The Reasons and Solutions for the Yellowing of crabapple Leaves
In the midsummer season, many flower enthusiasts notice that the leaves of their crabapple plants start to turn yellow, and the once glossy green leaves gradually lose their vitality. As a typical foliage and flowering plant, crabapple is particularly sensitive to changes in the growing environment. When yellowing occurs, it often means that the plant is sending out a distress signal. This article will focus on three common causes and provide professional solutions.
Excessive Light Leading to Leaf Burn
Formation Mechanism of Yellow Leaves
crabapple is a semi-shaded plant. From late spring to early autumn, when the midday light intensity exceeds 30,000 lux, the leaves will activate their self-protection mechanism. The chloroplast structure is damaged, the proportion of xanthophyll increases, irregular yellow spots appear on the sun-exposed side, and severe cases are accompanied by leaf margin curling.
Scientific Sunshade Solution
Upon discovering yellow leaves, damaged leaves should be immediately pruned, using a gardening shear to make a 45-degree diagonal cut at the base of the petiole. Move the plant to an east-facing balcony, or use a 40% shade net. It is recommended to provide shade from 10:00 to 15:00 daily, maintaining an environmental humidity of around 60%, and new buds can sprout in about 2 weeks.
Root Waterlogging Leading to Metabolic Disorders
Characteristics of Root Rot Identification
If there is obvious water seepage when pressing the potting soil with a finger, it indicates that the soil moisture content is excessive. At this point, the roots have already developed hypoxic necrosis, with typical symptoms being uniform yellowing of the old leaves from the bottom up, softening at the base of the petiole, and the entire plant may collapse in severe cases.
Emergency Potting Steps
Remove the plant from the pot and cut off the brown decayed roots, retaining white new roots with a diameter of 2mm or more. Soak in a 1000-fold solution of potassium permanganate for 30 minutes, then replace with a slightly acidic substrate containing 30% perlite (pH 5.5-6.5). After repotting, place the plant in a well-ventilated, shady area, and only spray water on the leaves for the first 3 days.
Excessive Fertilizer Concentration Burning Roots
Development Process of Fertilizer Burn
Excessive fertilization can lead to a soil EC (electrical conductivity) value exceeding 2.5mS/cm, causing the separation of cell walls in root cells. Initially, the leaf tips show a burnt yellowing, followed by radial yellow spots between the veins, and eventually the entire leaf falls off.
Emergency Response Techniques
Immediately perform a continuous 30-minute immersion pot rinse, repeating 3 times to reduce soil salinity. Alternatively, when changing the soil, mix in 5% activated carbon granules to absorb remaining fertilizer. During the recovery period, switch to applying 0.1% potassium dihydrogen phosphate foliar fertilizer, spraying once every 10 days.
By addressing the above three dimensions with targeted treatments, combined with measures such as testing the soil pH monthly, regularly rotating the pot to ensure uniform light exposure, and adopting a "water when dry, stop when wet" watering principle, effectively prevent the recurrence of yellowing in crabapple leaves. When plants show abnormal growth, it is recommended to check environmental parameters first, as timely intervention can significantly increase the success rate of treatment.