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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Spots on Catasetinae Leaves
 

Spots on Catasetinae Leaves

Q. What are these spots on my Monn. Millennium Magic 'Witchcraft'?

A. Those are the wounds left on your tender young catasetinae leaves from thrips, who fly around seeking out the tenderest juiciest orchid tissue they can find. They feast on green root tips, young leaves and flower buds ruining them before they have a chance to mature. They are very difficult to treat because they are mobile, moving from plant to plant, and hard to see, although their damage is very obvious once you recognize it. The bulls eye in the center of the leaf spot is the give away that it's thrips. One relatively affordable pesticide with systemic action against thrips is Avid. If thrips are prevalent in your area, you might consider a weekly preventative spraying program. Check out the website for tips on how to declare war on these marauders.   (Aug-17)


Sudden Leaf Damage
 

Sudden Leaf Damage

Q. I brought a couple of new cattleyas home, and when I looked at them the next day they didn't look good, brown or black rot?

A. The leaf is sunburned and the damage is pretty extensive. It also looks wet so secondary infections are possible. You may want to remove that damaged leaf to prevent disease from entering the healthy part of the plant.   (Aug-17)


Should This Phal Be Repotted
 

Should This Phal Be Repotted?

Q. This is a nice healthy plant. Should I just set it in a clay pot and hang it at a 45 degree angle?

A. You can drop it into a clay pot as long as the moss is still in good shape. If the moss is starting to degrade, you will have to repot and that will be a bit tricky because you've got roots growing beneath the leaves and deep in the pot, but the stem is rootless along much of its length. Maybe a better choice would be to just water blast and pick away the moss until you have removed most of it, cut away any of the woody stem below fat healthy roots, drop it into a new pot and backfill around the roots.   (Aug-17)


Purely Organic Fertilizer Issue
 

Purely Organic Fertilizer Issue

Q. I put 1 tablespoon of Purely Organic in a tea bag. The bag sits on the mix and I water through the bag. After 2-3 weeks, there is a blue green powder, mostly on the underside of the bag (the side in contact with the mix). Any thoughts on what it is and if I need to do something about it?

A. It is probably some sort of bacterial or fungal growth, should not be a problem. I think one of the ways Purely Organic works is to stimulate the microflora around the roots.   (Aug-17)


Spotting on Cattleya Leaf Tips
Spotting on Cattleya Leaf Tips
 

Spotting on Cattleya Leaf Tips

Q. My Epc. Plicaboa has an ongoing problem with spotting on the backside of each leaf tip. I have treated it with Dithane and Thiomyl regularly, but the problem persists. It usually stays on the backside, however some of it shows on the front side of the leaf. The plant is fine otherwise, and blooms regularly, but the leaves are rather unsightly. I was told this may occur as a result of heat stress?

A. If I had to guess, I'd say bacterial brown spot. Spray with one of the copper compounds, they are great bactericides. Dithane and thiomyl are good fungicides, but won't work on a bacterial infection. You may have to remove the severely damaged leaf tips, but it is usually a pretty slow moving disease in adult cattleyas.   (Jul-17)


Fuzzy Growth on Phals
 

Fuzzy Growth on Phals

Q. What should my neighbor do with this orchid?

A. That looks like a mealybug infestation. If there are that many on the flower stem, they are likely also hiding in leaf crevices and on the roots. Get a spray bottle of isopropyl alcohol and spray the flowers, flower stems, leaves, etc. all the aerial parts of the plant. Check the plant every day for mealybugs because they are very difficult to get rid of. You can drench the pot with one of the pesticides containing imidacloprid. If they are on the roots, you may have to bare root the plant to find all the mealybugs and then repot.   (Jul-17)


Angraecum Leaves Yellowing
Angraecum Leaves Yellowing
 

Angraecum Leaves Yellowing

Q. This is Angraecum Lemforde White Beauty (sesquipidale x magdalene). Iíve had this plant for about 2 years, it has grown and bloomed a couple of times. It is prone to some leaf spotting fungus at the tip of the leaves because they are like saucers holding water. This year whatever is happening begins at the edge of the leaf closer to the base, it looks like brown edging. The roots look fine except they have no growing tips and the other angrecoids I have are busy growing roots now. I sprayed my whole collection a week ago with Banrot. About 3 months ago when this first started, I cut off the the edge of 2 leaves, sprayed with peroxide and that seemed to stop the process but itís back. Could it be fusarium wilt?

A. Looking at the plant, two possibilities come to mind. The most troublesome would be one of the bulb, stem or root rots like Fusarium or Rhizoctonia. I don't see the wilt, or the graying tissue like you might expect with Fusarium, and if it were Rhizoctonia, you would expect it to be moving up the stem affecting the lower leaves first, not the fourth and the eighth leaf up. So I'm guessing that is not the problem.
  The other possibility is that water has been pooling in the leaf axils causing the problem. It looks like there is some rot around the leaf bases and of course the leaves are so close together it would be easy for water to collect, and then opportunistic bacteria or fungi could start growing. If that is what is happening, pour some peroxide into the leaf axils and figure out a way to reduce leaf wetness.
  Lucy wrote back "I think you are right on the tightness of the leaves possibly contributing to the fungus at the axils. I realized recently that the angraecums that get direct eastern wind off the pond that the house back up to are happier campers. Wind so strong sometimes it knocks them over but the leaves dry quickly. Iím going to move the Lemforde and a couple of other cranky ones to a very similar windy position and see how that goes."   (Jul-17)


You Never Know About Terry Bottom
 

What Would Terry Do?

Courtney Writes: This is the first C. Terry Bottom that bloomed, and is the one you kept while my greenhouse was being rebuilt. For some reason, it is sprouting new growths from up on the pseudobulbs; five so far. I did put a poo ball of Purely Organic on it, but I did that on most of my catts including other seedlings of C. Terry Bottom. I checked the other catts that you kept for me and none of them are doing the same thing. Guess one never knows what a Terry Bottom is going to do!   (Jun-17)


Leaf Bumps
 

Leaf Bumps

Q. I have recently started growing Catasetums. There are "blisters" or bumps mainly the upper leaf surface and they feel a bit rough. The plant has been growing in a west bathroom window with frosted glass on a humidity tray. The plan is to move outdoors to join the rest of my collection but I'm concerned it might have something contagious.

A. Those small bumps are edema, little water blisters from when the plant takes up more moisture through the roots than it can shed via the leaves. It happens when watering late in the day when the nights turn cool or when watering on a gray or rainy day. I've never heard of a plant getting it from shower humidity, but I suppose it's possible. It won't do much damage to the plant, which looks great!   (Jun-17)


Laelia purpurata
 

Laelia purpurata

Q. I've had this orchid for a long time. Last year it had 21 flowers, this year it has 40. Do you know what it is? I think it's the fertilizer I've been buying from SAOS.

A. OMG, that is an incredible Laelia purpurata (now they call it a Cattleya purpurata). I think it's not the fertilizer, you found the perfect place for it and are growing it perfectly. I hope you'll be able to lug it to the show table this month!   (Jun-17)


Dendrobium Leaves Sickly
Dendrobium Leaves Sickly
 

Dendrobium Leaves Sickly

Q. This is my first crisis with my orchids. I bought this Dendrobium at Home Depot 3 months ago. The plant appeared healthy, potted in sphagnum moss and was in bloom. I watered/fertilized weakly, weekly with bloom fertilizer. I repotted it earlier this month into a coco/charcoal mix. It resides in a southeast window with good circulation. Today I noticed a dropped leaf, in very poor condition. More mature leaves are turning yellow and withering. It has been isolated from all my other plants. I would be most appreciative if you would suggest a treatment.

A. If that Dendrobium has been doing well in sphagnum moss for 3 months, the leaf drop probably has nothing to do with what happened to it prior to coming to you. This type of dendrobium is very cold sensitive and doesn't like temps below 60F, and we had a couple of cold nights this spring. I wonder if the leaves were too close to the glass and got too cold during the brief cold snap, and then the problems began. Did it happen after the cold snap?
  The damage is consistent with cold damage, which causes cell collapse and then secondary pathogens can enter the leaves. If that's what happened, then remove the severely damaged leaves, spray what's left with hydrogen peroxide and wait for the dendrobium to grow. They are very resilient. Your potting mix is fine, I would just morph over to smaller pots with some peanuts or drainage materials in the bottom of the pot.   (Jun-17)


Vanda Roots Dried and Cracked
Vanda Roots Dried and Cracked
 

Vanda Roots Cracked

Q. I have a few vandas that have cracked roots and some that are very plump but yellowing. I am concerned this may be fusarium. I have treated with Switch already. I am hesitant to cut the stalk to check for the ring because I did that once and found no ring but ended up killing the vanda. Can you take a look at these roots and tell me it is a disease or just normal root death?

A. I think your vandas look totally happy and fusarium is probably not an issue. If it were fusarium, it would be travelling up the stem and lower leaves would be infected and dropping, and that doesn't seem to be what's happening. More likely it is just the natural aging process. It is a sympodial orchid that is growing upward and adding several leaves each year, so the bottom stem slowly gets woody and the roots attached to the woody dying stem likewise perish, but their function is replaced by the roots that emerge higher up. I'm starting to see new rootlets on my vandas, it's that time of year. I cut away the nonviable roots as they are brought out in the spring, just to get the pleasure of seeing all the roots green up when watering and fertilizing.   (May-17)


Cattleya Sheath Doesn't Develop
 

Cattleya Sheath Doesn't Develop

Q. This cattleya has just finished blooming two beautiful fragrant blossoms. I just noted a dark discoloration at the base of one of the leaves. The rest of the leaves appear to be fine. It had a small amount of scale at the base which I treated and otherwise has been healthy.

A. That scale infestation might have been a little worse than you suspected, it looks like it destroyed the tissue at the base of the pseudobulb. Scale will move from plant to plant, it also comes into your growing area from your outdoor plants. You should probably consider the possibility that you have scale somewhere on your plants, most likely in the papery sheaths at the base of the plant or in leaf axils. Put on your bathing suit, get a spray nozzle set on flat, and go through your cattleyas. Blast away all the papery sheaths on older growths, if they don't want to come off the younger growths, don't force them, but blast the plants and see what you find. When you're done, if you found scale, you can spray them all with a suitable insecticide.   (May-17)


Fusarium in Phalaenopsis
Fusarium in Phalaenopsis
Fusarium in Phalaenopsis
 

Fusarium in Phalaenopsis

Q. I have had my own catastrophic event with my phalaenopsis this winter. I have hundreds of phals and thousands of phal seedlings growing in my basement that represent more than 20 years of hybridizing. During one cold night I left the window open and the plants directly in front of the window got chilled. About a one month latter the plants started getting yellow spots that progressed to sunken areas followed by leaf death.
  The small necrotic spot at the center line of the leaf is frequently the first symptom usually at the base of the leaf. Sometimes I detect a very pale purple discoloration in the leaf that turns into a sunken spot on the underside of the leaf.
  Thanks for your article on cold stress and secondary fusarium invaders. I clicked on the link you provided and looked at the control page for fungicides. The fungicide ďSwitchĒ you recommended did not get a positive rating in the chart. I am confused as to why you chose this. I have been trying Daconil and Physan 20 but I donít think they are preventing the spread. Can you suggest a drench for the whole pot?

A. The Switch recommendation came from Hark Orchideen, a most excellent site to assist in the diagnosis and response to disease organisms. It was this site that led me to the fusarium diagnosis after my heater failure. Their website says "In the case of Fusarium infestation at the base of the leaves, spraying with Cyprodinil + Fludioxonil (Switch) can be useful to stop it spreading in the stand and get the infestation under control." Their recommendation for the use of Switch is basically to stop the spread of fusarium on the aerial parts of the plants, not to treat the basal or rooted portion. For drenches, Daconil, Heritage and Empress are highly rated.
  I have about a dozen plants that looked like they survived the infection and the next winter began displaying the symptoms again, from which I can only conclude that fusarium is incredibly difficult to eradicate. You may also have to get out the razor blades and cut away the severely infected tissue and then keep spraying and drenching.   (May-17)


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 Buds 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)


B. Little Stars
 

B. Little Stars

Q. I was hoping you could identify this orchid for me.

A. That looks like a B. Little Stars, a primary hybrid between B. nodosa and B. subufolia. It is incredibly well grown and flowered. Congratulations on your beauty.   (Mar-17)


Sick Catasetum pileatum
 

Paphiopedilum Roots

Q. I bought this Paph. primulinum in October. It just fell and before I repotted it I took these photos. The orchid looks great but there are NO green roots and there is no new root growth either. What are your thoughts? It is planted in Orchiata and Styrofoam.

A. The roots look darn good to me! Paphs are semiterrestrial so they have hairy roots more like plants that grow in soil. They do have a greenish whitish hairy root tip when the roots are lengthening. If they feel plump and hairy, they're healthy. Courtney swears by adding a teaspoon or two of dolomite to the top of the pot a couple times a year, and he grows great paphs. They're also one of the few orchids that don't seem to suffer from repotting, in fact they kind of enjoy it!   (Mar-17)


Encyclia Bulbs Yellowing and Leaves Dropping

 


Encyclia Bulbs Yellowing and Leaves Dropping


Q. My Encyclia cordigera suddenly, within a week, dropped two leaves and two pseudobulbs started to turn yellow from the apex to the base, with a brownish tone also. The affected pseudobulbs look shriveled. Right now there isn't any foul smell. What could be happening?

A. It looks like some sort of rot, as you obviously suspect when you say it has no foul smell. Are the yellowing/browning bulbs hard or soft where it is discolored? If the bulbs are hard, you would think perhaps Rhizoctonia root rot although that typically happens when the mix turns sour and of course your plant is on a mount. Are there any live roots attached to the dying bulbs? Your roots look good, so I'm guessing Rhizoctonia isn't the problem. It's probably more worrisome that the next two bulbs have leaves yellowing, so you would suspect that the infection, whatever it is, is travelling up the rhizome and travelling fast. The speed with which it's moving makes you think it's one of the water molds rather than Rhizoctonia, which is typically very slow to progress.
  If it is one of the water molds, also called black rot, your friend is your shears, you'll have to cut away all the infected tissue. You can pour hydrogen peroxide over what's left and if you have one of the good fungicides like Subdue that is labelled specifically for Pythium and Phytophthora, drench what is left of the plant with it. It's really a shame cause the new growth is so nice and healthy and should have been in bloom soon. (Mar-17)


Fill Tea Bags with Organic Fertilizer
 

Fill Tea Bags with Organic Fertilizer

Q. How do you fill your tea bags with the Purely Organic fertilizer? I put mine in seed trays open, fill all through a funnel and then close.

A. That looks like a good way. I like it when my Stepmom is in town and she fills them up for me. She just scoops up the Purely Organic with a 2 inch plastic pot and pours it into the tea bag. I got the large bags last year, but I like the size of your tea bags better.   (Feb-17)


Bulls Eye Spots on Leaves
 

Bulls Eye Spots on Leaves

Q. I grow phalaenopsis orchids indoors in Pennsylvania. I have some that have tiny lighter, round spots on the leaves that seem to have a dot in the center. I have sprayed them but it doesnít seem to make a difference.

A. I am a bit stumped, that bullís eye pattern of damage looks like thrips damage where the thrips pierced the leaf and the sunken spot formed around it, but I wouldnít expect thrips in your home in PA in January. Brook wrote back that leaf damage is not new and she suspected thrips from when the window were open in the summer, as she had thrips in the herb garden and in the potato fields.   (Feb-17)


Rehab or Discard Plant

 


Rehab or Discard Plant


Q. The leaf and plant look limp and it has dark spots and white fluffy things. Is there some way to save this plant, or should it be disposed?

A. You have several things going on. The white fluffy things are mealybugs, and they are very difficult to get rid of. For a household cure, you can spray the tops and bottoms of leaves and all leaf crevices with isopropyl alcohol each week, for at least a month. The ;leaf limpness means the plant is dehydrated, which means that it is either not being watered frequently enough or the roots have been damaged and cannot take up water, this often occurs when the potting mix starts to degrade. Youíll have to knock the plant out of the pot to check the roots to determine the problem. The browned and necrotic part of the leaf is dead, and this could have been cause by several things, like water pooling on the leaf, sunburn, etc. Whether you choose to rehab this plant or discard it, you may want to understand what caused the problems so you can prevent them from happening in the future. (Feb-17)


Too Long Phal Flower Spike
 

Too Long Phal Flower Spike
Q. This healthy phal keeps producing more blooms from the ends of the same spikes that had other blooms earlier. One spike now must be 2 ft long. What do I do, cut it or just keep letting it sprawl?
A. That is a decision only you can make. Some of the phals will just keep on blooming, but you enjoy the flowers less and less because they are presented poorly. By keeping the old spike, the plant doesn't redirect its energy into producing a new spike where the flowers might be better arranged. I tend to cut the old or unmanageable spikes down at the base rather than waiting for them to throw off one of two new blooms. The plant takes a little break from blooming and then forms a new flower spike that I can really enjoy. Other folks won't cut the spike if it has any flowers. If you decide to cut, put the spike in a vase and enjoy it for another week.   (Jan-17)


Thick Small Leaves on Phalaenopsis
 

Thick Small Leaves on Phalaenopsis
Q. A friend has many phalaenopsis rescued from her office and now in her greenhouse. Some have new leaves that are stiff, green, and very thick, but smaller than the older leaves. They look like they are on super steroids, whatís going on?
A. If the new leaves are smaller than the older leaves, your plant is telling you that it is getting less of what it wants than it used to get. I'm guessing it's purely a cultural thing, nothing to do with pests or diseases. She repotted them from moss into bark, and roots acclimated to the moisture retentive moss will not thrive in the drier bark mix. Some growers add maybe 10% long fibered New Zealand moss to the bark mix to make the environment more amenable to those plump healthy roots that grow in moss. If she repotted 6 months ago, there has been enough time to reestablish the root system, gently tug on the plants and see if they are firm in the pot. If not, knock one out of the pot and take a look at the roots to decide on a course of action, perhaps top dressing the pots with some moss or a monthly dose with seaweed or some other root stimulator can jump start root growth. That bark looks very dry, it may just be a simple case of watering more.   (Jan-17)


Yellowing Leaf on Dendrobium
 


Yellowing Leaf on Dendrobium

Q. I am fairly new to dendrobiums and I was recently given a Den. Mangosteen (Den. Dark Red x Den. Suzanne Neil). I repotted the orchid into bark with proper drainage and noticed the roots, while numerous, were white and some very thin and string-like. I watered and weakly fertilized after repotting since it was very dry. Some leafless canes were yellow at the tips, one of the leaves on another cane was starting to turn yellow and some of the leaved canes were also developing a yellow color at the junction between segments. I am not entirely sure if this orchid goes dormant or if itís sick.
A. That is a very complex hybrid you have. Its parentage is mostly phalaenopsis and spatulata section dendrobiums, neither of which require a winter rest, plus a dab of the dendrobium section dendrobiums that do. How much of which genes sorted into the plant you have is a big question mark. I'd guess it doesn't require a deep winter sleep but most dens slow a bit in the winter so you donít water or fertilize as much.
  As to the roots, it sounds like the roots were not in great shape when you got the plant. When you say very thin and string like, I think you are saying that the spongy velamen layer was absent and you saw only the wiry filament. Perhaps add a little root stimulator or seaweed when you water to help the plant recover from repotting.
  As to the yellow, many of the dendrobiums with this background lose the leaves on the older canes although they often continue to bloom from the leafless cane. Yellowing is probably not good but I think a more important diagnostic is whether the cane is hard or soft. When it starts to soften, that is when the plant is starting to go south. Sometimes water or dew can pocket on a new leaf causing it to be shed, or maybe the plant didn't have enough hydration to hold the leaf. I don't think I'd be overly concerned, there's no black marks or streaking so whatever is causing it is likely caused by some environmental condition. The rest of the leaves look healthy. Keep on doing what you're doing and just keep an eye on the plant. I bet the flower is going to be fantastic! (Jan-17)


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