I don't know anything about the tree, but I wouldn't pay much attention to internet only ads any more than I would to late night TV infomercials.

I would recommend visiting a few local nurseries and letting them know your needs and comparing their recommendations.

I have 'Thuja Green Giants' here in Michigan. I bought one 3' tall tree, cut 200 cuttings from it and ended up with 135 healthy trees. Planted the cuttings in 1 gallon containers the first year then transplanting them to 5 gallon containers the 2nd year. They require lots of water and fertilizers. They grew from 3-4" cuttings to 3.5' trees in two years in the pots. When planted in the ground they didn't grow much the first two years. This is their 3rd year in the ground. They have grown about 1' so far. I'm told that they take off the 4th or 5th year after being planted and grow at the 3 to 4' per year rate (Information about how to grow these trees came from a tree specialist at Michigan State University). Each year I've pruned them to stimulate root growth-per instructions from tree specialist. Next year they're on their own. They have a drip irrigation system (new this year) with a fertilizer injection pump to keep them feed until the end of August. Probably the reason they began to grow faster.

They require 6 weeks of temperatures below 36F to grow properly. Don't think any nursery in L.A. would stock them. You can order them from Parks Seed Company (link below).

I special ordered mine through Romance Garden Center, Portage, MI and they purchased it from the same growers Park Seed gets them from. It was their first year offered and since then the price has come down.

Get one and try it. Be sure to tell us how it goes. During your coolest period of the year donÂt feed or water them and see if this will simulate ÂwinterÂ.

Protect them from deer/rabbits-they eat them at the end of winter after all the good stuff is gone. So much for Deer resistant!!

Good Luck!
Virgil

Here is a link that might be useful: Park Seed Co

Better retail nurseries typically offer plants that will succeed and thrive in that specific climate location. This is a huge advantage over researching and/or obtaining plants online. That the Green Giants are not readily available in your area nurseries should be an indication that this may not be a good choice for the heat of zone 10/11 southern California. Not to mention the ongoing drought you are experiencing.

FWIW, your query may get more appropriate and site-specific responses in either the California Gardening forum or the Conifers forum rather than one focused on container gardening. I think you will find that there will better and more location appropriate choices for fast screening plants best suited to your climate.