Ask Mr. Smarty Plants

You have given us lots of problems to solve to find you a tree for your pool area.  First of all, unless we recommend ferns or some kind of conifer, the plants are going to have flowers.  As for invasive roots, conifers and oaks tend to have large tap root systems that are not as likely to grow into your pool area.  The do also grow lateral roots as well as the tap roots.  The roots of other plants are variable and we don't know exactly how they will react in your area.  It will depend on where a water source is for them.  Since you are going with a relatively small tree, you could consider growing them in large containers so that the roots are not a concern. 

With all the above in mind, here are a couple of smaller conifers that you could consider:

Juniperus californica (California juniper) and here are photos and more information.

Pinus attenuata (knobcone pine) and here are photos and more information.

Here are a couple of small evergreen oaks:

Quercus dumosa (coastal sage scrub oak)

Quercus durata (leather oak)

Many (if not all) of the plants below may attract bees to some extent.  Flowering plants need pollinators and many pollinators turn out to be bees of some sort. Bees are not normally agressive unless you disturb their hive.  However, if you are especially allergic to bee stings, I can understand your concern. You may have to resort to some sort of conifer or one of the oaks above.  Conifers and oaks are generally wind pollinated.

I assume you are looking for an evergreen tree so I have only chosen evergreens—the ones above and the following ones.  If you would like to consider a small deciduous tree, please visit our California-Northern Recommended page.  You can use the NARROW YOUR SEARCH in the sidebar to choose 'Tree' or 'Shrub' under GENERAL APPEARANCE to find various recommended small trees or shrubs that are commercially available and native to Northern California.

Morella californica (California wax myrtle) grows 10-25 feet but responds well to pruning.  It can even be made into a hedge.  Its botanical synonym is Myrica californica and you can see a photo and more description at Bay Natives from San Franciso area, one of the Associates in our National Suppliers Directory that specialize in plants native to the area. Here is more information. 

Another evergreen shrub/small tree with berries is Frangula californica ssp. californica (California buckthorn.  You can see a photo under its botanical synonym Rhamnus californica at Bay Natives. 

Heteromeles arbutifolia (toyon) is evergreen, but comes with lots of berries.

Garrya elliptica (wavyleaf silktassel) has male and female trees.  The male trees have the long tassel-like flowers.  The female trees have smaller flowers, but will have berries.  Here are photos and more information.

Arctostaphylos manzanita (whiteleaf manzanita) is an attractive evergreen small tree. Here are photos and more information from Las Pilitas Nursery from our National Suppliers Directory.