My Zip code is 91741, Zone is 8

My backyard is facing a road, so I need a privacy screen at the earliest. But that is not just the problem.. The trees has to grow at least 12 feet to protect my privacy. This is since my back yard is not plan it is sloped. The lowest point is 6 ft from the highest point where my house is there. The plan area on the lowest point is 4 ft wide & 77 ft long. Now I want to plant privacy screens on that lowest area along that 77 ft.

I am not sure what would be my best bet.. I want fast growing trees but root friendly since there is a retaining wall on the lowest point. I don't want the tree that reseeds and drops lot of leaf..

In my local nurseries, I generally find - Indian Laurel fig, Fern pine bush trees. I do like Indian laurel fig but this is not root friendly.

Next on internet, I find, Thuja green giant and Willow Hybrid (Salix Hybrid).. I am not sure whether they grow in my area or not.. They both grows in zones 4 - 8.. Sine mine is also 8, it is a border line case.

Next, Willow seems to be fast growing, I heard this is not very root friendly..

Any ideas ? What would be your thoughts and experiences with privacy screen trees ? Please share !!

Thank you for your suggesstions. Let me have a look at them.. I appreciate your suggesstions.

Do they grow fast and root friendly ?

"My backyard is facing a road, so I need a privacy screen at the earliest. But that is not just the problem.. The trees has to grow at least 12 feet to protect my privacy.  This is since my back yard is not plan it is sloped. The lowest point is 6 ft from the highest point where my house is there. The plan area on the lowest point is 4 ft wide & 77 ft long. Now I want to plant privacy screens on that lowest area along that 77 ft."

Hi again Cprao, Take another look at Rhus integrifolia. It is very manageable and easily pruned to various heights in addition to being fast-growing, evergreen, and drought tolerant.  Compact Rhamnus californica cultivars may also be considered. I admire Callistemon when in southern California and these Aussie plants are certainly fast growers. The compact Callistemon citrinus 'Jeffersii' is shorter than the standard form and meets your height requirements. Fairy duster (Calliandra californica, www.elnativogrowers.com/Photographs_page...) is a comparable native that's also lovely, but it has a medium growth rate. 

Pruning and shearing can do wonders. For example, compact (or not so compact) bougainvillea cultivars can be trained and sheared as shrubs with no support. Here's a great shot of unsupported bougie hedge I took in San Diego: www.learn2grow.com/plants/bougainvillea-... Ask your local nursery specialists what cultivars they recommend for this.

Good luck!

I agree with Jessi on bougainvilla. It's an easy to grow plant, does well with or without support depending on what you want it to do, trims back easily, grows to awesome proprtions (simply do the research and find the best variations!), root invasiveness is not a problem...pretty much hassle free privacy screen.

Jessica, Sorry for confusing you but thank you very much for your continued feedback.

Following is my requirement -(1) Plant/shurb needs to grow the height of 15 Ft. If they grow taller than than I can trim them. But they should go minimum this height.

(2) They should be bushy not columnar.. expected width of the tree should be 4 ft.

3) The roots should be friendly not invasive.

4) The growth rate of the plant should be 3 to 4 ft per year.

Next, the plant that you just suggested California lilac seems to work.. I believe this will be availalbe in local nurseries. Let me do some more research on this shrub.