Reasons and Solutions for Yellowing Leaves on Roses
Roses, as common ornamental flowers in gardens and balconies, have been plagued by yellowing leaves for many growers. Leaf discoloration not only affects the ornamental value but also serves as a distress signal from the plant. This article will systematically analyze four typical causes of yellowing leaves and provide scientific coping strategies.
I. Nutritional Imbalance Causes Yellowing Leaves
Characteristics of Iron Deficiency Yellow Leaves
In greenhouse cultivation, 70% of yellow leaves in roses are caused by iron deficiency. Typical symptoms include new leaves turning a lemon yellow while the veins remain green, forming a net-like pattern, and in severe cases, the entire leaf yellows with crispy leaf edges.
Precise Iron Supplement Plan
Use an organic-inorganic complex supplement: 7 parts of decomposed cake fertilizer + 5 parts of ferrous sulfate + 200 parts of water mixed solution, apply to the roots every 15 days. Combined with foliar application of 0.1% chelated iron solution for better results.
II. Pest Infestation Causes Yellowing Leaves
Control of Subterranean Pests
Grub larvae (beetle larvae) and ground beetles (H) feed on the roots at night, causing water absorption obstruction and yellowing leaves. Use 5% phoxim granules at 30g/㎡ mixed with soil or apply tea seed cake extract to the roots for biological control.
Control of Sucking Pests
Spider mites, aphids, etc., cause spotted yellowing. Alternate between using 22% spirotetramat suspension at 3000 times liquid and 1.8% abamectin emulsion at 2000 times liquid, focusing on喷洒ing the underside of the leaves.
III. Remedies for Cultivation Management Mistakes
Water Temperature Control Tips
In summer, well water should be sun-dried for 2 hours to bring the water temperature close to the soil temperature. In winter, it is recommended to use warm water at 20-25°C to avoid root cold shock leading to leaf yellowing and falling off.
Soil Improvement Measures
Add 30% decomposed leaf soil + 5% perlite to compacted soil, and combine with the application of EM bacteria-fermented organic fertilizer every spring to maintain the soil pH value within the appropriate range of 6.0-6.5.
IV. Strategies for Coping with Environmental Stress
Exposure to strong sunlight can cause sunburn-type yellowing leaves, requiring the construction of shade nets to maintain a 30%-50% shading rate. During the rainy season, pay attention to trench drainage as standing water for over 24 hours can lead to root suffocation and yellowing leaves.
By scientifically diagnosing the causes of yellowing leaves and taking targeted measures such as supplementing nutrition, preventing pests, adjusting the environment, and improving the soil, combined with regular pruning of yellow leaves to promote the germination of new buds, roses can be restored to a healthy state within 30 days. It is recommended to clean the leaves monthly and supplement trace elements to prevent the recurrence of yellow leaves fundamentally.