aloe_marlothii
winter_shady_garden
These pictures show two plantings under oak trees, the one on the left receives morning sun all year round, whereas the one on the right only gets morning sun in winter when the neighboring sycamore loses its leaves.
The characterful plants on the left never need maintenance and, after a couple of years, will virtually never need water. These are fire safe plants.
Bromeliads and many succulents (shown on the right) do well planted under California live oaks, and because they are drought tolerant and very shallow rooted they do not affect the soil negatively.