You don't also mention how much width you are willing to give this hedge; an equally important consideration for best selection. I am a big fan of the Lavender Star Flower, Grewia occidentalis, which can easily be kept narrow at less than 2 feet in width, is fast growing, and also has colorful blooms. I'd also suggest that a wire fence framework for an evergreen vine such as Star Jasmine, Trachelospermum jasminoides or one of the Trumpet vines such as Clytostoma callistegioides, or Creeping Fig, Ficus repens might be good choices. If you are willing to install a root barrier, even common old Golden Bamboo, Phyllostachys aurea or Pseudosasa japonica might be good choices for such a screen. I often prefer to use a bamboo as a screen rather than a shrub/hedge, because it is less work to keep the width and height in bounds. Podocarpus gracilior is also a much used hedge material in Los Angeles, for good reason, and things like Pineapple Guava, Feijoa sellowiana might also work well for you.

Hi. I'm in LA too. Can the branches be wider than 12" ? Do you need coverage low or just high for the upper level windows? If the plant can only be 12" wide its really too narrow of a space for total coverage because you will only have the stalks (called culms). If you only need coverage higher up and you can let the branches grow out then you have a better chance of coverage. I don't know of any bamboo that will stay only 12" wide at the base. If there is a deep barrier (1' for a clumper or 2' for a runner) then the bamboo will stay where you want it. Or you can put in bamboo barrier and not have to worry about it. Otherwise I would suggest a fence and a trellis/lattice above it, possibly with a vine. For narrow, very upright, shorter bamboos Check out Thamnocalamus, Fargesia nigra, Alphonse Karr, Chimonobambusa marmorea (runner) or maybe Tootsik (runner). Just Google them and you will see lots of photos and info.

First of all, you might want to start posting on the CA gardening forum. There are quite a few SoCal gardeners on it. Second, soil and prep are ALWAYS more important than plants. If you have clay soil it won't drain well and watering so often will create root rot. Yes, new plants need to be watered to establish themselves - so it's a fine line between "watering enough" and "drowning", in this case. Your calla lilies will yellow and go away very soon. They HATE hot soil. They are partial shade plants at best, especially in your area. In coastal CA they bloom around Nov/Dec thru mid-May. "Hercules" gets not only very tall but will grow outwards at a steady rate. I wasn't successful with my own Anigozanthosos (kangaroo paw), but when advice says to prune back after flower, they mean the flower STEM, not the whole plant including leaves. Sage can be pruned almost any time, as far as I can tell. But like rosemary, you want to avoid cutting into the woody stems. Cut it back to a pair of leaves - any pair, just so you don't leave it leafless on that stem. Bougainvillea can be touchy about getting established. They hate being transplanted and it's very easy to harm the rootball because it falls apart easily. Once it's adjusted, you can cut back the watering gradually. "Sulking" won't harm it as long as you water as soon as you see the symptoms of leaf curling, etc. Dahlias are prone to root rot, especially when dormant in winter. With your clay soil you might be better off growing them in pots if you refuse to amend your soil. Watering too often and shallowly is a common error for beginners. Most plants prefer watering less often and deeply, and from underneath rather than above. Good luck!

Thanks so much parker25mv! Looks like we're both on the same page. I'm not planning on planting them in the ground, and I agree that they're too dominant in LA right now. When I was trying to find a suitable screen plant I read through all of the ficus discussion on here and decided against them. Then these fell into my lap, which opens up budget for native CA plants elsewhere so I'm trying to make lemonade. I'll leave them in the half-barrels, but I'm also open to any suggestions to make them healthier. Root pruning has been suggested above, which I'm looking into now. Thanks!