Spring and Your Bonsai: Essential Care Guide

Spring has arrived, and with it, the busiest time for our bonsai. After the winter dormancy, the trees awaken with an explosion of life and energy. It is a crucial period where our work will lay the foundation for healthy, strong, and beautiful trees throughout the year.

Here is a guide with the key tasks you should perform, based on some important notes for this season.

1. Repotting: Renewing Energy

Spring is, par excellence, the repotting season for most species. The goal is to renew the depleted substrate and prune the roots to encourage a finer, more efficient root system.

• When to repot? The ideal time for deciduous trees is just as the buds begin to swell, but before they open. For conifers (pines, junipers), it is usually a bit later, well into spring.
• An important exception: As you rightly point out, evergreen species of tropical or subtropical origin (like Ficus, Olive trees in very mild climates, etc.) often benefit from a later repotting, in late spring or early summer, coinciding with their peak growth.

2. Protection Against Late Frosts

The new shoots of deciduous trees are extremely tender and vulnerable. A late frost, after the tree has already budded, can be fatal to the new growth and severely delay its development.

• Action: Check the weather forecast. If frost is predicted and your trees have already started to move sap, protect them overnight. An eave, a cold greenhouse, or even moving them into the garage until the next morning will be enough to save those precious shoots.

3. Preventive Treatments: Better Safe Than Sorry

The end of winter and the beginning of spring is the perfect time for preventive phytosanitary treatments. With the humidity and rising temperatures, fungi can awaken.

• Fungicide: Applying a copper-based fungicide, such as copper oxychloride, on the trunk and branches (before they bud) helps to eliminate fungal spores that may have overwintered on the bark. It is a “spring cleaning” that can prevent many future problems.

4. Watering: Adapting to the Awakening

The watering routine changes drastically with the arrival of spring.

• Transition: While a dormant tree in winter barely needed water (perhaps once a week or less), the situation is now the opposite. As soon as the tree activates and begins to bud, its water needs skyrocket.
• Increased frequency: Be prepared to increase the watering frequency. Depending on the substrate, species, and climate, you will likely need to switch to almost daily watering. The golden rule remains the same: check the substrate’s moisture and water thoroughly when it begins to dry out.

5. Fertilizing: The Fuel for Growth

Fertilizing is essential, but doing it at the right time is key for compact and balanced development.

• Patience: Don’t rush! Wait for the tree to start budding and for the first wave of growth to settle. If you fertilize just as the buds open, you risk the shoots bolting, creating very long internodes and weak, uncontrolled growth.
• The signal: A good time to start with a balanced fertilizer is when the first leaves have fully expanded and have taken on a more mature green tone. From then on, follow a regular fertilizing regimen throughout the growing season.

By following these steps, you will prepare your bonsai to make the most of spring’s energy, resulting in vigorous, healthy, and controlled growth. Happy growing season!