What Causes the Yellowing of Osmanthus Leaves
Osmanthus, as a common ornamental plant in gardens, the issue of yellowing leaves has been困扰ing many growers. The yellowing phenomenon often indicates that there are oversights in the maintenance process, and it is necessary to systematically investigate the causes from three dimensions: soil condition, water management, and environmental adaptation.
Abnormal Root Environment
Imbalance of Dryness and Moisture Leading to Yellow Leaves
When the moisture content of the potting soil is less than 40%, the capillary roots lose their water absorption function due to dehydration, causing the edges of old leaves to scorch and the veins to turn green. It is recommended to use the bamboo stake method: insert a bamboo stake into the potting soil to a depth of 5cm, and if there is no moisture attached after pulling it out, water immediately.
Waterlogging and Root Rot Crisis
Waterlogging in ceramic pots for more than 12 hours can trigger anaerobic respiration, causing reddish-brown rot spots on the roots. Use the double-layer water control method: place a 3cm layer of ceramic stones at the bottom of the pot, and combine pine needle soil with coarse river sand (2:1) mixed substrate to improve drainage efficiency by over 35%.
Disorders of Soil Physicochemical Properties
PH Imbalance
When the soil pH value is greater than 7.2, iron elements are fixed, causing new leaves to yellow between the veins. Applying 800 times liquid sulfuric acid iron monthly, combined with decomposed pine needle compost, can maintain the ideal pH range of 5.5-6.5.
Salinization Accumulation
Long-term use of hard water irrigation can form white salt crystals, causing physiological drought. It is recommended to collect rainwater for irrigation, or let tap water stand for 48 hours before diluting it with 0.1% citric acid.
Systematic Maintenance Plan
In the spring germination period, apply slow-release fertilizer with nitrogen, phosphorus, and potassium (15-10-12), combined with foliar spraying of chelated iron and brassinolide. In the hot summer period, set up a 50% shade net, and cover the potting soil surface with 5cm of pine scales in winter for insulation. Conduct potting and root pruning around the time of Jingzhe every year, removing blackish-brown diseased roots and replacing 1/3 of the substrate.
By establishing a soil moisture monitoring log and combining regular pH testing, the root microenvironment can be accurately controlled. When the bottom leaves turn yellow, an immediate comprehensive diagnosis should be made and step-by-step treatment measures should be taken, usually 2-3 growth cycles can restore the tree's vitality.