Causes and Solutions for Yellowing Orchid Leaves
Yellowing orchid leaves or scorched leaf tips are a common phenomenon, mostly a physiological disorder, which not only damages the integrity and ornamental value of the leaves, but also seriously affects the healthy growth of the orchid plant, and can even cause the premature death of the whole plant. The situations in which orchid leaves turn yellow and leaf tips scorch are complex, and the overall cause is improper cultivation and care. Let's take a look below at what to do when orchid leaves turn yellow!
Yellowing leaves caused by excessive light
Orchids are semi-shade plants, suited to morning light, diffused light, and soft light. If the light duration is too long and the light intensity too strong, it very easily causes the leaves to turn yellow and the leaf tips to scorch. The countermeasure is to adjust the light duration and light intensity in a timely manner during summer and autumn to avoid direct strong light. The most commonly used and simplest method is to use shade nets of different specifications; the shading level is generally 60%-80% for ordinary varieties, and must reach 90% for variegated-edge, striped, crystal, and patterned varieties.
Yellowing leaves caused by dry air
When the air is moist, orchid leaves are emerald green and glossy, radiant and striking. If the air is dry, the leaves are coarse in texture, and tip scorching occurs from time to time. Especially in the dry, rain-scarce, windy north, where the air is often dry in spring, autumn, and winter, orchid leaf tip scorching is particularly severe. The solution is, when the air is dry, to frequently mist the leaf surfaces and sprinkle water on the ground. You can also place a water trough under the orchid pots, build a water pool in the orchid shed or orchid room with nylon cloth, hang wet door curtains, and install automatic misting humidifiers.
Yellowing leaves caused by improper watering
Like other plants, orchids cannot do without water, and insufficient or excessive watering will cause losses. There is often this situation: because the potting soil is too full, water flows out as soon as it is poured, resulting in the top being wet and the bottom being dry, forming “half-way” watering. Over time, because the root system loses water, scorching first begins at the leaf tips. Another reason is that due to carelessness, watering is missed, and this phenomenon is also prone to occur. On the contrary, whether it is soil-based or granular planting medium, if watered on schedule and in equal amounts, the soil-based medium becomes too wet and lacks oxygen, breathing is not smooth, the root system turns black and even rots, causing orchid leaves to dry up and tips to scorch. The countermeasure is to water timely and appropriately according to the growth habits of different orchids, preventing the occurrence of the above two undesirable tendencies.
Yellowing leaves caused by excessive fertilisation
Orchids have fleshy roots and live symbiotically with orchid mycorrhizae, so only light fertiliser applied frequently is needed for them to grow robustly with lush leaves and fragrant flowers. If fertiliser is applied excessively, especially if raw or concentrated fertiliser is applied, it will cause root rot, yellowing leaf tips, and premature ageing. The correct approach is to fertilise timely and appropriately according to different orchid varieties, different growth stages, and different growth conditions. For root fertilisation, liquid fertiliser made by fermenting organic fertiliser must be diluted with 1:10-20 times clean water before use, while chemical fertiliser should be prepared at 0.1%-0.2% and applied about once a month. Foliar spraying of fertiliser should be dilute rather than concentrated. If using micro-fertilisers such as orchid mycorrhiza king or spraying treasure, be sure to prepare them according to the product instructions, and do not arbitrarily increase the concentration, to avoid causing fertiliser damage.
Yellowing leaves caused by abnormal leaf physiological function
Some cases are due to excessive nitrogen application, which makes the leaves tender and reduces stress resistance; some are due to spraying fertiliser or pesticide at too high a concentration, which accumulates at the leaf tips and causes damage; some are due to inadequate cold protection measures in winter, causing frost damage to the leaf tips. There are also cases where the orchid pots are spaced too closely, and leaf tips rub and collide with each other, causing damage. The measures to take are to treat according to the specific cause and address each case accordingly. That is, apply the three elements nitrogen, phosphorus, and potassium rationally; when spraying fertiliser or pesticide, it is better to use a dilute rather than concentrated solution; do a solid job of cold protection and warmth keeping in severe winter and early spring; and increase the distance between pots to prevent the occurrence of phenomena affecting leaf physiological function.