Mystery Tree in Southern California: Ficus or Succulent?

The description—a single, sometimes curved trunk with a dense crown of long, thin, semi-tough green leaves sprouting from a central point, resembling a porcupine on a pole—suggests a few possibilities common in Southern California:

• Ficus species (e.g., Ficus microcarpa, Ficus benjamina): many have a single trunk and a dense canopy. Breaking a leaf or stem releases white milky latex.
• Succulent trees like Euphorbia or Beaucarnea (ponytail palm): also have a swollen base and strappy leaves.
• Dracaena or Yucca species: rosettes of long, narrow leaves atop a trunk.

Because the genus Ficus is huge and diverse, compare photos online. A local nursery or garden center in Southern California can identify it instantly—it's likely a common landscape tree there. If it bleeds white sap when a leaf is snapped, it's almost certainly a Ficus.