Advice From the Help Desk of the
Master Gardener Program of Contra Costa County
Responding to Client's Phone Call Request: Thank you for calling the Master Gardener Help Desk with your question about replacements for your fallen oak tree. You were especially interested in our recommendations on small trees, possibly bigger “shrubs” vs. trees, planting them in a row (as many as 14), multi-trunk vs. single-trunk, overhead powerline friendly, and of course, drought-resistant. I think you are on the right track looking into multi-trunked plants such as upright manzanita, as 14 of those might make a more pleasing landscape than 14 standard trees. Since you have powerline considerations, you also need to be mindful of the eventual height of the plants.
You do have many choices, both evergreen and deciduous, for replacements for the old oak. The PG&E publication (Guide to Power-Wise Tree Planting... you can click the link at left for information on obtaining this free publication) that you have is an excellent resource for options. Some that would do well in central county as well as most of the county include western redbud, manzanita, strawberry tree (Arbutus unedo), California laurel, and crape myrtle. All of these have low or fairly low water needs, but the strawberry tree will also do well in a lawn. Another tree that isn't on the list, but would be appropriate, is Chilopsis linearis (desert willow). This tree has beautiful flowers that can range from white to rose to purple. It requires little water, so is a good choice for a drought-adapted landscape. All of the trees I mentioned can also be trained as single-trunk standard trees if you have a place in your landscape where that might be more appropriate. Toyon (Heteromeles arbutifolia) is another shrub that can grow to be a multi-trunked tree to 25' tall and wide. It takes pruning well, so can be shaped to fit the space.
Source: ucanr.edu