5 Common Mistakes to Avoid When Protecting Bonsai in Greenhouses During Winter

5 Common Mistakes to Avoid When Protecting Bonsai in Greenhouses During Winter

Using a greenhouse to protect your bonsai may seem like the perfect solution for winter

but there are some common mistakes that could compromise the health of your plants. Here's how to avoid them and ensure your bonsai receives proper care.

1. Ignoring Temperature Fluctuations

Small, unventilated greenhouses can quickly reach high temperatures on sunny days, even in winter. Without proper ventilation, the temperature can easily exceed 30°C, causing heat stress to the plant. This rapid increase in heat can trigger premature growth, weakening the bonsai and making it more vulnerable to future damage. Regularly monitor the temperature inside the greenhouse and ensure that vents are open or fans are installed to prevent these fluctuations.

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2. Lack of Ventilation and Risk of Fungal Diseases

Poor ventilation creates a humid, stagnant environment, ideal for the development of fungal diseases like botrytis (grey mold), which attacks the leaves, branches, and roots of bonsai. To prevent the spread of diseases, it is essential to keep the air moving inside the greenhouse. You can install a fan to improve air circulation or open the greenhouse regularly on milder days. If you notice signs of fungal infection, such as grey spots and decaying leaves, apply an appropriate fungicide and remove the infected parts to stop the spread.

3. Insufficient Light for Evergreen Species

Evergreen species like junipers and pines need light throughout the winter. It's important not to overcrowd the greenhouse with plants and to maintain sufficient distance between them. Avoid placing bonsai under shelves or in areas that are too shaded just to save space. The lack of light can weaken the plant, causing the branches to stretch and grow unevenly. Moreover, during the spring awakening, plants placed too close together can lose parts of their foliage due to competition for light. Distribute your bonsai well within the greenhouse to ensure healthy growth.

4. Not Monitoring Soil Moisture

Although the greenhouse offers protection from cold and rain, the soil moisture must be carefully monitored. Excess moisture in the soil, especially in winter, can lead to root rot, which is particularly dangerous for bonsai. Ensure the substrate is well-draining, and water only when the soil starts to dry out slightly. Avoid directly wetting the leaves and encourage proper air circulation to reduce humidity.

5. Underestimating the Risk of Pests

Even in a greenhouse, pests can survive and thrive. Aphids, scale insects, and spider mites are just some of the pests that might trouble your bonsai, taking advantage of the sheltered environment. Perform regular checks, inspecting both the top and bottom of the leaves. Treat infestations with insecticidal soaps or natural oils to prevent damage. Keep the greenhouse clean and free of fallen leaves, which can become a refuge for pests.

 

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Conclusion

Protecting bonsai in a greenhouse is an effective strategy to help them survive the winter, but it's essential to manage temperature, ventilation, and lighting properly to avoid problems. Make sure the plants get enough light, the air circulates, and moisture is controlled, and your bonsai will be ready to bloom with strength in the spring.

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