What Causes the Yellowing of Syringa Leaves?
In the midst of summer, gardeners can't help but feel anxious when they discover that the carefully nurtured syringa leaves are gradually losing their lush green and developing sickly yellow spots. As a traditional flowering plant with both ornamental and medicinal values, yellowing syringa leaves may indicate multiple growth crises. This article will systematically analyze the causes of yellow leaves and provide targeted solutions.
Three Core Causes of Yellowing Syringa Leaves
Seasonal Metabolic Changes
The unique physiological mechanism of woody plants causes syringa to initiate self-protection procedures in the late autumn. As the temperature drops below 10℃, the chlorophyll in the leaves gradually decomposes, and carotenoids become visible, forming a natural yellowing. This is a normal phenomenon for the plant to store energy for winter, and the yellow leaves will naturally fall off as the temperature decreases.
Iron Deficiency Syndrome
When the soil pH is greater than 7.5, iron forms insoluble compounds. This is particularly evident in the calcareous soil areas of the north. When the roots cannot absorb sufficient iron ions, the new leaves first show reticulate yellowing, followed by the whole plant exhibiting chlorosis symptoms. Continuous iron deficiency can lead to a 40%-60% decrease in photosynthetic efficiency, directly affecting flower bud differentiation.
Root Development Disorder
Heavy and compacted soil or waterlogged conditions can reduce root oxygen exchange by more than 75%, leading to the necrosis of fine roots and hindering the transport of nutrients. This type of yellowing is often accompanied by symptoms such as leaf curling and leaf edge scorching, requiring timely intervention to prevent the death of the entire plant.
Four Steps to Save Yellowing Syringa
Soil Structure Improvement Technique
For potted plants, it is recommended to change the substrate every spring, mixing in the ratio of decomposed leaf soil: peat soil: coarse sand = 5:3:2. For ground planting, mix 10kg of decomposed pine needles per square meter and配合 set up 30cm drainage ditches to increase the soil porosity to about 45%.
Precise Iron Supplement Plan
Use EDTA chelated iron, spraying the back of the leaves at a ratio of 1:1000 every half month. In combination with root application of a mixture of ferrous sulfate (3g/plant) and citric acid (1g/plant), the absorption rate of iron can be increased to 90%. Be careful not to mix with alkaline fertilizers.
Ecological Regulation Techniques
Collect rainwater or let tap water stand for 2 days before watering, adding 5ml of vinegar per 10L of water to adjust the pH monthly. Laying a 5cm thick layer of pine bark can not only retain moisture but also slowly release organic acids, continuously improving the rhizosphere microenvironment.
Root Revival Management
For waterlogged yellowing plants, it is necessary to promptly remove the pot and prune the decayed roots, disinfect with a 1000-fold solution of potassium permanganate, and then replant in new soil. Maintain scattered light for the first two weeks, and gradually increase light exposure after new roots have sprouted.
Through systematic diagnosis and scientific intervention, about 85% of yellowing syringa plants can recover within 30 days. It is recommended to establish a maintenance log, recording each fertilization and watering and the plant's response, gradually mastering the precise maintenance rhythm to ensure that the purple inflorescences bloom year after year.