SHEATHS: Yellowing on Dozens of Apparently Healthy Plants

Ailments Orchid Doctor

by Robert M. [Bert] Hamilton (Compiler)

Originally published in The Orchid Doctor in 1980 and 1988

Posted by Sys Admin almost 8 years ago.

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The primary cause is not known; it is relatively normal on Cattleya mossiae and some hybrids; some may brown, soften and kill the buds; remove such. A74-34
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Sheaths Comments
SHEATHS: Blind On cattleyas are caused by insufficient light; hang them up close to the roof of the greenhouse. ODA72-134 0
SHEATHS: Browning C. skinneri sheaths naturally turn brown; but as it occurs more often in winter, poor light and ventilation either too dry or too humid could cause it; also too much water during the rest period; or the plant is just too plain weak to flower. OD88-9 0
SHEATHS: Bud On cattleya browning and dying off of sheaths is not likely to be caused by ethylene which would require a high concentration to cause it; most common cause in not known; to save the flowers remove the sheaths when they are yellowing. A77-922Yellowing or rotting of sheaths is caused by some factor unknown; if sheaths dry after yellowing, the buds inside should develop normally; remove early. A67-572; A80-513 0
SHEATHS: Buds Appear with No Sheath On cattleyas this is not unusual; not a disease, but characteristic. A70-631 0
SHEATHS: Buds Die Inside The cause may be dry rot or soft rot; after the yellowing, dryness will not affect normal development of buds; rotting and browning should be avoided by removal of the sheath; directions and illus. of removal. AH58 0
SHEATHS: Cattleyas Buds rotting inside can be caused by an accumulation of moisture in the sheath; caused by excessive watering, high humidity or rapid temperature change; do not overwater; cut off the tip. F77-16Do not mature in Louisiana; flower bud formation is influenced by length of day plus night temperature which can be too high in Louisiana; perhaps lighting left on in the growing area. A76-1007Drying of sheaths is common on winter and spring bloomers; remove them when they begin to yellow by tearing strips of the sheath downwards carefully to the pseudobulb, to let the buds develop; moisture and condensation in the dying sheath causes bud loss. A85-435No sheaths at all are produced; the cause in not known. A76-115; stimulate with good light and fertilizing. A80-630They appear but produce no blooms; the cause may be excessive fertilizing; remove the sheaths. A69-424; A75-1090They turn black and withered mostly because of water standing in the leaf-blade where the sheath begins. A83-24They turn... 0
SHEATHS: Double It is not uncommon for one sheath to form inside another on cattleyas; flowers develop properly; remove any yellow outer sheaths. A72-151; A76-1007; OD73-2On cattleyas; C.labiata or its hybrids normally have a double sheath; it should flower in the fall. OD73-2 0
SHEATHS: Dry It is a normal condition with Cattleya mossiae, and its hybrids and some other cattleyas. OD73-2 0
SHEATHS: Growth Is Poor and After Starting They Turn Dry or Brown The cause is not fully known; may be caused by air pollution or poor health, or not enough light; remove the sheaths, the buds will usually bloom. A76-795 0
SHEATHS: Infection, Bacterial It occurs particularly in hot, humid climates; caused by Pseudomonas bacteria; Physan 20 provides partial control; use it at 1 cc. per gal. of water as spray. A74-780+ 0
SHEATHS: Removal Effect on Buds Removal of the sheath does no harm but the bud stems may be weakened. A72-55 0
SHEATHS: Rotting Caused by Water Apparently water collecting around the base of the sheath can rot both sheath and buds within; illus. A77-436 0
SHEATHS: Sequence of Growth The sheath develops along with the new pseudobulb growth. A63-478 0
SHEATHS: Within Sheaths In cat tleyas a sheath growth inside another sheath is a heritage from Cattleya labiata which does it most frequently; why? A87-616 0
SHEATHS: Yellowing Causes are not fully known, although ethylene can be suspected; some plants produce sheaths which yellow than go brown before the buds are initiated and they still flower normally. A82-122 0

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