Orchid Culture - 2012 Questions & Answers
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!
Q. Can you please assist us in identifying this orchid?
A. The Cymbidium man Harry McElroy thinks that is the warm growing species Cym. aloifolium. It has pendulous racemes of flowers ranging from white with red flares to almost all red with some orange or yellow forms. The striped red lip and general flower form distinguish Cym. aloifolium from the somewhat similar Cym. dayanum.
Growing Phalaenopsis Type Dendrobiums
Q. I recently bought a Dendrobium Thailand Stripe. The care
instructions say no more than two hours of light per day. Some sites suggest a lot
of sun. I'm confused and need help. Now the
leaves are yellowing. I'm in the
northeast and keep the thermostat at sixty degrees.
A. Your Den. Thailand Stripe is one of the phalaenopsis type dendrobiums. You
grow them like cattleyas, lots and lots of bright, but not direct, midday
sun. If you've been giving it only 2 hours of light a day, you'll have to
acclimate it to more sun slowly to avoid sunburning the leaves. They like
to get lots of water in the summer and be a little drier in the winter, but
not dry. I water every 2nd or 3rd day in summer and every 5th or 6th day in
winter, but of course I have my plants in a very coarse mix that freely
drains. If yours are in a bark or coco mix, you'd water a little less.
These types of dendrobiums are very cold intolerant. They don't like to be
below 60F and of course they'd prefer to be warmer than that during the
daytime. You'll have to find a bright southern or southeastern window for
your dendrobium and just nurse it through the winter. Then, in the spring
after it warms, you'll find a nice spot outdoors under a tree where the
plant will get plenty of air and bright light and it will explode with new
growths, rewarding you in the fall (most likely) with flowers.
Spots on Phalaenopsis Flower Bud
Q. I have spots only on the buds of my new Phalaenopsis plant. Help!
A. I couldn't tell what the spots were. They didn't look like scale or sooty mold. I suggested that the bud should be gently wiped with a Q tip dipped in isopropyl alcohol as a precaution. Two weeks later Larry wrote that the spots were just the brightly colored spots on the bud visible before the Plaenopsis flower opened!
Black Spots on Oncidium Leaf
Q. A friend's Oncidium has developed a bad case of black spot on two or three leaves. It was left in a house which was shut up for several days with out light.
A. Those spots are some sort of a bacterial infection (probably bacterial brown spot). You can tell by the yellow halo surrounding the sunken black spot, similar to when you have a bacterial infection on your skin and get the red halo around the infected spot. Pour hydrogen peroxide directly on the spotted leaves and if the spsots continue to enlarge either remove the leaf or spray with the highly effective fungicide/bactericide copper (just don’t ever spray dendrobiums with copper).
Cattleya Dehydrated Due to Lack of Water
Q. I keep my orchids on a windowsill in a plastic pot inside a ceramic pot with stones on the bottom where I put water to create humidity. The orchid has no new roots or growth and is not very happy. I water every 3 to 5 weeks as I am scared the root will rot.
A. The cattleya looks dehydrated, probably because it is not receiving enough water. In the summer, I water every 2 to 4 days, maybe half that much in the winter. Cattleyas like to be outdoors in the spring through fall. They seem to grow much better if they get the day night temperature change, the fresh air and the bright light outdoors. If the cattleya is indoors during the growing season, it won’t grow as vigorously. The bark looks okay but you can tell by sticking your finger an inch or two beneath the top of the mix. If the bark starts to feel like dirt, it means it is degrading and when the bark rots, your roots will rot too. Start watering more, much more. Water thoroughly until water runs through the pot and then water some more. Then don’t water again until the mix is dry. Start watering every week or no less than every 2 weeks.
Orchid Cold Hardiness
Q. Tonight’s low temperature is to be 40F, can I cover my orchids or is it best to bring them inside? I have flowering dendrobiums and oncidiums.
A. Bring any orchids in bloom or in bud inside. Unless you are sure of your plant’s cold tolerance, you can use these guidelines. Your most cold intolerant plants are phalaenopsis type dendrobiums, phalaenopsis and vandas. They should be protected when temperatures drop below 55 to 60F. The majority of your other plants should be protected when temperatures drop below 45 to 50F. Cymbidiums, Dendrobium and Callista section Dendrobiums and the Aussie Dendrobiums should be protected when temperatures drop below 35F. There are exceptions of course, with some species and their hybrids tolerating lower temperatures and some actually enjoying cooler weather.
photo by Greg Allikas
Stake Emerging Phalaenopsis Spikes
Q. I am growing my first phalaenopsis that has its first spike. I would like to let it grow naturally wherever it likes. Is there a reason why flower spikes are supposed to be supported?
A. The reason you stake a phalaenopsis is to help it present its flowers to their best advantage. When grown in pots, you want the flower spike to orient itself vertically and then arch pendulously so the flowers will be well distributed in a shingled pattern. You stake to help the plant hold the weight of the flowers. In nature, the plants grow in the crotches of trees and the flower spike comes out more horizontally and then bends downward from the weight of the flowers.
New Plants on Phal Flower Spike
Q. I have an orchid that has grown quite tall. Additional leaves and roots have sprouted from the flower stem. The original stem from which the leaves and roots have grown now appears to be dead. I have been watering the upper roots along with the bottom, but it appears there are no viable roots in the bottom. Can I somehow cut the stem off and transplant?
A. Your instincts are correct, your mother plant is dead but the children are thriving. It’s time to cut the children off the spike and replant them. (Nov-12)
Watering Orchids with Ice Cubes
Q. I recently repotted my phals and am watering them with 3 ice cubes per week. Several of the bottom leaves on one of my healthiest plants have started to yellow and drop. What do I do?
A. NEVER use ice cubes to water your orchids. When you water your plants, use room temperature water and let the water flush through the pot and then water some more. When you water, water heavily. Then, don't water again until the plant is approaching dryness. It's not too unusual for a phal to lose a bottom leaf or two particularly after repotting, but if the plant is dehydrated from insufficient water, it will also drop leaves. (Nov-12)
Vanda Lower Leaves Yellowing
Q. I have attached a photo of a vanda we were fortunate to pick up in the raffle. The problem is that the leaves are rapidly turning yellow from the bottom up. Is it a problem? Is there a solution?
A. That may have been one of the vandas I just ‘topped’ so the plant is probably shedding the bottom leaves that it can’t sustain with the lower part of the plant removed. It should stabilize and make it through the winter and then start growing again in the spring. I don’t think it is diseased, just working on finding a new equilibrium. (Nov-12)
White Patch on Phalaenopsis Orchid Leaf
Q. I have two plants whose leaves each have a white patch. Can you tell me how to fix this and how to prevent it from happening?
A. That looks like sunburn. Unless you just moved them, the angle of the sun must have changed enough that it burned the leaves. You can take a clean single edge razor blade and cut away the damaged part of the leaf. You will have to move them so they don’t get so much midday sun. Not to worry, they’ll grow new leaves.
Oncidium Pseudobulbs are Turning Brown and Soft
Q. These reed stem orchids all have different flowers. I keep them moist and the leaves have grown well, though suddenly one of the plants has turned brown and soft and it is falling apart. They are potted in a dried out moss that has almost turned to dust.
A. I don’t think those are reed stem orchids, they are in the oncidium family.
Some look nice and healthy, but one looks like it’s suffering from rot. I’d knock that one out of the pot, cut away the soft brown tissue and repot whatever is left in a smaller pot.
If the sphagnum has turned to dust, it is shot and it will retain too much water.
Think about putting them in fresh sphagnum moss (always wet it before you use it for potting).
The sphagnum only lasts for a year or two, after two years it is rotten and once it rots, the roots will rot and things all go down hill from there.
Collar Rot in Phalaenopsis
Q. The rot started on the bottom of the crown that is under the potting mix and worked its way up to the center of the leaves. The leaf and adjacent root rotted, Is it a cause for concern?
A. The main symptom of Southern blight or Collar Rot is a rapid collapse and rotting of the roots, pseudobulbs and lower parts of the leaves. Roots, pseudobulbs, leaf bases and the lower part of stems turn creamy yellow. The affected tissue becomes brown (resulting from invasion by secondary pathogens), collapses and rots very rapidly. The disease eventually girdles and destroys the entire basal portion of the plant. Affected leaves yellow, wilt and die. If caught early enough, you can treat with a systemic fungicide containing thiophanate methyl (like Cleary's 3336 or Banrot).
Cattleyas Don't Flower
Q. I have some phalaenopsis that grow well and bloom twice a year. However my cattleyas are not growing well. It looks like they are very healthy and keep growing new leaves slowly. I use fertilizer every other week. I put all my orchids in the east windows which provide plenty of sunlight. Why do I only get one bloom in 5 years?
A. Your cattleyas need more light. An east window is perfect for phalaenopsis, but they are low light plants. Cattleyas require bright light such as from a southerly window to accumulate enough energy to put forth those beautiful flowers. Is there a place outdoors in dappled light that you can transition them to slowly so they’ll get more light?
Q. I got this phal to bloom, but the inner petals are not opening at all. Some of the older flowers have wilted and fallen off the spike. Have you come across phals like this one where there are only half opened blooms?
A. I think that is a peloric phalaenopsis, where the petals mimic the lip. It's genetic and the plant will always bloom that way. Some people love them thinking them attractive and some people hate them thinking they are deformed. All that matters is whether or not you like it.
Leaves Growing on Phal Bloom Spike
Q. A few months ago, I accidently cut off a blooming sheath from my
orchid. I stuck it in some water until the bloom died. Now I have many
new leaves that are starting to grow. Everything I read says it will
never reroot, but I hate to throw it away. Any suggestions?
A. Those are keikis, new babies, growing on the flower spike.
The plantlets must be using a reserve of food in the flower spike to power their growth. You can't remove the keikis until they get roots.
Perhaps you could get a flat and
put an inch or so of sphagnum moss in it and lay the flower spike on top of
it and see if the little plantlets will root. I can't say I've ever seen
keikis form on a cut phal spike before, congrats!
Brassavola digbyana Won't Rebloom
Q. My B. digbyana has beautiful color,
two new leads and 4 to 5 leaves as shown with what looks like a bud
starting but no sheath ever appears. I suspect it needs more light because it hasn't bloomed since I got it in bloom several years ago.
A. B. digbyana (or Rl. digbyana as it's now called) and
Brassavolas in general like the high end of cattleya light.
If it hasn't bloomed for you, the most likely reason is that it's not getting enough
light. It may be getting enough light to grow well, but not enough for it
to manufacture enough food to produce the beautiful fimbriated flower. Try
moving it gradually into more light. Insufficient light is the number one
reason why orchids don't rebloom.
Algae in Clear Orchid Pot
Q. I am seeing green stuff grow on the inside of the pot. Should I worry about this?
A. That’s algae growing inside the pot because the pot is clear. If it bothers you, you can drop the pot in a decorative pot that will block the light or occasionally pour some dilute physan or 10% pool algaecide through the pot (say 1 tsp/gal).
Stippling and Webbing on Orchid Leaves
Q. I have some problems with my phalaenopsis and dendrobiums.
I don't know if the problem is caused by some little creatures or not.
Can you help my plants?
A. I am afraid you have mites on your orchids. Try spraying upper and lower leaf surfaces with the home cure mixture of 1/3 rubbing alcohol, 1/3 409 or Murphy's Oil Soap and 1/3 water.
Plants can also be sprayed with a miticide like Avid, Talstar or Kelthane following label instructions being particularly careful to contact all the undersides of the leaves.
During warm weather, new generations mature every 6 days so repeat applications will be required, perhaps 3 applications at 4 day intervals.
There are some good tips on the website
with links to good articles.
Cattleya dowiana - Virused? How to Grow This Species
Q. This C. dowiana aurea has a great flower, but the plant is not a vigorous grower. The leaves have black splotches (ugly plant syndrome!) that make me fear virus. I've always heard that dowianas like to be grown on the dry side. What do you think?
A. Our future speaker Keith Davis, a North Carolina orchid hobbyist and hybridizer, answered my questions: It looks like virus, but could be microbial infection. Do you have or know someone who has one of those virus testing kits by Agdia you could use? (I did and it tested positive for virus). Even if it is virused, you can grow it and if you get a really good root system, it could outgrow the symptoms. Baskets with plenty of water and nutrients while active will put on a great root system. You ought to self it to preserve the genetics in case it dies. A dry seed pod will result in virus free seedlings.
Dowianas grow near the tops of tall trees, so they are the first to get wet when it rains, and also the first to dry out. When in active growth, they like a lot of water and food. I feed all my orchids at every watering just like in nature, low dose, but every time. The main thing on dowiana is to preserve the roots. Baskets are good because they dry out fast yet allow you to water frequently. You never have to repot in baskets if you use an inorganic mix. They also like a lot of light, more like C. gigas.
That selfing of C. dowiana 'Maku' that Carter and Holmes has came from me. It was a really great dowiana aurea and I selfed it so the genetics of that plant are preserved. Here is a photo of my daughter when she was small and two divisions of 'Maku'. It was a very good grower as you can see.
Den crumenatum - The Thunderstorm Orchid
Q. The mystery of Den. crumenatum, it blooms on the bare canes. Can you give me any cultural tips?
A. Josh Jones responded to this question: Commonly called the Thunderstorm or Pigeon Orchid, Den. crumenatum is very easy to grow with no rest period required. Having an unusual blooming habit, Dendrobium crumenatum flowers in response to a sudden drop in temperature (about 10 degrees) which mostly occurs after summer rains in nature. If this happens, expect the plant to bloom around 9 days later. Plants require intermediate to warm temperatures and medium amounts of light. It is found in Hong Kong, Taiwan, India, Sri Lanka, Andaman Islands, Myanamar, Thailand, Malaysia, Cambodia, Laos, Vietnam, Lesser Sunda Islands, Moluccas, Sulawesi, Sumatra, New Guinea, Christmas Islands and the Philippines.
Phalaenopsis Roots Outside the Pot
Q. This is a phal I am babysitting. I repotted it about 6 weeks ago and am concerned about the number of roots above the media. Do you think I should repot and remove some of the bottom stem?
A. I usually remove the bottom stem until the woody section is gone and the tissue is alive. Of course, if you do this you'll lose bottom leaves that would then be potted below the medium and those leaves look pretty good, though if potted deeper in the pot the plant would be better anchored and not have to be propped up. The fact that those roots are out of the medium is not in and of itself a problem because of course in nature they don't grow in pots and the roots wander where they want. I'd say knock it out of the pot and see what's happening.
If everything below the bark is dead, then I would sacrifice a few of the bottom leaves and drop it lower into the pot. If the existing roots look pretty good, I'd let it rock and roll. You'll get a good idea of what's happening if you just tug gently on the plant, if it's very wobbly in the pot, you can assume the roots are kaput.
Leaf Blight on Stanhopea
Q. This stanhopea hangs on a north facing balcony. The cattleyas are thriving in this setting and the stanhopea has developed a new bulb that has thrown a new leaf. Over the past 10 days I have seen brown dots, surrounded by a ring of yellow tissue, from which I conclude it is a leaf blight of some kind. Everything else in that same setting is happy and healthy – can I ignore this?
A. It is likely one of the fungal infections, perhaps Cercospora, though it does not matter which one cause you treat all the fungal spotting diseases the same way. You should probably remove the leaf with a sterile blade and then think where you can move the plant where it will get more air movement. I think a shady spot with wafting breezes is the answer. I just moved all my stanhopeas outside under the pergola cause I have problems with leaf spotting too and Penny and Viv seem to have better luck than I because they grow theirs out in the open air. From this I conclude that air movement for stanhopeas is critical. Also, Courtney says that 90% of orchid diseases are caused by some cultural problem, so it’s your duty to observe and make changes when you have an unhappy orchid!
Bottom Phal Leaves Yellowing
Q. I have lost two leaves that turned yellow but my orchid is still blooming. I keep it in the house facing the sun but I keep the house cold. We’ve had it about 3 months what am I doing wrong?
A. If you have lost the two bottom leaves, perhaps your plant is getting too much water. Your roots may be beginning to rot from suffocation and the plant may drop leaves in response. Your mix is starting to degrade and the phal needs to be repotted soon, though that will interrupt and end the bloom cycle. Drop the phal back in the pot and cut back on watering. Don't water it until the mix is dry to the touch an inch or so below the surface. You’ll have to find a good potting mix to use and then by the end of June, plan on cutting the flower and enjoying it in a vase for another week and repot. Here’s a repotting link.
Sunken Spots on Phalaenopsis Leaves
Q. I was given this orchid and started noticing changes on the leaves. I think it might be mites. Would you be able to diagnose the problem and also let me know how to treat it?
A. It sure looks like mites, probably flat mites. There are some pictures
of phals that look remarkably similar to your plant, just click on view more images of mites on orchids. Try spraying upper and lower leaf surfaces with the home cure mixture of 1/3 rubbing alcohol, 1/3 409 or Murphy's Oil Soap and 1/3 water. Plants can also be sprayed with a miticide like Avid, Talstar or Kelthane following label instructions being particularly careful to contact all the undersides of the leaves. During warm weather, new generations mature every 6 days so repeat applications will be required, perhaps 3 applications at 4 day intervals. If nothing else, start spraying the upper and lower leaf surfaces with a dishwasher soap solution.
Powdery Substance on Orchid Leaves
Q. My orchids have developed a powdery substance on the leaves, which started on the underside and then spread from there. What is this, and how do I treat it?
A. You have mealybugs and lots of them. You can use a toothbrush or a Q tip, dip it in isopropyl alcohol and wipe them all away, or put a spray head in an alcohol bottle and spray, you’ll have to do it weekly for say 3 weeks to get all the emerging babies. Alternatively, you can drench your plant with one of the Bayer imidacloprid products. Mix up a solution and water your plant thoroughly, the systemic insecticide will be drawn into the plant through the roots and kill the mealybugs from the inside out. Get ‘em quick before they suck all the plant sap from your orchids!
Minute Spots on Top and Bottom of Orchid Leaves
Q. My orchid is two years old it blooms twice a year. I have noticed minute spots on the top and bottom of the leaves. The substance is also sticky and leaves the sticky residue on the window sill. How do I get rid of these spots, how do I care for my orchid so this does not return.
A. That is scale. The mother scales are the conish looking large brown dots. She lays eggs under the armor and the juveniles crawl away to set up housekeeping. The scale is on both sides of the leaf and is pretty extensive. The sticky stuff you are seeing is honeydew, which is plant sap. The scale suck the sap out of the plant and that’s what you’re seeing on the windowsill. First, get a Q tip, dip it in isopropyl alcohol and wipe both surfaces of the leaf to remove the scale. Then there will always be some left in the crevices and possibly in the roots. If you have the Bayer imidacloprid product, you can drench the plant (mix up a pint solution and water the plant). It will soak up from the roots throughout the plant and kill the remainder. You can also put the isopropyl alcohol in a spray bottle and spray all the surfaces and crevices weekly for say 3 weeks to catch the young ones. Any plants close to this one should be looked at too because the scale will go from one plant to another.
Q. Can you help me identify this orchid and give me any tips about growing it?
A. That looks like one of the terete vandas, possibly a V. Miss Joaquim. They like to grow in very very bright light and, like all vandas, need plenty of water, fertilizer and air circulation.
Orchids Won't Bloom
Q. I have several orchids that bloom without fail every year, but some do not, or do so very poorly. They are in a south facing window and get plenty of light all year long. In the summer the window is shaded by the lilac outside, so there is not overly strong light. They have been in this position for two years. Any advice on how to induce flowering?
A. The orchids look happy, particularly the phalaenopsis. Healthy orchids that don't bloom are usually not getting enough light, particularly the dendrobium on the floor which is receiving the least light of all the orchids. The lush green color of the dendrobium leaf also suggests it needs more light. Perhaps you can find a location outdoors to summer your orchids under a tree or on a southeast facing porch where they will receive a higher light level, particularly those orchids that like bright light. They should be acclimated to the higher light level slowly to prevent leaf burning.
Black Spots on Orchid Flower
Q. I think I have Botrytis petal blight on one of my orchids. The spots were there when I bought the plant 5 months ago and there has been no worsening. The other thing is there are two secondary spikes with no buds or flowers.
A. You may have a spot or two of Botrytis. Try wiping it off with a Q tip dipped in isopropyl alcohol. If you've had the plant for 5 months and the Botrytis hasn't spread, the fungus is not active. As a precaution, you could spray the flower with a solution of baking soda and water (say 1/2 tsp per quart). The secondary spikes will apparently do their thing when they're good and ready! Beautiful plant!
Spike Growing Under Flat Leaf
Q. I have an orchid that has started growing a new spike that is about 2 inches long. The spike is growing under one of the bigger leaves. Will it grow around the leaf or do I need to redirect it once it is long enough with a small stick?
A. The spike will grow around the leaf though you can redirect it slowly and gently if it doesn't work its way around. Once it's about 6 or 10 inches tall, you'll start staking the spike to get it to hold its flowers well.
Potting Mix Like Soil
Q. I acquired a zygopetalum from a co-worker. I have no idea what the roots looks like. The mix appears to be super fine almost like soil and I do not know when it was re-potted last. Anyway, my thoughts are to re-pot this orchid ASAP into a new mix.
A. Trust your instincts Luke! Most definitely the plant need to be repotted, that bark is rotting and turning into 'soil' and when the potting mix rots, the roots will rot. Knock it out of the pot, if the roots are dark and soft, they're rotting. You can try to revive the plant by potting it in a small pot in sphagnum moss until the root growth resumes, then you can move it into a larger pot with your mix of choice. Peat based soilless mixes like ProMix are often used for Zygopetalums.
Scorched Leaves on Phal
Q. Is the Doctor in? What is wrong with this plant and what do I do about it? Poor old thing, it flowers again and again but the leaves look bad.
A. That is sunburn on your phal. You can cut off the damaged part of the leaf with a sterile razor blade and move it into a shadier spot.
Round White Fuzzy Spots on Leaves
Q. My orchid plant has developed small, round, fuzzy spots on the leaves and then the leaves turn brown and die. Could this be an insect even though it has been kept inside? Is it treatable?
A. That is scale in the crawler or juvenile stage. You can physically remove them with a hose end spray set to flat and water blast them off or put a spray nozzle in an isopropyl alcohol bottle and spray the leaves to kill the scale. Contact insecticides like Malathion or Orthene can be used but probably require 2 or 3 treatments. The Bayer imidacloprid products can be used as a spray or a drench (water the plant with the insecticide solution) and they are systemic so will have a longer lasting impact. This spreadsheet
contains application rates.
Ortho Sprayer for Fertilizers and Chemicals
Q. How can I easily mix up my water soluble fertilizer to apply to my orchids?
A. Use an Ortho sprayer to apply fertilizer, pesticide or fungicide to your orchids. It’s simple to use if you remember that the total number of ounces in the sprayer divided by the application rate in oz/gallon will equal the total number of gallons that you will make. Say you want to make 2 gallons of pesticide to spray on your orchids. You will add the pesticide from the label instructions for 2 gallons of water. Then use the highest dilution rate, say 8 oz per gallon, set by turning the red dial to 8 oz. You'll spray 8 oz/gal for a total of 2 gallons, so you'll fill with water to the 16 oz line on the side of the sprayer (8 ounces/gallon times 2 gallons equals 16 ounces).
If you use a dedicated sprayer for fertilizer application, you can just make up the solution and spray until the solution is gone. Say you want to fill the solution up to the 32 oz line in the sprayer and you want to use an application rate of 4 oz per gallon. You will add the fertilizer for 8 gallons of solution (32 oz divided by 4 oz/gal equals 8 gallons). If you apply fertilizer at ¼ tsp/gallon, you would add 2 tsp of fertilizer, fill with water to the 32 oz line, turn the dial to 4 oz/gal and then go feed your orchids!
Sticky Dew on Flower Spike
Q. My orchid sends up a stem and the tip end develops this sticky dew that eventually causes the stem to rot and die. The last time it happened, it killed the whole plant. What am I doing wrong?
A. The dew is simply plant sap, the sugary liquid the plant uses as fuel. Sometimes an exuberantly growing plant will exude the honey dew. Sometimes, however, there is some insect that has pierced the plant to suck the dew from it, like scale or mealybugs. Look closely at your plant to see if you see any white blobs anywhere, on the flower stem, between leaves, etc. If you find any, you can wipe them away with a Q tip dipped in isopropyl alcohol. The exudation of dew in and of itself should not harm your plant, but insects feeding on it will.
Brown Sunken Spots on Orchid
Q. I was looking at your excellent site and saw the Q & A.
Attached are two photos of a disease or pest I have on an orchid, along with another picture showing it during happier days.
Any assistance you could give diagnosing it and advising on treatment would be greatly appreciated!
A. That looks like a beautiful Den. aggregatum. It looks like it has bacterial brown spot, an advanced case on the lower leaf with the advancing yellow margin, and a younger infection on the upper leaves where there are sunken brown spots. To stop the spread of disease, cut away the severely damaged leaves with a sterile razor blade and then pour full strength hydrogen peroxide over the rest of the plant.
It's possible the plant got too cold or there was not enough air movement, so the infection set in. Now that it's spring, it should start to grow and grow new pseudobulbs, so it will recover by the end of the summer.
White Deposits on Orchid Roots
Q. This orchid has flowered wonderfully but now has this white deposit on the roots. I think it is a good time to repot it, there are only two flowers left on the stem. Should I treat the plant with chemicals too, and if so what?
A. Mealybugs have been feasting on your roots. Use a water jet to remove all the sphagnum moss from the roots as well as
any white masses. Then spray the plant, top to
bottom with an insecticide for mealybugs (one
containing imidacloprid would be great). Here's a good article on
How to Grow a Gift Orchid
Q. A friend gave me 3 orchid plants just before Thanksgiving. They were doing fine until about a week ago and then they started wilting. All the flowers are off and I know that orchids do come back. What sort of care do they need to rebloom and when might they bloom again?
A. You have phalaenopsis orchids. They bloom for about 3 months each year. After blooming, you'll cut the bloom spike at the base of the plant and repot them into fresh mix. Then find a nice shaded place under cover outside for them to grow in the summer. Water and fertilize them regularly. You'll leave them outside for the first cold snap around Halloween, the cold weather will tell your plant it's time to start initiating the flower spike. Then move them inside to an eastern or south facing window for the cold weather. You'll see spikes by Xmas and the flowers should be open by Valentine's Day. (Apr-12)
Elongated Discoloration on Cattleya Leaf
Q. I have large areas of discoloration on my cattleya. What is the problem?
A. That is bacterial brown spot (caused by Pseudomonas or Acidovorax). On the upper side of the leaf, you see an elongated reddish discoloration. The sunken bacterial spots have coalesced and are clearly visible on the underside of the leaf. That infection is fairly extensive, so cut off the affected leaves to at least an inch below the discoloration and pour some hydrogen peroxide over the rest of the plant. Spraying with a copper fungicide / bactericide would be even more effective. (Apr-12)
Brown Nodules on Orchid
Q. I came across your very informative webpage. Attached is a picture of one
of my orchids with small brown modules on it. They are easily removed. Seems too big for mites?
A. That is hard scale, you can remove it with a Q-tip and isopropyl alcohol
or you can put a sprayer in the alcohol bottle and spray the whole plant. Here is a more information.
Flower Spike in Middle of Phalaenopsis Crown
Q. My phalaenopsis has a flower spike coming out of the center of the plant rather than at the base of the leaves. Is there something wrong?
A. Your plant will probably cease to grow new leaves from the apical crown of the plant after this spike is finished. Some people believe this atypical flowering is from too much light or usage of systemic insecticides. A plant that does not resume normal growth will usually throw one or more new plants or keikis from the base of the plant, so don't throw it away. Until it does produce new plants, continue to treat it in a normal manner.
Transparent Spots on Phalaenopsis Orchid
Q. Some of my phalaenopsis have developed spots. They’re transparent from the bottom and raised on the top. I haven’t seen any crawlies, fuzzies or webs. There is a small pinhead in the center of each blight. This has developed only over the last four/five days or so. Can you help?
A. I'm pretty sure it's edema which is caused by the plant absorbing more water than it needs or can transpire. This typically happens during cooler weather when the water demands are lower and you water late in the day or on a gray day. The leaf will just have that blister on it until it drops of natural causes.
Bud Blast on Phalaenopsis Orchid
Q. I have a small phalaenopsis that has bloomed for a couple of years. I just got two new spikes with buds on them and then they got droplets of sap on them and are now withering. The ends of both spikes and the buds look like they are going to die. Can they be salvaged or should I just cut them off?
A. The otherwise healthy flower spike looks like it rotted right below the flower buds. The bottom and top of the spikes both look healthy, it looks almost like someone squeezed the life out of the middle of them. It’s possible that a sucking insect like a mealybug or thrip caused the bud blast and the plant sap is left from their activity. It’s also possible a fungus like fusarium caused the rot. At this point, I'd cut the spike at the base of the plant, repot it in fresh mix and get it reestablished so it'll grow over the summer and flower during the next bloom cycle. It's a shame, and a double spike too!
Cattleyas Outgrowing Their Baskets
Q. I have two nodosas, one in a 5" basket and the other in a 3" plastic basket. Both are overgrown in their present containers and pretty heavily budded. I might just put the smaller one in a larger plastic basket without any trimming, just another layer of media (love that wine). The larger one looks impossible to dismantle without serious damage. What to do?
A. Just drop them both in larger baskets. You can get plain wire baskets and drop them in, basket and all. If you want, you can line the basket with screening material, plastic fencing material or shadecloth to hold some potting media between the two baskets.
Don't disrupt the roots, they look way too happy
just the way they are!
Sunken Brown Spots on Phalaenopsis Orchids
Q. I'm seeing lesions on the leaves of some phalaenopsis that look like black rot. I'm in a panic given all 6 of my plants are in spike. Will fungicides damage the plant while in spike?
A. That is bacterial brown spot, the large spot is an advanced case and the smaller spots are new infections.
Pour some hydrogen peroxide on the sunken spots. If they don't enlarge, you will have killed the active bacteria.
If they do enlarge, you may have to cut away the damaged tissue. The hydrogen peroxide will not harm your flower spikes.
This disease is a major bacterial problem affecting phalaenopsis, here is a link for more information.
Q. Do you know the name of this orchid? This is its first bloom for me.
A. That is Dendrobium anceps. Grow it with your cattleyas.
Cold Damage from Proximity to Window
Q. What is the translucent spot on my dendrobium plant? I moved the plant away from the window to a cooler room.
A. It looks like the discoloration is on the upper, younger, more tender leaves that would be the first affected by cold. If it is cold exposure and the leaves are water soaked, it's possible that some sort of secondary rot may form. If it does, cut the leaf about an inch below the discoloration and pour hydrogen peroxide on the remaining leaf parts. The good news is the dendrobiums are very hardy orchids and will recover quickly.
Dendrobium Leaves Yellowing
Q. My dendrobium had seven spikes blooming under a tree this fall. Now all the leaves are yellowing and dropping, why?
A. Many dendrobiums are tolerant of the cold, but not the phalaenopsis type. They don't enjoy temperatures below 55 or 60. If they get colder than that, the leaves will yellow and drop. The good news is that the plant will perk up again in the spring.
Salt Encrustation on Clay Pots
Q. I bought a lot of used orchid pots and have not been able to remove the salt encrustation, how can I remove the white lime scale from the pots?
A. All pots should be soaked in soapy water and scrubbed to remove roots, potting mix and other detritus and then disinfected by an overnight soak in a mix of bleach (10% bleach or 9 parts water to 1 part bleach) and pool algaecide (2 tsp/gal if 10% strength) followed by a second soak to dissolve the chemicals. An hour bake in the oven at 400 degrees will kill any virus.
- Dishwasher. If the pots still have visible white stains, run them through the dishwasher with twice the normal amount of soap. The heat and soap will draw the salts either out of the pot or to the outside edge of the pot. Try scrubbing any residual salt from the pot.
- Mild Acid Soak. If the pots still have visible white stains, try an overnight soaking in a mild acid. Use white vinegar in whatever concentration you are comfortable handling, either a pure or a diluted (10%, 25% or 50% vinegar) solution. Scrub any residual salt from the pot followed by a second soak to dissolve the acetic acid.
- Nuclear Option. If salt encrustation is still present, consider admitting defeat and replacing the pot because the next alternative is the nuclear option. It involves a concentrated acid soak using muriatic acid, either pure or diluted (10%, 25% or 50% muriatic acid) followed by a fresh water soak to remove the acid from the pot.
There are many safety and environmental hazards involved with handling muriatic acid, so be prepared to follow all label precautions, use gloves, goggles, etc. as well as have a disposal plan because the acid is highly corrosive and foams excessively when you try to neutralize it with limestone prior to disposal.
Muriatic acid represents a potential threat to you, your pets and your environment that can be avoided by simply replacing the pot.
Lower Phal Leaves Yellow and Drop
Q. Some of the lower leaves of my phals are yellowing. I know this happens often right after repotting, but these phals were reestablished, so what’s happening?
A. I think that is Collar Rot, or Southern Blight, caused by the fungus Sclerotium. In phals, the base of stem turns light yellow, later dark brown, and the infection spreads to roots and leaves. White fungal growth can sometimes be seen on stems. There is a rapid collapse and rotting of the plant. Isolate it from your other plants, spray the surrounding area and plants with pool algaecide and drench the infected plant with a thiophanate methyl solution (Cleary’s 3336 or Banrot).
Mealybugs on Paphiopedilum Flower
Q. I have mealybugs on some just in flower paphs. They are all over the flower. (a friend gave me spray with alcohol, water and soap but told me not to spray the flower). Now what?
A. Use a Q-tip dipped in alcohol to delicately kill the mealybugs on the paph flower, and then your friend's concoction can be sprayed on the flower stalk and in all the paph crevices. They must be in between the leaf fans at the base of the plant and crawling up to dine on the delicious flowers, so really spray in between the leaves and in fact drench a little in the mix cause they can hide there too.
Q. I am trying to cope with this huge Den. spectabile. It was repotted last year and though it didn't seem to send out any new roots, it has 5 new shoots on it and I am wondering if I can cut off some of the old canes that look awful. I had it outside most of the summer and the old leaves have brown spots and edges on them (no bugs that I can see) and the new leaves are fine. Will it hurt the plant to cut off some of the old canes? The buds where the blossoms grow out seem to be old and dried up. Any advice?
A. If the leaves look diseased, you can cut them off, but leave the canes as this is where the plant stores energy and water (think of them as humps on a camel). You can remove the canes if they are soft or withered, otherwise leave them on, particularly because this dendrobium will bloom from old as well as new growth. The Den. spectabile blooms in the March time frame. If you've got 5 new leads it should be healthy and happy. Be patient, give it a ton of light and plenty of water and keep your fingers crossed!