my shade plants pretty much at the same time as the tree which worked well. I could never add anything at this point and certainly wouldn't be able to dig in anything other than a small annual. Could never dig a hole large enough for a shrub.

That being said, dwarf sarcocca is quite nice in the shade and low-growing. I have a pieris near mine alnong with epimediums nearest the trunk since they're OK with really dry soil, then a smattering of hellebore, trillium, European ginger, goldenseal, and I'm sure some other perennials I'm forgetting. Wood's aster does well in dry shade too and is a spreader. Hosta failed in that area.

Again, it will all depend on if you can even get a trowel or shovel in the soil.

Japanese maples have extremely sensitive and delicate roots and I would avoid any serious digging or planting in the immediate area. It is not an issue of root competition - the root system of a JM is pretty tame compared to other maples and the ability to dig is not an issue - it is more a case of root damage to the maple when planting in its surrounds, which is a perfect entree for various soil pathogens to take hold. This is a very common way to introduce Verticillium Wilt which is invariably fatal to JM's.

Ideally, one would want to do any complimentary plantings at the same time you plant the maple. Barring that, I'd suggest some sort of spreading groundcover, like the epimediums or the ginger or pachysandra. Even the dwarf/low growing sarcococca (S. humilis), as that spreads nicely from underground rhizomes. Any shrubs you want to include, locate at the outer edges of the maple's root zone.

I'm not sure why anyone would offer suggestions without having any idea where the OP lives.