Bonsai Calendar: The Month-by-Month Guide

Introduction: Following Nature's Rhythm

The art of bonsai is an ongoing dialogue with nature. To succeed, it is not enough to know the techniques; it is essential to understand when to apply them. Every task, from pruning to repotting, has its perfect time, determined by the plant's life cycle and the changing seasons. Acting at the right time means working with the bonsai, not against it, ensuring its health, vigor, and beauty.

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This bonsai grower's calendar was created to be your definitive guide, your monthly reminder so you never miss the right time. We have organized it simply and visually, with clear checklists for every month, removing any doubt about "what to do and when." Bookmark this page: it will become your inseparable companion on this wonderful journey.

Spring: The Great Awakening

In spring, the busiest season for bonsai growers, the main tasks take place: in March, repotting, structural pruning of deciduous trees, and the first fertilizing; in April, pinching new shoots, more frequent watering, and preventive treatments; in May, regular fertilizing, pruning flowering bonsai after flowering, and protecting them from midday sun.

Spring is the busiest and most delicate season for a bonsai grower. It is a time of rebirth, when the foundations are laid for the entire growing season.

March: The Month of Repotting and Pruning

• Repotting: This is the ideal time to repot most species (deciduous and coniferous). The roots are ready to colonize the new substrate. Do not repot plants that are already flowering.
• Structural Pruning: For deciduous trees, before the buds open, this is the time for drastic structural pruning to correct flaws and establish the silhouette.
• First Fertilizing: Toward the end of the month, when the new buds begin to swell, apply the first dose of light, balanced fertilizer.

April: Managing New Growth

• Pinching: New shoots grow vigorously. It is essential to "pinch" (shorten) new shoots to maintain the shape and encourage the growth of a dense, branching canopy.
• Watering: Increase watering frequency. The soil should remain moist, but never waterlogged.
• Preventive Treatments: As temperatures rise, it's the right time for preventive treatment against aphids and fungi.

May: Peak Vegetative Activity

• Regular Fertilizing: Follow your fertilizing plan in full, applying liquid fertilizer every 15-20 days or slow-release solid fertilizer every 30-40 days.
• Post-Flowering Pruning: For flowering bonsai that have finished blooming (such as azaleas (Rhododendron)), this is the time to prune so as not to compromise next year's flowering.
• Exposure: Watch out for the first very hot days. Make sure your more delicate bonsai are not exposed to the scorching midday sun.

Summer: Energy and Hydration

In summer, water is the top priority: from June to August, check your bonsai every day, morning and evening, and water them twice a day in intense heat. Move more sensitive species to partial shade, inspect plants for spider mites and scale insects, and slightly reduce fertilizer doses.

Summer is the season for consolidation. Growth slows slightly, and proper water management becomes the top priority.

June, July, August: Water Is Life

• Daily Watering: Check your bonsai every day, morning and evening. In intense heat, they may need watering twice a day. Water thoroughly until water runs out of the drainage holes.
• Sun Protection: Move more sensitive bonsai (maples, Acer; beeches, Fagus) to a partially shaded spot to prevent leaf scorch.
• Pest Control: Regularly inspect plants to identify early infestations of red spider mites or scale insects, which are encouraged by hot, dry weather.
• Fertilizing: Continue fertilizing, perhaps slightly reducing the dose during periods of intense heat (above 30-32°C).

Autumn: Preparing for Dormancy

In autumn, bonsai prepare for dormancy: in September and October, use a fertilizer low in nitrogen and rich in phosphorus and potassium, do light maintenance pruning, and gradually reduce watering; in November, remove dry leaves from the soil and prepare winter shelter, such as a cold greenhouse or protective covers.

Autumn is a second spring for many plants. Colors brighten, and the plant stores energy for winter.

September, October: Colors and Nourishment

• Fall Fertilizing: This is a crucial time. Use a fertilizer low in nitrogen (N) and rich in phosphorus (P) and potassium (K). This helps new branches lignify and prepares the plant for the cold.
• Light Pruning: Maintenance and thinning pruning can be done to let more light into the canopy.
• Reducing Watering: As temperatures drop, gradually reduce watering frequency.

November: The Start of Dormancy

• Cleaning: Remove dry leaves from the soil surface to prevent fungal diseases.
• Preparing for Frost: Start thinking about where to shelter your bonsai during winter. Prepare the cold greenhouse or protective covers.

Winter: The Warrior's Rest

In winter, bonsai are dormant, and the bonsai grower's job is to protect them without disturbing them: from December to February, shelter them in a cold greenhouse or against a wall, water only when the soil is dry and during the warmest hours; meanwhile, study the structure of leafless deciduous trees, and you can apply dormant oil treatments.

Winter is the dormant period, essential for the plant's health and vigor. Our job is to protect it and leave it undisturbed.

December, January, February: Protection and Patience

• Frost Protection: Move bonsai to a cold greenhouse or place them against a wall. Wrap the pots with frost cloth if temperatures stay below freezing for many days.
• Minimal Watering: Water only when the soil is really dry, during the warmest hours of the day, to prevent the water from freezing in the pot.
• Structural Pruning: On deciduous trees without leaves, this is the best time to study the structure and plan formative pruning to be carried out in late February/early March.
• Winter Treatments: You can apply dormant oil or lime sulfur treatments to eliminate pest eggs and fungal spores.

The Beginner's Alternative: A Simplified Calendar

If you're just starting out, don't be intimidated! Focus on these 4 key times: 1. Early Spring (March): Repot if necessary and start fertilizing. 2. Late Spring (May): Start pinching new shoots to thicken the canopy. 3. Summer (June-August): Check the water EVERY day. 4. Autumn (September-October): Use an autumn fertilizer and get ready to protect the plant from the cold.

Frequently Asked Questions (FAQ)

Can I prune a bonsai in summer? You can only do light pinching and maintenance pruning. Avoid drastic pruning of the main branches, as it would weaken the plant too much during a stressful period.

When should I stop fertilizing in autumn? The last application is generally made between late October and early November, before the first frosts arrive.

What does "pinching" mean? It means shortening new shoots once they have grown a little, usually leaving only the first two or three leaves. This encourages the plant to produce new shoots farther back, creating a denser, more compact canopy.

Does my indoor bonsai (e.g., Ficus) follow the same schedule? Generally, yes, but less noticeably. Since it is kept in a temperature-controlled environment, it does not go into true dormancy. Fertilizing should only be reduced (not stopped) in winter, and watering should be adjusted based on how dry the soil is, which will differ from that of an outdoor plant.