I grew up in a somewhat rural/somewhat suburban town in SE Michigan, with a lake down the street (and 7 others just in my town) and woods behind the house. I was a sort of mermaid-wood nymph. It was awesome. We are very urban now, just 1 mile from the border of Chicago, with an expressway and an elevated train half a block away. The kids do their best with our yards, treating 4 front yards as one long playing strip (we are all friends in those 4 houses) and going a few blocks to the school if they need a field. It works well enough. So yeah, we do have to be mindful of that when planting. The house I grew up in had several trees in the front yard, but the yard was so big it didn't matter. Our current house had bushes along *both* property lines when we moved in, but we removed the ones separating our yard from the other yard with kids (the opposite house, that is in danger of being eaten by its tree, has no kids). kitasei: when you say "yours may be an Olmsted," do you mean the sapling? I would be very impressed if anyone could identify that tiny tree at this point. I have no idea what it is. When they took out our ash, we put ourselves on the "new tree list" and 6 months later came home to a sapling. I think they are being careful about what they plant now, having found out in hindsight that planting a row of just one kind of tree is a very bad decision. I still miss the tree canopy. It was beautiful. I also had another look at the parkway and don't think there is enough space for an additional tree, because of the placement of our neighbor's tree (you can't see the tree in the pic but you can see the shadow) and the tiny sidewalk to the street. I will make do. At least the sapling is kind of in front of our house. Down the block, where 2 neighbors' mature but dying trees were taken down, the parkway sapling got planted in front of the 2 houses' side yards. Those 2 houses are essentially sharing a tree, which won't provide much shade for either house as it grows. That's unfortunate, but it was the only place on the parkway they could plant a new tree because of where the other 2 had been.

Tread carefully with what is presently planted. Kinnikinnick (also called bearberry) is very difficult to transplant and your hillside is providing the necessary growing Zone 2-6 acid soil and light conditions for it to thrive. Additional plantings must be added with care. Knowing your growing Zone number or what major city is close by is necessary for a number of reasons. This healthy hillside planting is an uncommon landscape feature that will only thrive in certain areas. General location of this property will help us to prevent you making mistakes.

Rock gardens provide excellent drainage, so in theory would allow you to grow plants that can’t make it in Houston’s heavy, mucky, clay soil. However, rock gardens in Houston are tough, mainly because of the torrential and violent rainfall. Any soil you pile up, and any mulch you place will get washed away. Large decorative rocks are pretty in most parts of the country, but in Houston they grow mold and mildew, so pick dark colored ones or you’ll be power washing them along with your driveway. Add some searing heat and deep freezes, and you’ll see why you can’t design a California landscape and succeed with it in Houston. So, I’d look around at what succeeds in the Houston climate. Holly ferns, azaleas, camellias, crape myrtles, and mondo grass. You can make an attractive and easy-care landscape, but stick with the few stalwarts that thrive in this climate. I’ve lived and gardened for decades in many parts of the country and the best advice is generous planting beds with lots of mulch populated with plant species that thrive in the local climate.

Low growing junipers would also work. They come in a variety of colors, like these "gold" one in the foreground. I am not sure if these are right for your zone. But there are evergreens that have been bred to remain low, so if you had a few the space would not seem bare when the other plants are dormant. Green: Spreading light green conifers are 'Golden Pacific' shore junipers (juniperus conferta). The mounding bluish conifer is 'Feelin' Blue' (deodar cedar).