Orchid doctor

LEAVES: Yellowing of Premature Growth

Ailments Orchid Doctor

by Robert M. Hamilton (Compiler)

Originally published in The Orchid Doctor in 1980 and 1988

Posted by Sys Admin almost 2 years ago.

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Can be caused by improper feeding, or drying, or low temperature, or poor aeration in the pot. A79-910
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Leaves Comments
LEAVES: Bifoliate Have a tendency to weak growth if grown in too much shade; color should be olive green, not dark green. OD66-124Suddenly appear on a labiate plant; good culture causes it. A69-242 0
LEAVES: Black Tip Control: it is probably a fungus; if the area increases in size, spray with Banrot at 1 ttpg. A79-370 0
LEAVES: Black Tips They progress downwards rapidly to the pseudobulb; probably black rot; spray with Truban (Terrazole); provide good air circulation. A78-112 0
LEAVES: Cleaning Salts Off Use 1 teaspoon vinegar in a cup of water, also use cotton swabs and water to wash the surface clean of salts or other coatings. OIE88Jan-7; citric acid 1 tbsp. to 1 qt. warm water. OIE88Mar-2 0
LEAVES: Cleaning Them For show display it is legal to clean them with 1 pt. evaporated milk to 10 pts. water; it's illegal, however, to use a "leaf shine" preparation on plants to be judged; they also harm the leaves. OIE88Feb-8 0
LEAVES: Clear Liquid Drops At Tips Caused by a sap exudate stimulated by moist media and humidity; it is normal. A77-108 0
LEAVES: Damage Leaf damage can be caused., by two things,a. disease or fungus or, b. insect infestation; remains of insects are never found because they leave after doing the damage; Yellow streaks followed by silvery pitting then browning and loss of tissue is almost certainly caused by phalaenopsis mites which also attacks cattleyas, dendrobiums, oncidiums and of course, phalaenopsis; for them apply miticide four times over forty days. OR80-209 0
LEAVES: Emerging From Center of New Growth As in cymbidiums, vigorous new growth in the center is desirable to promote as large a bulb as possible on maturity. OD68-172 0
LEAVES: Fungus Treatment Spotted and pitted leaves require treatment with a paste made of captan or other fungicide; coat the whole infected area and let the paste dry; wash the bench with captan in water and spray all the other plants around; continue to maintain moderate humidity for some time and keep the fans blowing. OR83-11 0
LEAVES: Hard Water Deposits It is difficult to remove them, the best bet is to scrub the deposits with lemon juice or a very mild acid solution, and rinse it off after. A82-1259 0
LEAVES: Mesophyll Cell Collapse This happens especially in phalaenopsis and is caused by cold water dripping off the roof or from the hose onto the leaves; the scars become visible about six weeks after. F81-14 0
LEAVES: New Ones Do Not Open They remain partly closed; try periodic syringing in the morning; there is no definite remedy. A78-226 0
LEAVES: Old and Browning Caused by old age or root injury. A78-226 0
LEAVES: On Ascocendas Have Bacterial Leaf Rot Bordeaux mixture is not very effective against bacteria, so use Physan at 15 ml. per gal. of water. A74-792 0
LEAVES: On Cattleyas Are Black Edged Inadequate light contributes to dark, soft growths which are not self-supporting; brown, drying edges indicate root injury. A71-1021 0
LEAVES: On Cattleyas Are Drooping Check roots for possible bush snails or for over-watering; the root system is the key to healthy plants. A77-449 0
LEAVES: On Cattleyas Became Sunburned Do not put in shade but in good light out of the sun and heat and avoid over-watering. A72-204 0
LEAVES: On Cattleyas Become Yellowed If some have black splotches it may be caused by excessive soluble salts, or by toxic salts. A78-495 0
LEAVES: On Cattleyas Go Limp Too much nitrogen fertilizer, with too low light supply can cause it; poor root condition, such as too wet may be the fault. A72-686 0
LEAVES: On Cattleyas Go Limp and Wrinkled Possible injury to roots is the most likely cause; caused either by over-watering or excessive drying. A76-115 0
LEAVES: On Cattleyas Have Black Tips On new growth it goes no farther than the pseudobulbs; spray with Truban or Terrazole, at 1 tpg. A79-4 0
LEAVES: On Cattleyas, Have Purplish Spots Many pigments are masked until a cultural change takes place; higher light levels turn leaves purple; also, a nutrient deficiency can cause the color to appear; the areas around insect punctures turn purple; Florida red scale can infest a plant even in Ohio. A83-6000 0
LEAVES: On Cattleyas Show Shrivelling Suspect dryness of culture; cattleyas like high humidity, but too heavy watering can kill the roots. A75-1007 0
LEAVES: On Cattleyas Stay Folded Possibly caused by too low atmospheric humidity. A76-14 0
LEAVES: On Cattleyas Stay Long and Narrow If they fail to spread open it is possibly because they lack sufficient light. A77-995 0
LEAVES: On Oncidiums Are Accordion-folded In a window area this could be caused by too low humidity; the effect of misting lasts only 1/2 an hour. A75-1096 0
LEAVES: On Paphiopedilums Bend in the Middle and Slump Over Turgidity is lost when medium is too dry or the humidity is too low; dark weather may cause it. A75-298; OD73-158 0
LEAVES: On Phalaenopsis Droop Suddenly Cool nights followed by sunny mornings can trigger this, or excessive drying. A75-437 0
LEAVES: On Phalaenopsis Have Thin Marginal Edge with No Chlorophyll and Some Turn Blackish Cause not known; may be due to excess salts in the water, or accumulated in the medium. A75-298 0
LEAVES: On Phalaenopsis, Show White Patches Damage by cold water causes sunken cell wall collapse; water dripping from the roof in winter causes it. F85-8 0
LEAVES: On Vandas Turn Yellow and Drop Repot the plant in loose medium dampen it and place in a plastic bag in indirect light. A75-35 0
LEAVES: Purplish Pigmentation Caused by too low night temperatures, or too bright daylight; also caused by lack of adequate phosphorous. A64-693 0
LEAVES: Removal From Ailing Plant Most important is the removal of most leaves from a dessicated plant recently received with no roots; when little or no means to replenish water exists the plant should be relieved of a good portion of its parts which transpire, leaving only a minimum to carry on photosynthesis. ODA69-53 0
LEAVES: Removal Time Do not cut them off until they dry and shrivel and are ready to fall. A76-115 0
LEAVES: Samples Sent by Mail for Inspection Do not wrap them in Saran or polyethylene but in a single fold of waxed paper. A71-439 0
LEAVES: Shrivelling on Cattleyas Is caused by several things, such as dryness of culture, lack of high enough humidity, roots possibly dead from over-watering. A86-383 0
LEAVES: Sunburned The best treatment is to remove only the badly burned ones; partly burned ones are unsightly but still functional. A69-130; A75-906; A79-334 0
LEAVES: Sunburn Treatment Saturate a large amount of water in a pail with sugar and cover the plant in it to seal the tissues from fungi and bacteria and stop dehydration; after an hour or two remove and keep the burned areas covered; let the roots function as normally as possible. RMH; AU87-(l)-23 0
LEAVES: Testing for Virus The expert relies solely on visible symptoms on leaves where they are apparent; the lower portion of a maturing leaf in doubtful cases can be sent for instance to Florida West Coast Scientific Labs. P.O.Box 11914, Xampa FL. 33610; the charge was reported low in 1973. A73-503 0
LEAVES: Transpiration The technical principles involved for the grower; refer to AU85(1)-31 0
LEAVES: Variegated Green and White The plant was negative when tested for virus; it is possibly a variegated sport. A61-658; illus. of an awarded plant. A77-831 0
LEAVES: White Patches Check the Mg and Fe levels in the fertilizer and increase one or both. Au84-204 0
LEAVES: White Patches on Phalaenopsis Most likely this is caused by cold damage which results in sunken cell-wall collapse, likely on plants too near a cold wall or under a cold-water drip; always use water for watering which is warmer than the temperature of the house. F85-8 0
LEAVES: Whitish Build-up From Minerals in the Water Additive available to dissolve it: use mild detergent to help remove the deposit; an ion-exchange demineralizer is expensive; do not use water softener. A77-314 0
LEAVES: Wilting Without Changing Color, Leading to Death of Plant Too little light can cause it, or excessive wetness; check the roots for root aphids or fungus. A71-345 0
LEAVES: Wrinkled, Especially the Front Ones This indicates something seriously wrong with the plant; the beginning grower should check the roots and all cultural procedures. A72-117 0
LEAVES: Wrinkled Front Ones This suggests a cultural failure, so check the roots first and then the other cultural practices. A85-1118 0
LEAVES: Wrinkling on Cattleyas This is caused either by overwatering or under-watering, so take your pick; disease is not likely to cause it; also, check the roots. A81-969 0
LEAVES: Yellowing Usually caused by too high light levels and indicates the lighting should be reduced by 25 to 50%; also, increase the Mg and Fe in the fertilizer. Au84-204Young leaves on new cymbidium shoots turned yellow but a dose of iron cured the plants. Au81-102 0
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