What to Do When Bougainvillea Loses Its Leaves in Winter
In the cold winter months, discovering that the bougainvillea leaves have all fallen, leaving bare branches, can be disheartening. As a typical southern flower, bougainvillea is sensitive to low temperatures, and it is highly susceptible to frostbite and leaf drop when the ambient temperature falls below 10°C. However, the plant is not entirely dead, and it can still revive with scientific treatment.
I. Emergency Treatment Plan for Bougainvillea Frostbite
1. Pruning Branches and Diagnosing Roots
First, use a sterilized scissor to cut off the dried tender branches, retaining the lignified part of the main stem. Focus on observing the cross-section of the branches: if clear sap seeps out, it indicates survival, while a dry cross-section requires further pruning. Then, gently prod the surface layer of potting soil with a bamboo skewer to check the color distribution of the roots: if more than 60% of the roots are white, there is no need to repot; if more than 40% of the roots are black and decayed, root pruning and repotting are necessary.
2. Key Points for Repotting and Seedling Recovery
When repotting, retain 1/3 of the original soil, cut off the blackened decayed roots, and soak them in carbendazim solution for 30 minutes. Choose a red pottery pot with a mixture of decomposed leaf soil and perlite (3:1) as the growing medium. After repotting, water the roots along the pot wall and place the plant in a scattered light environment of 18-22°C for 15 days.
II. Environmental Regulation for Promoting Bud Growth and Recovery
1. Precise Temperature and Humidity Control
Maintain a day-night temperature difference within 8°C (22-25°C during the day and 14-16°C at night), with an air humidity of 50%-60% being ideal. You can use a transparent plastic bag to create a mini greenhouse and vent for 2 hours daily to prevent mold.
2. Nutrient Supplement Plan
After new buds emerge, spray a 0.1% mixture of potassium dihydrogen phosphate and seaweed extract weekly, combined with shallowly burying decomposed sheep manure (50g per pot) around the edge of the pot. Be cautious of excessive nitrogen fertilizer, which can cause excessive growth.
III. Special Winter Maintenance Protection
In the north, move the plant indoors before the first frost and use a plant grow light for 4 hours daily. Covering the surface of the potting soil with 5cm of pine bark can raise the ground temperature by 3-5°C. In extreme low temperatures, use double-layer insulation: an inner layer of woven bags and an outer layer of non-woven fabric.
Through systematic treatment, new buds can be seen emerging after about 30-45 days. The following spring, combined with heavy pruning for shaping, the bougainvillea can recover its vigorous growth. In daily maintenance, pay attention to temperature warnings; if the nighttime temperature consistently drops below 12°C, it is necessary to initiate cold protection measures.