Seasonal Tree Care Calendar for Bay Area Homeowners

The ideal pruning window for most Bay Area trees is December through February, when deciduous trees are dormant and the risk of disease transmission is lowest. Avoid pruning oaks between April and August when bark beetles are most active. Dead or hazardous branches can be removed any time of year.

October through early December is the best planting window. Trees planted in fall benefit from winter rains to establish roots before summer heat. March through April is a secondary window, but you'll need to commit to regular watering through the first summer.

Fire season typically runs from late May through November, with peak risk from September through November when vegetation is driest and offshore winds are strongest. Defensible space work should be completed by May 1 to meet Cal Fire requirements.

Newly planted trees need deep watering every 5-7 days during summer. Established native oaks generally need no supplemental water — in fact, summer irrigation around the root zone can cause root rot. Non-native species may benefit from deep watering every 2-3 weeks during extended dry periods.

Inspect your trees after every significant wind or rain event, especially during the November-through-March storm season. Look for hanging branches, new leans, cracked limbs, lifted root plates, and soil heaving near the trunk base. If you spot structural damage, contact a certified arborist before the next storm.

Permits for pruning depend on your city's ordinance. Most Bay Area cities allow routine pruning of up to 20-25% of the crown without a permit, but some cities like Palo Alto require approval for pruning heritage trees above certain sizes. Use our Permit Checker tool to look up your specific city's rules.

The most damaging pests in the Bay Area include polyphagous shot hole borer (attacking sycamores, maples, and oaks), sudden oak death (affecting coast live oaks and tanoaks), and pitch canker on Monterey pines. Monitor for unusual bark bleeding, sawdust-like frass, branch dieback, or canopy thinning.

Late winter and early spring (January through March) tend to offer the best availability and pricing, as demand is lower outside of storm emergencies. Avoid scheduling routine work during peak fire season (August through October) when arborists are busiest with defensible space projects.

Start storm preparation in September or October. Remove dead and weakly attached branches, reduce sail effect on top-heavy trees, and inspect for signs of root rot or structural weakness. Prioritize trees near structures, power lines, and walkways. A professional tree risk assessment is recommended for any mature tree within falling distance of your home.

Spring planting (March through April) is fine, but you'll need to water consistently through the first summer — typically deep soaking every 5-7 days. Fall planting is preferred because winter rains do most of the work. Avoid planting after May, as the dry season makes establishment much harder and mortality rates increase.

Mushrooms at the base of a tree usually indicate wood decay in the roots or lower trunk. This can be a serious structural concern, especially for large trees near buildings. Do not remove the mushrooms — photograph them and contact a certified arborist for a risk assessment. Some fungi like honey fungus or sulfur shelf can compromise a tree's stability.

Most established Bay Area trees do not need fertilization if they receive adequate mulching. If a soil test indicates deficiency, apply slow-release fertilizer in late February or early March as trees come out of dormancy. Never fertilize a stressed or drought-damaged tree — fix the water issue first. Over-fertilization pushes fast, weak growth that's more vulnerable to pests.