Botanical name: Quercus agrifolia
Common name: Coast live oak
USDA zones: 9 to 11 (find your zone)
Water requirement: Light; existing trees usually suffer if watered in summer.
Light requirement: Full sun
Mature size: Potentially enormous with time — up to 70 feet tall with an equal spread
Weaknesses and tolerances: Susceptible to oak root fungus; avoid summer watering. Subject to defoliation by oak moths. Most serious is sudden oak death, a pathogen that has been killing thousands (or millions) of Northern California’s coast live oaks and related species for the past two decades.

Distinguishing traits. On hilltops and valley floors, its dense canopy of foliage and thick trunk create an unmistakable image of the disappearing agrarian and wild California.

The evergreen leaves are oval, stiff and spiny. Note here in this patch of suburban open space that grass doesn't grow beneath the tree, and that fallen leaves create a natural mulch — an attractive and healthy situation to emulate in a garden setting.

How to use it. A live oak is a shade maker, a tree to build a fort in, to climb in, to hang a swing from. Younger trees, as in this design by Blasen Landscape Architecture, look perfectly at home in wilder or casual parts of a garden.

Because of their size and untidiness (dropping leaves, catkins, acorns), live oaks are best at the edge of property, in a somewhat natural section. Don't plant lawn or ground covers under existing old trees; this encourages root diseases. It’s also better not even to pave the soil surface. Trees that you plant generally withstand garden watering better; try to avoid summer watering. Mulch, gravel or stones undeneath, as shown here, is healthier and looks more natural.

Live oak thrives and looks best with other California natives and Mediterranean plants, such as manzanita, ceanothus, lavender and rosemary. Pruning out whole branches can control the size a bit, open up a view and neaten up the tree's form.

Planting notes. Young trees grow surprisingly fast. You can start with nursery plants, available in containers from gallon size to boxes 10 feet square. Choose single-trunk or multiple-trunk shapes. To create a naturalistic grove, plant several trees. Locate live oak away from a lawn or other spot that gets heavy summer watering, and plant it in full sun.

Make sure the drainage is good. Generally there's no need to amend the planting soil. You'll need to water the tree regularly, even in the summer, for the first few years. Provide a sturdy stake. If you live around wildlife, protect young tree trunks from deer, rabbits and other critters.

The main pest is the oak moth caterpillar, which can shred a tree every now and then. If you see caterpillars falling out of the tree or descending on silk webs, or if you notice signs of defoliation, call a professional tree service. Spraying for oak moths is a major project.

The most fearsome threat to native oaks is sudden oak death, a pathogen that has been killing Northern California’s coast live oaks and related species. (Not all native oaks are susceptible.) The pathogen’s spores spread during the rainy season, and leaves of afflicted trees wilt and die; sap exudes from the trunk and branches. If you notice signs of disease, call a professional arborist.

How to grow an oak from an acorn. It’s not hard to start an oak tree from an acorn directly in the ground. Your enemies will be the usual suspects: birds and squirrels. In fall or winter, start with a healthy (no insect holes) fallen acorn.

In a sunny spot, dig a planting hole 6 inches deep and 6 inches wide. Refill the hole with the excavated soil and bury the acorn sideways an inch deep. The acorn should sprout by spring. Water the soil and keep it moist through the first summer at least.

To improve your chances of success, plant at least several acorns a foot or two apart. Thin the survivors to leave just one or two. Create a screen of wire mesh to protect the sprouting seedlings from hungry creatures.

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