Most columbine are somewhat adaptive to a range of soils, although I suppose there could be some species that require a more alkaline soil...there are many. No, I don't think putting a barrier around the rhododendron would serve any purpose, and as it grows, the roots will grow to extend out as far as the widest branches - rhododendrons have a surface network of wide, shallow feeder roots you wouldn't want to restrict. It's hard to answer your questions though with no gardening zone known for you, and you don't say what your approximate soil ph might be now. I don't know if you are in a harsh winter climate and trying to grow a rhododendron that isn't bud hardy for you there or just why it may not be flowering. They are not heavy feeders and will often need no fertilizer in soils of average fertility. Additional nitrogen is rarely recommended unless indicated on a soil test - nitrogen can even be counterproductive to blooming, directing the plants energy into foliage growth, buds. Drought in summer when buds are being set can cause failure to flower. Adequate water, moisture, but in soil that drains well and doesn't remain soggy is needed. Pruning at the wrong time of year, too much shade will result in no blooms. And as above, wrong plant for hardiness needed for your climate.

jowall, Above I showed how it could be done, but I wouldn't do it. Think about the access to those flat terraces. Lots of steps to build. No easy way to get a mower or wheelbarrow on them. In short, it's a access, maintainence nightmare. I think I would be satisfied if the slope could be modified from the current 5 to 1 to a 10 to 1 (horiz. to vert. ratio). If the grade work is extended past the ends of the house then a ramp can be done to gain access to the two modified slopes and one set of connecting steps as shown below.

THANK YOU everyone for your all of your thoughtful insight. hcmcdole: I really like your idea of trying to grow them as a free form esapaillar. Or what if I just prune REALLY aggressively on the backside???... So here's what I'm thinking I'm going to do: I am going to prune REALLY aggressively on the backside of the plant to minimize it's growth and spread against the wall... Do you think this would work??? I don't mind how much if it wants to spread forward away from the wall or side ways in width. I would also like to minimize and maintain about a 5 foot height... That way it can overlap the bottom edge of my windows... And I can see the flowers even from the inside of the house. Is limelight the kind of hydrangea that will respond well to pruning and shaping during the growing season??? I know that I would probably make my life a whole lot easier if I just got the Little Lime variety... But it was nearly twice as much for a 2 gallon... Which isn't in my budget. What do you all think??? Am I going to be sorry years from now for even considering this idea and thinking I can keep Limelights growth maintained with pruning during the growing season??? I've never had much luck with hydrangeas in the past... So it's difficult for me to fathom a hydrangea that will grow 8 feet tall and grow so quickly.

This might have been mentioned. (I didn't read everything.) If you had a groundcover below the trees, there stands a good chance that many leaves would disappear into it as they sift down, and then just convert to "mulch" over time. I don't think it looks good to have shrubs below the trees as it seems everything is competing visually with everything else. It could either be a tree form with groundcover below, or a shrub form that is allowed to cover all the ground space. Whatever plant (tree or shrub) you pick, if it's reasonably narrow, I wouldn't worry about some if it crossing the property line as that's just the way life is with limited space yards. It happens everywhere. The neighbor has the right to cut back to the property line. Also, I wouldn't worry that a plant is labeled necessarily as "tree" or "shrub". For small trees and large shrubs this is a massive "grey area." Many plants can fit either category depending on how you prune them.