Leaf problems - Deformed or have a residue on them

Symptom Link Description
Leaves have ridges Genetics
This usually indicates a ploidy issue. Most orchids are normally diploids (2 sets of chromosomes), but with breeding and genetic manipulation this can be increased to triploids (3 sets) or tetraploids (4 sets) or even higher. Plants with higher ploidy are produced by breeders because they often have improved flowers that are more richly colored or bigger. Along with this though, some anomalies often occur. The most common of these are increased tissue in the flower, or longitudinal ridges in the leaves. This is not a problem, other than looking a bit odd. The plant should grow and bloom without any issue.
Leaves are pleated or folded Culture problem
Newer leaves develop a pleating or folding as they emerge. The fundamental problem is that not enough water is getting to the leaves during their development. This can arise from several causes :
  1. plant needs more water, or more frequent watering
  2. temperatures are too high
  3. root loss has occurred
Since most people over-water their plants, number 1 in the list is unlikely. If the temperatures are too high, try providing more shade to keep the plant temperature down. If you suspect root loss, then please refer to this information.
Leaves on paph have stripes Variegation
Leaves have developed yellow or whitish stripes lengthwise in the leaf. This occurs occasionally in paphs and cannot be reversed with cultural changes. Most often it arises due to some genetic incompatibilities in hybrids between distant paph groups. Many of these will then produce deformed flowers, due to this incompatibility. It is best to avoid choosing such plants for your collection, as you will likely be disappointed in the blooms produced.
Leaves on non-paph have stripes Variegation
Leaves have whitish or yellowish patterns or striping in the leaves. This is perfectly normal, and often desireable, especially with certain varieties of chinese cymbidiums. You could even see this appear as a mutation in other genera in your collection, where one lead will develop variegation. If you want to preserve this, then wait until you have at least two or preferably three growths that show variegation before dividing the plant. This allows the mutation to stabilize, so that it won't revert to green leaves after separation from the main plant. Please note that yellowish variegation still contains chlorophyll, but white variegation does not. That is why white-variegated plants usually grow at a much slower rate than green-leaved plants.
Underside of leaves is sticky Click Here
Leaves have dewy droplets on the undersurface that makes them feel sticky to the touch. A few droplets along the leaf ribs or bloom spikes is normal, but an over-abundance likely indicates a pest problem. This problem is usually followed by the problem below, or a silvery sheen appearing on the leaves. Warm soapy water can be used to remove the residue, but the treating the pest problem will address this problem longer term.
Underside of leaves has a dark residue Click Here
Leaves have patches of dark, sooty residue on the undersurface that looks smudged or finely granular. This problem usually follows the problem above. The dewy droplets lead to sooty mold growing, giving these symptoms. This is also indicative of a pest problem. Warm soapy water can be used to remove the residue, but the treating the pest problem will address this problem longer term.
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