Answer: Oak trees create tough environments that demand plants capable of tolerating dry shade, slightly acidic soil, and falling leaf litter. Native oaks must have dry soil in summer or they risk developing oak root fungus.
The most at-risk species include coast live oak (Quercus agrifolia), canyon oak (Q. chrysolepis), mesa oak (Q. engelmannii), Oregon white oak (Q. garryana), California black oak (Q. kelloggii), valley oak (Q. 1obata), and interior live oak (Q. wislizenii).
To reduce the spread of oak root fungus, underplant the tree with droughttolerant flowering plants and ground covers. Experts recommend that you keep all plantings 4 to 6 feet away from the oak's trunk. You'll need to give the plants a little extra water their first summer, but after that, they should do well on what nature supplies. When you do irrigate, don't water within 4 feet of the oak's trunk or allow standing water to collect there.
When choosing plants for under oaks you must first determine if it is shaded, or will receive lots of afternoon sun. I prefer using drought resistant plants, and water only enough to keep the plant healthy. In sunny to lightly shaded situations some plants to consider are, Manzanita (Arctostaphylos), Toyon (Heteromeles), Strawberry Tree (Arbutus unedo). In shaded to lightly shaded areas try Winter Daphne (Daphne odora), Sweet Box (Sarcococca) or Nandina (Nandina domestica). Trailing Manzanita (Arctostaphylos uva-ursi), Arron?s Beard (Hypericum calycinum), and some Rockrose (Cistus) make good groundcovers in sunny or lightly shaded areas.
Wildflowers planted under oaks are also an interesting solution. The wildflowers will sprout in the late winter, and bloom through the spring. With no irrigation they will turn brown and die at the beginning of summer. This is the time to mow the brown stems and flowers down. The seed of the wildflowers will have spread throughout the area laying dormant until the rain return next winter. No extra water necessary for this solution. Plant the wildflowers in the fall just before the rains begin.
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