If it doesn't improve within a couple weeks, I would replant it on a raised bed, protected from wind somewhat or keep it in a pot. Add something to the dirt that promotes aeration and drainage. Expect the tree to take a couple weeks to recover after transplanting. I use a mix created by Al here on the forums, its works great and its almost impossible to over water using the stuff on a raised bed or potted. Click the link at the bottom of the page for info on Al's mix. If you need to find the stuff, I have gave you some ideas below. 1. aged pine bark - home depot sells soil conditioner which is this exact stuff. Make sure it says on bag aged bark whatever you buy. Regular Pine fines bark will work if you can't find this. 2. Chicken or Turkey grit- available in small bags at tractor supply company. If you get a big bag look for it at chick feed store. Which ever kind you get, make sure its crushed granite and bigger than BB size as in the BB of a BB gun. 3. A Turface substitute for small batches is Aquatic plant soil found at Home Depot or Schultz soil conditioner found at Ace Hardware. Here is a link that might be useful: Al's gritty mix discussion

It is certainly NOT to late to plant out ...but a small plant may be better served by potting for at leasst this season...but it will probably not grow that much this year anyway...but if you do plant it out you'll have to really protect it next winter and really care for it constantly this summer. I am a firm believer in planting out older JM's with more established root systems and have had mixed results with small ones not only from overwintering but summer stress vermin constant watering etc ...they are like chilren and require more closely watched care ...and by waiting gives ya time to prepare the area whether a raised bed or just digging out a 3-4 ft area 2 or more feet deep and back filling with more suitable soil which is what I would do Bark is fine but if your clay is like mine it's sort of like oil and water they just don't mix at least I have never been able to and end up just digging it out putting it on a tarp and dumping it in back somewhere ..i would get a load of good top soil or buy some bags and add pine bark to that( if ya wish) or find some descent soil in another part of your yard to transplant if available...but then I am not a raised bed guy others may be.If ya want the link to container soil mixes email me directly I am tired of posting it !!!! David

I don't think you have much to worry about with the roots. The root systems of Asian maples are not particularly aggressive and like most trees, if they encounter an obstacle - the retaining wall - they will simply grow off to the side. To hasten the tree's 'drape' over the wall, I'd remove any staking ASAP. That will allow it to assume its natural cascading habit. And typically, one side of a weeping maple generally has a more pronounced weep or drape to it than the others, so I'd position the tree so that face is placed next to the wall. FWIW, I grew one of these from a 4" potted seedling as a container plant for many years. Aways had to have it on a raised pedestal as the branches extended far longer than the container height. When I moved houses/gardens, it was too big to easily transport the distance to my new place so I donated it to a friend's garden where it was planted in exactly the same situation you describe....cascading over the top of a block retaining wall, where it looks stunning. This selection also gets some of the best fall color of any Japanese maple I've ever encountered. You'll be very happy with it.

I agree with everything that has been said above EXCEPT I wouldn't put on the south side ...even winter winds from the south are COLD in our zone...I don't plant ANY of my JM's on the south side of my house for two reasons . I have a corn /bean field accross the road and there is NO wind blockage so leaves of most of my southern planted trees are damaged jm's would be REALLY hit ...(and overwintering plants would also be subjected to constant winds)... ...also if you are like me in the country, you are LIKELY to be herbicided...jM's don'rt like this either especially young ones. roundup will really hurt young JM's///and herbicide can not only be wind carried ( farmers and chemical applicators are not real sensitive to wind speeds but rather their own speed in spraying the field!!!) but can jump from field to field leaching out of the soil.The only possitive thing is that roundup is much less of a hazard to most trees than alot of the stuff used in the past ...not to say its good by any means, but NOT as damaging. So I think the caviat would be if you have some wind blockage on the south and don't live in the country south planting or overwintering is fine ...but if NOT I'd keep them on th east during the winter and think twice for south planting during the summer. David