Here are some examples of street trees in Houston. This isn't meant to represent the city canopy overall. While neighborhoods around the city have long had nice tree canopies, street treescaping has improved noticeably in the last decade or so.
This is a Google Streetview image from the med center area, showing recent landscaping of the median and side rights of way.
[IMG]
Houston Street Trees 1 by
dharper615, on Flickr[/IMG]
Source: Google Streetview:
https://www.flickr.com/photos/404119...n/photostream/
This is a view along Sunset Blvd near Rice University. These are fairly old live oaks, which grow slowly and sometimes don't get really large until they're 100 years or more in age. They can spread greatly, but don't get very tall. They provide a nice canopy and are popular in southern cities.
[IMG]
Houston Street Trees 2 by
dharper615, on Flickr[/IMG]
Source: Google Streetview:
https://www.flickr.com/photos/404119...n/photostream/
This is along Kirby Dr. which runs through River Oaks. The neighborhood itself has many tall and very old trees, but the median landscaping is relatively young, and so much better than just grass as it once was.
[IMG]
Houston Street Trees 4 by
dharper615, on Flickr[/IMG]
Source: Google Streetview:
https://www.flickr.com/photos/404119...n/photostream/
This is in front of the River Oak Shopping Center, which has been present for many decades. I don't know how old the palms are. They don't look mature yet. Highland Village has similar palms along the street.
[IMG]
Houston Street Trees 7 by
dharper615, on Flickr[/IMG]
Source: Google Streetview:
https://www.flickr.com/photos/404119...n/photostream/
Finally, this view is in a quiet residential and hotel area in the outskirts of Uptown, just on the other side of Loop 610 that defines the boundary of the inner city ("Inner Loop"). This landscaping is new.
[IMG]
Houston Street Trees 6 by
dharper615, on Flickr[/IMG]
Source: Google Streetview:
https://www.flickr.com/photos/404119...n/photostream/
The above are just a few examples. The streetscaping is expanding to many areas of the city, including Downtown and Midtown, and many residential areas. Some of the Inner Loop boulevards have been treescaped for a long time, although improvements are currently being made.
To me, good treescaping or landscaping within a city is extremely important. It not only makes a city more attractive, but also has a positive effect on people as they drive, cycle, or whatever they do to move around (not that it can completely overcome people's bad moods in traffic!).