Why Are Orchid Leaves Turning Yellow? An Analysis of 12 Types of Yellowing Leaves

For novice orchid growers, encountering yellowing orchid leaves is not uncommon, but many hobbyists cannot figure out the cause of the yellowing. This article is a summary by an orchid grower of 12 types of yellowing leaves in orchids, and it is hoped it will be helpful to fellow orchid growers.

1. Old-age yellowing

Age takes its toll, and the form wastes away. With vitality failing, the leaves naturally and quietly turn yellow. This generally occurs on back-bulb shoots several generations old; whether the yellowing goes from bottom to top or top to bottom, there is no great harm.

2. Brooding yellowing

This is a reaction during the gestation of a new shoot and often keeps pace with the new shoot. Sometimes the yellowing is slow, sometimes fast; sometimes it starts from the edge leaves, sometimes yellow and green alternate. The outcome is——the new shoot grows quickly but new roots have not yet emerged, and as a result both mother and child die together. This is why weak seedlings with shoots introduced in summer are prone to problems.

Or the new shoot gradually grows, new roots gradually emerge, and once it has the ability to stand on its own, the two support each other and get through the difficult period.

3. Water yellowing

After prolonged rain, the new shoot suddenly bolts, with the lower part white and tender, while the leaf sheaths turn yellow; this is exactly what happens. It generally does not turn black but slowly withers away, and reducing watering will take care of it.

4. Fertilizer yellowing

Generally, in heavily fertilized plants, the leaf sheaths turn yellow first and then black. In cases of severe fertilizer accumulation, there will be moldy black patches in the leaf grooves of old leaves. Or, even if the fertilizer is not heavy, prolonged accumulation can cause the same.

5. Soft rot yellowing

Soft rot is bacterial, watery and soggy; the yellowing is not very obvious because it moves too fast, and the leaf bases become soft and rotten. The difference is that the leaves show signs of dehydration and loss of color.

6. Stem rot yellowing

There is a dry-type yellow at the leaf bases. Or a pale yellow, either of which should draw attention. Stem rot starts from the stem, then spreads to the pseudobulbs at each node, and afterward shows on the leaves, with little dehydration sign, breaking at a touch. So the tiring part of growing orchids is having to inspect them constantly.

7. Yin-yang imbalance yellowing

First the plant is exposed to the sun during the great heat period, then suddenly you feel sorry for it and quickly move it into a room, and some even turn on the air conditioner. The orchid's reaction is yellowing of both new and old leaves, and in severe cases they scatter and fall profusely. It occurs most often in Cymbidium ensifolium. So it is best to move it to a shaded spot outdoors and let it transition slowly. When yin and yang are out of balance, the stomata open and close wildly, causing physiological disorder.

8. Water damage yellowing

When rain enters during the shoot-emergence stage, or when misting the orchid leaves to cool them and raise humidity, in fact fine mist more easily enters the leaf core, and water accumulates in the leaf core, blocked by the leaf grooves and unable to dry out; in severe cases it induces pathological soft rot, and in mild cases it causes physiological water damage. After the leaves unfold, scars appear, characterized by water-damage spots that are often left-right symmetrical

This kind of water damage, I estimate, is related to uneven hot and cold; when they are not in harmony, the qi is forced.

Otherwise, if you fully submerge an orchid in water for a night, the new shoot would not necessarily develop water-damage spots, would it?

9. Root rot yellowing

The cause is unknown; the characteristic is that the whole clump quickly withers and yellows, dehydrates and dries up, while everything below the leaves of the whole plant remains intact.

10. Sunscald yellowing

Yellow-white, either in patches or across the whole leaf, sometimes showing at the leaf tip, hard and yellow throughout. When orchid resources were scarce, people thought it quite rare, and then looked in books and said it was a sign of "chushuixian," and were delighted; in fact it is merely sunscald yellowing of Yangshan grass, and it disappears after shaded cultivation.

11. Slight stuffy yellowing

It occurs most often on the central leaf. Just one leaf. The others are intact. It occurs in both spring orchids and Huilan; you may pull it out, you may cut it, or you may neither pull nor cut it. It is related to the potting medium, to water and fertilizer, to the placement environment, and to temperature and humidity

The pseudobulb of an orchid is jointed; the leaves and flowers grow on the rings of nodes, and the central leaf is actually like the terminal node of a daylily, and it is fine to break it off. Although it does not harm the base, it should still raise vigilance.

12. Variegation yellowing

If it produces a central translucent pattern, produces colorful flowers, produces tender yellow crystal, produces tiger stripes——then congratulations.