What to Do When Hydrangea Leaves Turn Yellow
Summer should be the prime time for hydrangeas to bloom, but many gardeners find that their plants are experiencing yellowing leaves and crispy leaf edges. As a typical acid-loving plant, hydrangeas have special requirements for their growing environment. This article will address the four main causes of yellowing leaves, combined with 20 years of gardening experience, to provide you with a systematic solution.
Soil pH Control
Root Cause of Yellow Leaves: Soil Alkalinity
Hydrangeas are acidophilic plants, and when the soil pH is greater than 6.5, the availability of iron decreases, hindering the synthesis of chlorophyll. Typical symptoms include the loss of green between the veins of new leaves and the browning of the edges of old leaves. According to research by Nanjing Agricultural University, acidic soil (pH 5.2-5.8) can increase iron absorption by 83%.
Improvement Plan: Triple Acidification Method
It is recommended to alternate monthly between ① 0.2% ferrous sulfate + citric acid solution (1:2000), ② potassium dihydrogen phosphate solution (1:1500), and ③ diluted rice vinegar (1:250). Add sulfur powder (0.5g per liter of soil) when repotting, and use alum fertilizer water (every 15 days) to maintain soil acidity for 2-3 years.
Light Intensity Management
Yellow Leaf Symptoms: Light Damage and Light Deficiency
From late spring to early autumn, a shading net (50-70% light blocking rate) should be set up to avoid direct sunlight from 10:00 to 15:00. If brown sunburn spots appear, immediately move the plant to a diffused light environment and spray 0.01% brassinolactone for repair. In winter, ensure 4 hours of direct sunlight a day, and maintain a distance of 30cm when using grow lights.
Precise Water and Fertilizer Control
Irrigation Quantity Standard
What to Do When Hydrangeaingea Leaves Turn Yellow
Use the "Two-Finger Test": if the soil 2cm below the surface is dry, it's time to water. In the summer, when evaporation is high, spray the leaves with water early and late (avoiding the flower buds). For ground-planted plants, create a 10cm high ridge to prevent waterlogging. In case of sudden yellowing leaves, water with seaweed extract (1:1500) to promote root repair.
Fertilization Schedule
In the growing season (March to June), use a balanced water-soluble fertilizer (20-20-20), switch to high-phosphorus fertilizer (10-30-20) during the budding stage, and apply decomposed sheep manure (200g/plant) after flowering. Pay attention to applying thin fertilizers frequently, keeping the EC value between 1.2-1.8mS/cm to avoid fertilizer burn and yellow leaves.
Root Health Management
Every two years, change the growing medium, using a mix of peat soil: leaf mold soil: perlite = 5:3:2. Regularly check the crown area, and if browning is found, apply hymexazole 2000 times solution to the roots. Through the above systematic care, the leaves of the hydrangea can return to their green color and bloom beautifully again.