Orchid Culture Questions and Answers
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Questions and Answers from 2017
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!
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Orchids Left Out in the Cold
Orchids Left Out in the Cold
 

Orchids Left Out in the Cold

Q. I left these outside during the cold wet weather. Yikes! They're inside now, what do I do?  

A. The phalaenopsis may be a goner. Whether the damage is from the freezing temperatures or dripping cold water, the cells have collapsed and been invaded by bacteria. You can remove the leaves, spray the entire plant with hydrogen peroxide or one of the copper fungicides/bactericides. Put it in a warm place and then you wait, perhaps a basal keiki will form.
    The other orchid, a Grammatophyllum perhaps, also has some extreme cold damage. Remove those leaves that are totally or mostly brown. If you choose to keep some of the greenish leaves, spray them with peroxide and watch the leaves. If the discolored areas continue to enlarge, remove them. There is a lot of energy stored in those pseudobulbs, so your hope is that they will sprout new healthy growths in the spring.  (Feb-18)


Dendrobium Leaves Yellowed
Dendrobium Leaves Yellowed
 

Dendrobium Leaves Yellowed

Q. I have has this phal type dendrobium for several years. The plant is in a southeast window with some phals (house temp about 65 F, about 60 miles north of NYC). It hasn't produced many spikes over the years but it has 6 canes that had, until a couple of days ago, green leaves and was looking pretty happy. Is the leaf yellowing a bad thing?   

A. The phalaenthe dendrobiums are very cold sensitive. I am guessing it was too close to the window on a cold night. The good news is that dendrobiums are tough. As long as the canes are hard, they'll probably come back. Feel the canes from the base to the top looking for any soft or dessicated spots. It looks like the canes are a little deep in the pot, why don't you try picking some of the bark out of the top of the pot until you can see the rhizome, then feel the cane at the very base to make sure there is no rot. If nice and hard, find the brightest spot you can in the house and just wait and watch, cut back on watering to say half your normal rate until you see some new growth.   (Feb-18)


Psychopsis Leaf Yellowing from Base
 

Psychopsis Leaf Yellowing from Base

Q. Just noticed the base of leaves of this Psychopsis are turning yellow. Do you think the two nights below 60 caused this?

A. I don't think it's the cold weather; those Psychopsis oncidiums can be very temperamental. I think it is a form of rot that comes up from the roots through the pseudobulb to the leaves, possibly rhizoctonia cause it isn't fast like black rot. When that yellowing occurs, that part of the plant is probably toast. Move the organic matter away from the pseudobulbs and from above the rhizome. See if there are any roots attached to the oldest pseudobulbs and whether the bulbs are hard or soft. If the roots are gone, the bulbs softening, cut them away and then decide whether you should repot, which could hasten the end, or let the plant try to recover, in which case give it a Banrot drench.
  I've lost beautiful psychopsis that went from having 6 consecutive flower spikes blooming like mad to exhibiting this slow moving rot where one leaf after another drops. I've had some suggest it's salt accumulation, though I've rarely found a high salt content in the coarse mix. I keep mine in a somewhat shadier spot than the cattleyas in a mostly inorganic mix. Just leave them alone, let them grow out of the pot and don't disturb the roots, sometimes a leaf yellows and drops and as long as the bulb is hard, just let it do its thing.   (Feb-18)


Enlarging Rings on Orchid Leaves


 

Enlarging Rings on Orchid Leaves

Q. I have these rings on a Gongora, as well as two other orchids. It starts with one leaf, I cut it off and later on, other leaves develop the same problem. I thought it might be the sun at first but I remember reading that circular patterns are a sign of virus. Should I trash these 3 orchids fast?

A. I don't think that's a virus, it looks like classic Anthracnose, that is caused by one of the leaf spotting fungi. You should be able to see tiny little dots in the discolored area, those are the spores that spread the disease. You can remove the diseased leaves to a closed container. Fungicides can be sprayed to help prevent spores from settling on leaves and spreading the infection. More air movement and less leaf wetness will help prevent the conditions that favor the disease.   (Jan-18)


White Crystalline Material on Potting Media
 

White Crystalline Material on Potting Media

Q. What is this white stuff all over my lava rock? I am repotting cause so many roots were growing out of the pot on my oncidium.

A. Quite a mystery! It's not snow mold. That grows on organic media, and this substance is crystalline. You might think salts precipitated out of the water, but then why are the roots so healthy,with none of them burned? Courtney says there are some bacteria that make colonies and use dissolved minerals as an energy source. The white material, possibly calcium carbonate, dissolved when dropped overnight in a solution similar to vinegar. It doesn't seem to impact the health of the plant. Just another of life's little mysteries!   (Jan-18)


Oozing Spot on Phalaenopsis
Oozing Spot on Phalaenopsis
Oozing Spot on Phalaenopsis
 

Oozing Spot on Phalaenopsis

Q. Someone just gave me this orchid and I canít identify its problem. Can you help identify it and give me some treatment options?

A. The bottom leaf has soft rot, that leaf should be removed immediately. If the rot travels to the crown it will kill the plant. The upper and lower surfaces of the other leaf looks comprised as well. If the plant has enough other leaves to sustain it, you might consider removing that leaf too. Then get a fresh bottle of hydrogen peroxide, or better yet one of those spray bottles of peroxide that Walgreen's sells, and spray all the above ground portions of the plant, particularly around the crown where the rotting leaf was. If you were just given the orchid, then you don't really know what happened to it before that allowed the rot to get to the plant. You'll just have to keep an eye on it to see if you stopped the rot in time. If you're a cinnamon person, you could dust the crown of the plant and around the cut edges after the peroxide dries. The cinnamon will dessicate that portion of the plant and create a barrier so bacteria can't invade.   (Jan-18)


Phal Leaf Didn't Open
Phal Leaf Didn't Open
 

Phal Leaf Didn't Open

Q. I rescued this tiny Phalaenopsis about four months ago. It was dehydrated due to total root loss other than 4 small aerial roots. It has shown some improvement, the leaves are no longer limp, and it has managed to grow two more aerial roots. I am not sure if there any new roots growing in the media yet. It also started to grow a new leaf about 2 months ago but it has shown no signs of opening up by now. Why?  

A. Your plant is going to be fine. I like your mix, the addition of sphagnum moss to the bark, that will help hold a little moisture cause bark oftentimes is hard to get hydrated when you first put it in the pot. The mix looks perhaps a bit dry, are you growing indoors where the humidity is low? Are you watering once or twice a week? One thing you can do is put a thin layer of sphagnum on top of the pot to help hold a little moisture at the upper end of the pot where the tender new roots will form. If you just repotted and the leaves are starting to lose their leathery look, I'd say your plant is well on its way to recovery. Make sure it's getting enough water and it'll come out of its holding pattern and the leaves will start enlarging. A few weeks later Alicia wrote back, "Good news! The leaf is now open!"   (Jan-18)


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