Bay Area Care Calendar

Seasonal Care Guide

Month-by-month bonsai care written specifically for Northern California's climate — dry hot summers, mild rainy winters, and foggy Bay Area springs.

🌸 Spring ☀️ Summer 🍂 Autumn ❄️ Winter 📅 Monthly 🛠 Techniques

March · April · May

🌸 Spring

Spring is the most critical and exciting season in bonsai. New growth signals the end of dormancy and opens the window for repotting, first fertilizing, and early styling work. In NorCal, spring often arrives earlier than in Japan — watch your trees, not the calendar.

March

  • Inspect all trees for winter damage — remove dead wood
  • Begin repotting deciduous trees as buds begin to swell
  • Apply first balanced fertilizer (NPK 10-10-10) as growth begins
  • Move indoor trees outdoors once nights consistently above 50°F
  • Clean and sharpen tools before the busy season

April

  • Repot junipers and most conifers before budding
  • Begin wiring deciduous trees before leaf fully unfurls
  • First pinch on Black Pine as candles extend but before needles open
  • Watch closely for aphids on new maple growth
  • Switch to nitrogen-heavy fertilizer to push new growth

May

  • Harden off repotted trees — transition from shade to sun
  • Prune back vigorous shoots on established trees
  • Begin defoliation of deciduous trees for leaf reduction
  • Increase watering frequency as temperatures rise
  • Apply diluted liquid fertilizer every 2 weeks
Bonsai in spring
Spring repotting season — Bay Area Bonsai

NorCal Spring Notes

Bay Area springs can be unpredictable. Marine layer clouds moderate temperatures, which is excellent for recently repotted trees. Our springs are typically drier and warmer than Japanese growing climates, so watch watering carefully after repotting.

Late frosts (rare but possible through March in Santa Clara Valley) can damage emerging growth on Maples. Keep a frost cloth on hand until mid-April.

Bonsai in summer
Summer — shade cloth in position for Maple

Summer Heat Management

Santa Clara heat spikes (100°F+ in July–August) are the #1 killer of bonsai in our area. Shade cloth and twice-daily watering are essential. Black Pine candle work must happen in mid-July regardless of heat.

June · July · August

☀️ Summer

Bay Area summers are hot and dry — especially in the South Bay. Daily watering is non-negotiable, and afternoon shade protection for delicate species can mean the difference between a thriving tree and a dead one.

June

  • Install shade cloth (50%) for Japanese Maple and beech
  • Water daily — check morning and evening in heat
  • Prune and pinch to slow vigorous summer growth
  • Begin transition to balanced fertilizer from nitrogen

July — Black Pine Month

  • Candle prune Black Pines mid-July (when candles have extended)
  • Twice-daily watering during heat waves — early AM and evening
  • Do not repot — roots are actively growing and heat stress is high
  • Watch for spider mites on dry, dusty foliage

August

  • Reduce fertilizer strength — trees begin slowing growth
  • Check all wires — remove anything biting into thickening bark
  • Begin planning autumn repotting for conifers
  • Take stock photos of summer growth for comparison

September · October · November

🍂 Autumn

Autumn is the photographer's season — and the second major repotting window. NorCal fall colors peak in October and November, and the arrival of rains signals time for conifer repotting.

Sep

First Rains Arrive

  • Repot junipers and pines as fall rains begin
  • Switch to phosphorus-rich fertilizer for hardening
  • Begin preparation of winter protection materials
  • Remove shade cloth as temperatures moderate
Oct

Peak Fall Color

  • Photograph your collection at peak color
  • Defoliate deciduous trees to study winter silhouette
  • Begin strategic wiring of dormant deciduous trees
  • Order akadama, pumice for spring repotting
Nov

Dormancy Begins

  • Move tropicals indoors before first frost warning
  • Final check — remove all wire from deciduous trees
  • Light application of fertilizer before growth stops
  • Prepare cold frames for protection if needed

December · January · February

❄️ Winter

NorCal winters are mild compared to most growing climates — Santa Clara rarely drops below 28°F. This actually creates some unique challenges: species that need cold dormancy may not get enough chill hours, and over-watering in rainy weather is a common mistake.

Essential Winter Tasks

  • Protect tropicals (Ficus, Serissa) from cold — bring inside below 45°F
  • Reduce watering to only when soil has dried — check before each session
  • Study winter silhouette of deciduous trees for spring styling planning
  • Deep clean and sharpen all tools — oil blades against rust
  • Order supplies for spring: akadama, wire, pots, fertilizer
  • Keep conifers outdoors for dormancy — they need the cold
  • Repot early spring bloomers (Plum, Apricot) after flowering

Winter Frost Thresholds

< 28°F (-2°C) All trees at risk. Cover or move inside immediately.
28–35°F Protect tropicals and sub-tropicals. Junipers fine.
35–45°F Move tropical/indoor species to shelter.
> 45°F All outdoor hardy species fine outdoors.

📅 Monthly Quick Reference

Month Focus Watering Fertilizer Repotting OK?
Jan Planning, winter protection Low — check weekly None Plum after bloom
Feb Tool prep, early deciduous repot Low–medium Start light Early deciduous
Mar Repotting season opens Medium, increase Begin fertilizing Deciduous, broadleaf
Apr Peak repotting, first styling Medium–high Nitrogen-heavy Conifers, most species
May Pinching, defoliation begins High Regular Junipers, pines OK
Jun Shade management, pruning Daily Balanced Only urgent cases
Jul Black Pine candles, heat management Daily, twice if 90°F+ Reduce No
Aug Remove wires, plan autumn High — daily Reduce further No
Sep First rains, conifer repotting Moderate — watch rain Phosphorus-heavy Conifers excellent
Oct Photography, wiring, defoliation Moderate Reduce Conifers fine
Nov Dormancy prep Low–medium Stop or minimal Avoid
Dec Rest, study, plan Low — weekly checks None Avoid