Orchid Culture Questions and Answers
image

 
Orchid Culture - Questions & Answers from This Month
by Sue Bottom, from the St. Augustine Orchid Society Newsletter
Email us with any orchid question, if we can't answer it we'll find someone who can! Send photographs too!
Click image for close up view

Dripping Sticky Stuff from Phal
 

Dripping Sticky Stuff from Phal

Q. I have 6 orchids that all seem to have a sticky deposit on the leaves. The sticky stuff drips onto the table they stand on and the windows they are next to. I did try gently just wiping the leaves with damp tissues, but it all reappeared. There are no evident creatures but I note that there are now brown patches on the underside of some of the leaves.

A. Those little brown spots are scale, they are in fact sucking insects pulling the plant sap out of the leaves. Get a bottle of isopropyl alcohol, pour a little into a cup, get some Q-tips and get to work, rubbing the scale off each leaf, upper side and underside of each leaf. Then pour some alcohol into a spray bottle and spray the alcohol into the crevices between each leaf to kill anything that is lurking there unseen. You may have to repeat the spraying weekly for a couple of weeks, then just watch for reemergence of the scale.   (Apr-17)


Cattleya Sheath Doesn't Develop
 

Cattleya Sheath Doesn't Develop

Q. I inherited several cattleyas that a friend purchased at an orchid show. Iíve had them a couple of years now, and had two instances of overwatering from which they have somewhat recovered. Several times the leaves have produced what I think is the flower sheath, but it never flowers, just eventually sort of yellows and withers away. Any advice?

A. Sometimes immature plants or plants growing in low light don't have enough energy to produce flowers so they produce a blind sheath, one that never blooms. If your friend purchased the plant at an orchid show, I would presume it was purchased in flower which suggests it is a mature plant. Next question is it getting enough light to generate enough energy reserves to be able to flower. If you are growing indoors, it is often not bright enough for cattleyas. Do you have a sunnier location it can be moved to (not quickly for fear of sunburn!) or is there a place you can put it outdoors when it warms up where it is protected from the midday sun but bright the rest of the day? In strong growing plants, there are some that bloom from the green sheath when that growth matures and some that rest after the growth matures and after several months of resting the bud forms into a flower. Don't give up, you just may have to experiment a bit to get the cattleyas into bloom, but they're worth it!   (Apr-17)


Leaf Mottling
 

Leaf Mottling

Q. I have leaf mottling on some plants. I have been told that the problem was either caused by cold spells for which I was not prepared, or a nutritional deficiency. What do you think?

A. I used to get that leaf mottling on my cattleyas, patches of lighter and darker green. I think the root cause is magnesium deficiency that shows up when plants are stressed from exposure to too hot or too cold temperatures that damage the chlorophyll. Magnesium is a major component of chlorophyll and the leaves that develop with insufficient magnesium are more susceptible to damage. Our water in Florida is very magnesium deficient, mine for example has about 150 ppm Calcium and only 7 ppm magnesium, far from the recommended 2:1 to 4:1 ratio. of Ca to Mg you're supposed to have. You probably need at least 20 ppm magnesium and Tom Sheehan's study indicates 50 ppm Mg is optimum for cattleyas. I use Epsom salts with every watering/fertilizing and strive for around 30 ppm Mg. Get your water tested so you know what you're dealing with and then you can figure out what magnesium supplement would be compatible with your fertilizer. You may not reverse the prior chlorophyll damage, but you can prevent it from showing up on new leaves.   (Apr-17)




 
image