Orchid Culture - 2023 Questions & Answers

Blackening New Growth

Q. I've noticed that new growths on some of my cattleya species have been turning black. Do you think this may be caused my fertilizer burn?
A. If you are growing outside or watering from overhead, it's possible that water is pocketing in the new growths above the papery sheath that covers the new growth, and then a bacterial infection destroys the new growth. The problem isn't with wetting the leaves, it's that a pocket can form between the emerging pseudobulb and the protective sheath, and water can easily be trapped in there. I either score the sheath or gently pull down the sheath to remove the pocket.   (Sep-23)

Sunburn and Bacterial Infection

Q. We had a blustery day and my shade umbrella fell down. I forgot to put it up the next day and I thought I had saved my phals from the sun. My local orchid FB page suggested that the problem was sunburn plus some infection. I’ve never seen the circular spots before with sunburn.
A. I think your local FB page is correct. That looks like the sun burnt those thick fleshy phal leaves and that created an opening for bacteria to invade the tissue. It probably happened really fast. You should cut away all the infected tissue to prevent the bacteria from reaching the crown of your plants. Good luck with rehabbing them!   (Sep-23)

Yellow Spots on Leaves

Q. I have a couple of orchids with yellow spots. One is an antelope type dendrobium, the other an Epidendrum nocturnum. I have Physan, Sevin, Banrot, and what used to be Bayer’s (in the blue bottle). Will any of these work or must I buy something like Pageant?
A. That looks like the beginning of one of the cercosporoid infections, so you'd use thiophanate methyl. It used to be sold as Cleary's 3336 or Thiomyl, and is one of the fungicides in Banrot. I find the fungus is almost impossible to get rid of; it's a blight on dendrobiums. You can spray for it, but once you see the damage, the fungus is inside the plant, beyond the reach of the chemicals. The best advice/hardest thing to do is remove all the damaged leaves and then spray. That chemical is also available as a granular, which is much easier to use. You can find it by searching for thiophanate methyl granular on https://www.domyown.com. (Sep-23)

White Spots on Cattleya Buds

Q. What are the bright white dots on the buds and inflorescence? It doesn't look like scale. How do I treat it?
A. Your plant is very healthy, exuding plant sap. Some little moldy something or other is growing on the sap, it is nothing to worry about. The blooms are going to be fantastic!   (Aug-23)

Some Thing on Vanda Root

Q. Could this be scale growing on the roots of my vanda?
A. I didn't think it was scale, but had no idea what the critter was. Corky took the plant over to the University of Florida, and they diagnosed the problem, oribatid mites feeding on the fungus and algae on the vanda root. From GardeningKnowHow.com: "The Oribatid mite is a type of soil mite that is commonly found in wooded areas where it often assists in the breakdown of organic matter. These mites occasionally make their way to patios, decks, container plants, or even inside homes. They are generally drawn to decaying organic matter such as leaves, moss, and mold." A couple of doses of Permetrol solved the problem. (Aug-23)

Leaf Spotting on Paphs

Q. I’m have a leaf spot issue on some paphs and probably should get something on them with all this wet weather. I don’t usually have any issues with fungus. Any recommendations?
A. A picture is worth a thousand words! I would say that's a cercosporoid infection, one of the leaf spotting fungi. According to Ann Chase, Daconil Ultrex, Pageant and Heritage are all highly rated for cercosporoids. Of course, fungicides usually will not cure an existing infection, just help stop the spread of the disease. You'll have to cut away the infected tissue to remove the source of spores. If it were my plant, I'd probably opt for the Pageant.   (Aug-23)

Leaves Have What Looks Like Scale

Q. My plant app suggested scale was the problem on my phals. I tried to rub the bumps off with isopropyl alcohol on a Qtip, but they didn’t come off. I had to scratch at them with my nail to get the bumps off, and then it seemed more like plant matter than bugs that came off. Then I came upon your website with an article about edema, is that what is on the leaves? There are spots of leaf splitting, could that be from underwatering? I also think I might have pushed the soil down too much when repotting.
A. That is definitely edema, caused by watering too late in the day or on a gray day. Leave the plants be, they'll be fine. The leaf splitting probably happened because it was growing quickly and the tender young leaf split. It looks like you've got the plants potted in bark, which a lot of people use. I haven't been too successful with bark, I use the long fibered New Zealand sphagnum moss or a Pro-Mix perlite blend. The question I'd ask is what were the plants potted in before? The phal roots become acclimated to the substrate they are grown in, and if they were in sphagnum moss when they came to you, they will have to grow all new roots to transition to bark. If they were in bark before, then bark is probably a good choice for you.   (Jul-23)

Sick Oncidium

Q. This plant was in the flood and the freeze, as well as two hurricanes, and the tag has disappeared. I think it has either Pseudocercospora or Guignardia, but I don't know which. Could it be both? My plan is to spray it again with Physan 20. Think I should toss it?
A. With everything that plant has been through, you won't know whether the fungal infection, whatever it is, is the primary cause of its decline or if the weakened plant was then more susceptible to disease pathogens. You can spray it, but sprays are generally protective, rather than curative. Very few fungicides will clear an infection, they simply protect the other parts of the plant from infection. If it were my plant and I wanted to keep it, I would cut away all the diseased tissue. It seems that the other end of the plant is much healthier. Cut away the disease, and then you can spray the remains. You won't have much left, maybe a single growth or two, so put it into a small pot with some high quality sphagnum moss til the plant gets healthy again. And if that's too much, toss it and get something that will give you pleasure when you look at it.   (Jul-23)

Orchid Blossom Midges

Q. I’m having a terrible time with orchid midges and can't find any information about how to control them. I’ve cut off all my spikes in my greenhouse but new buds are still showing signs. My agricultural supply people suggested Suspend Polyzone Insecticide, which I sprayed but it does not appear to have been successful.
A. I've never had midges, but they sound awful. There's not information about chemical control of midges, which lay eggs in the flower buds and the emerging larvae destroy the buds. Most articles just say cut off all the buds and bag them so the larvae can't escape to propagate. They talk about spraying the ground to kill anything that may be pupating there, but the insecticides can't reach inside the flower bud where the larvae are. My suggestion was to spray the plants and buds with Bt and consider a ground treatment with something awful like Cygon.
  If they are midges, you should be able to find the larvae in the flower buds. Otherwise, the problem is thrips rather than midges. An infestation with thrips is hard to get under control, but you can if you spritz the flowers and buds every three days for a month, spray the landscaping plants outside and nuke the area under the benches. Ann called a Pest Control Company and they came out and sprayed the ground outside the greenhouse, the shade cloth on walls, the floor and the orchids with straight Imidacloprid and repeated the treatment 2 weeks later. As of today, Ann is thrips free, yippee!   (Jul-23)

To Get Rid of Some Weeds, You May Need to Repot

Q. These two photos show why you can’t control these weeds by just pulling them. You must repot and remove the roots!
A. This Australian native is apparently very attractive in the wild. With the common names of Love Flower or Pastel Flower, Pseuderanthemum variabile is quite the nuisance in orchid pots. You can see why from Gordon's picture of the roots. If you just pull the weed and don't get all of the roots, it will simply grow back from the roots remaining in the pot. There are some chemicals that can be used to try to kill it, but sometimes you just have to knock the plant out of the pot and remove all the weed roots before repotting.   (Jun-23)

How to Repot

Q. Please tell me how to plant this plant I won at raffle last night.
A. Are you thinking of putting it in a pot or that clay basket in the corner of the picture? If in a pot, put some Styrofoam in the bottom and then push the oldest edge against the edge of the pot and hold it in place while you backfill. If in the basket, you'll situate it similarly, but you'll have to tie it into the the basket in 3 places to secure it so it won't move around while it's growing its new roots. Come to the repotting clinic at the library if you need any help!   (Jun-23)

Cattleya Not Rooting after Repotting

Q. I repotted this Rlc. Taiwan Good Life ‘Blessing Gold a year ago in May, and no roots have grown at all. It seems to be in just as bad shape as when I repotted it. I just took it out of its pot to photograph it (and its lack of roots). I’m feeling very discouraged about this plant. Should I give up?
A. That seems like a long time with no roots. You've got a new growth starting and in most unifoliate cattleyas, the roots would be soon to follow. While waiting for the plant to begin rooting, you could put it in a plastic bag with a little moist sphagnum or put it in in empty clay pot and spritz it every day or two. Once you see green root tips, you can repot. I looked up your orchid, and it has a lot of dowiana in its background, then I checked Bill Rogerson's article on when cattleyas root, and dowiana is one of those that roots after blooming, with the bloom season in midsummer. It is also one of those temperamental orchids that likes to be kept on the dry side during winter. So, that new growth forming does not mean that new roots are imminent. I think keep it shady and maybe think of doing the 'sphag and bag' until new roots form, and then pot up the front half of the plant. Unless you see active eyes, I would be tempted to cut off the back three bulbs so you'll have more room in the pot for new growth.   (Jun-23)

Pyschopsis Flower Bud Damaged

Q. Somehow, my second spike got damaged in its development stage. Her twin bloomed and luckily I have a new spike in the back coming! I think now I can cut the failed second spike. How far down should I cut?
A. I wouldn't cut the flower spike unless it browns and withers. Even if the flower bud is damaged, as long as the spike is green and viable, you might think about getting it to bloom from the next node down. Gently tug back the paper sheath protecting the node, and then just wait and watch to see if a flower bud forms there.   (May-23)

Oncidium Flower Spike Deformed

Q. This oncidium has bloomed in the past with many flower spikes. It recently put out spikes which have gotten deformed. They do not strengthen, are curling and tend to break off. None of the leaves are accordioned, so I don’t think it's poor watering. BTW The new shoots are very thick and look rather healthy, at least in circumference. Its just that they curl and refuse to strengthen up) It was in a south facing, filtered window for a long time. When it looked like the new spikes were going to be deformed, I moved it to a nearby east facing window with a full spectrum LED light, but that didn’t improve the situation.
A. The flower spikes grow towards the light, and sometimes a spike starts out under a leaf and then curls a little bit til it finds the light to grow towards. So maybe it did not respond well to being relocated from the south to the east facing window, although the deformity apparently started while it was still in the south window. I would move it back to the south window, where it apparently thrived. It is possible there is a calcium deficiency causing the spikes to not strengthen, but my gues it is likely mostly a light issue. (May-23)

What's Eating My Flowers

Q. Something has been snacking on the orchid flowers. Could it be a caterpillar, althought we have not been able to spot any, or any other insects. Any suggestions?
A. It could be caterpillars although you would think you would see some caterpillar poop, and it could be cockroaches, it could be snails/slugs but you'd think you'd see slime trails. The bigger the bites, the bigger the critter, so probably cockroaches or mice/rats would be my suspicion. If it were caterpillars, you would spray with BT, if it were cockroaches, bait with boric acid, there are various baits for snails and slugs and are traps/poison for rodents. Best of luck! (May-23)

Weeds in Orchid Pot

Q. Any thoughts on safe treatments for weeds other than mechanical removal?
A. Those weeds are tough to get rid of, even mechanically, because they've got such a long root system. There is a product with the active ingredient diuron that can be sprayed on the weeds and not harm the surrounding orchids. It is sold under many trade names, including Parrot and Karmex. Here's a link to an article with some suggestions.   (Apr-23)

Miltoniopsis Declining

Q. Could you comment on what might be the problem with my Miltoniopsis John Leathers? It has new roots and spikes. It has been with me for 5 years constantly blooming. Then these chlorotic leaf markings showed up. I have flushed media, switched to MSU in case it is a nitrogen deficiency and gave it a spray of Physan 20 as a precaution.
A. The questions that came to mind when looking at the pics were what potting mix is it in, when was it last repotted, can it be picked up by the leaves without it being wobbly in the pot, and is the leaf yellowing happening on the newest or the oldest leaves. Amal checked the roots which were declining in the degraded mix, and repotted in fresh mix, removing dead roots and pseudobulbs as well as seriously discolored leaves and then gave it a fungicidal treatment. If you notice a plant declining, knock it out of the pot to take a look at the roots, that often will tell you what your next step should be.   (Apr-23)

Over-potted Dendrobium

Q. My Encyclia Nursery Rhyme Genesis orchid will grow what appears to be sheaths. The "sheaths" get 1/4" in length before drying up. The orchid gets ~ 200 PAR of light, is potted in a sphagnum moss with a bit of standard orchid mix. The light sources are an east facing window and an overhead plant light. I let the potting mixture dry out to the point where moisture is barely noticeable before watering. I fertilize weakly weekly using a mixture of 1/4 tsp each of Epsom salts, liquid Cal/Mag and Jack's 30-10-10 in a gallon of reverse osmosis water. I have had the plant for 16 months. Also, I noticed a clump of pseudo bulbs growing in the air which I wiggled into the potting mixture without detaching. My question is why are the flower sheaths drying up?
A. The brown sheath surrounding the pseudobulb is a cataphyll, some people call it a sarong. It protects the growing pseudobulb from damage and after that it turns brown and paper and dies back, perfectly normal. Encyclias don't form a large flower sheath like other cattleya alliance plants. You'll see flower spikes emerge from the top of the bulb, and if yours stop growing after 1/4 of an inch, the plant just may not have enough stored energy to bloom. I have my encyclias potted up pretty tight in pots in a coarse, freely draining mix and they ultimately push their way out of the pot after 2-4 years. The pseudobulbs grow so closely together that you can accommodate several years of growth in what might seem to be too small of a pot. I wonder if that large pot and the water retentive mix you are using is too wet for the encyclias, and possibly that is why the bulbs started growing up and out of the mix? When I have questions about a plant, I often knock it out of the pot and take a look at the roots. You could see how well it is established in the pot by trying to life it by its vegetation, if it's wobbly in the pot, then the roots are not happy.
    The Jack's 30-10-10 fertilizer is an acid generating fertilizer, which will tend to become pretty acidic with reverse osmosis water that has no buffering capacity. We usually recommend that type of fertilizer for those watering with alkaline well water. For RO water, the 15-5-15 Peters Excel CalMag fertilizer works well. The Epsom salts should not usually be mixed with a CalMag fertilizer because the nutrients react (Epsom salts are compatible with the 30-10-10), but at the concentrations you are using you are probably not seeing that sludgy reaction.   (Apr-23)

Time to Repot Catasetum

Q. This plant was brought into the house for the cold spell. There is a new bulb and some roots starting to grow. Should I repot it now? Should I trim up the roots or just leave them alone and put it in a bigger pot with fresh media?
A. If you are going to repot it, this is the time to do it. I normally repot the catasetums every year into fresh long fibered New Zealand sphagnum moss. I typically discard the older pseudobulbs, particularly if they have any soft spots or reddish or brownish discoloration, and keep the youngest and perhaps the second year bulbs in the pot, cutting away most of the roots in the process.   (Mar-23)

Maxillaria tenuifolia Growing out of Basket

Q. I’ve got my coconut orchid in a 16” hanging basket with coco fiber, bark chunks and charcoal. She blooms every spring and grows out, filling the basket nicely but this is the first time she’s grown so tall in places and starting to arch out. Time to trim when weather allows?
A. I think they just like to grow up like that. I have two, one is an unruly mess and the other has a neater plant habit. Yours looks good, it looks like the mix is still in good shape, in which case maybe next year you can think about chopping it up, but for now I think I'd leave it be.   (Mar-23)

Brown marks and leaf drop on Trichoglottis

Q. I have a Trichoglottis atropurpurea (syn. brachiata) that I have had for 6 years. Nothing has changed in its growing conditions and it gets less light than my Vandas and has always liked it. Since November, I have leaves that regularly turn brown at the base then fall off and I have 3 areas where several leaves fell off and the stem is brownish/black but not mushy at all, no smell. Strangely enough, those black area generate growths of a new keiki and they seem to grow fine. Now I have the top leaf of every stem that has a brown marking. It is dry to the touch. Any ideas?
A. My best guess is that moisture pooled between the leaf and stem, maybe from heavy dews in the fall when the nighttime temps cool off, and started a localized rot. The blackened stem looks pretty rough, but perhaps it won't kill that section of the plant, from what I can see the roots still look good coming off that stem. The keiki forming at the leaf node makes sense, that's a survival mechanism. The brown marking at the top of the plant may have happened as that leaf was forming. For a bacterial problem, copper is your friend, but remove any severely affected leaf like the one in your first pic. Surprising that this happened suddenly if nothing else has changed, of course, who knows what was blown in from the Sahara from the Hurricane in October.   (Mar-23)

Keiki on Unhealthy Dendrobium

Q. I have a keiki growing on this dendrobium, the roots are healthy but the plant doesn’t look so good. Any thoughts greatly appreciated.
A. The roots need to be a little longer, at least 2 inches long, before you separate the keiki from the mother plant. When you repot, put it in a pot that seems too small, no bigger than a 2 or 3 inch pot. Dendrobium canes grow very closely together, and a small pot will accommodate the plant for the next 3 years or so. The pot the dendrobium is in now is probably too large for the plant. If you want to encourage faster root growth on the keiki, you can air layer it with sphagnum moss, wrap some damp sphagnum around the roots and tie it up with some mesh or pantyhose to hold everything in place.   (Feb-23)

Growing Indoors Under Lights

Q. Whatever this is, it is going through my collection. I am growing inside under lights. My first thought was thrips, so I sprayed with Captain Jack's Dead bug because it has spinosad. Today, I sprayed with Aliette. Suggestions, please.
A. The gray stippling and brown wounds look like the damage caused by mites. Do you have a loupe or magnifier so you can check for mites? Mites are a real problem for indoor growers, because they thrive indoors in the low humidity. They are arachnids, so most insecticides won't kill them. Avid is a good miticide if you have it. Or you can use one of the home cures, scroll down to the mites section for some ideas.   (Feb-23)

Top Heavy Vanda

Q. What can you do with a tall vanda that has roots at the base and none above that? If you just "top" it, and there are no roots presently, will it just die? Do you have any recommendations on how to stimulate roots up higher for the top section to be separate.
A. That vanda looks nice and healthy. You might try spraying seaweed or a stronger root stimulator in the leaf axils where you'd like the roots to form, say weekly. Or, wrap sphagnum moss with panty hose where you want the roots. (Feb-23)

Keikis on Cycnoches

Q. This Cycnoches Topaz Grande is my pride and joy, but it obviously thinks it’s dying as do I. One cane rotted off but the others seem to be quite firm. Do I just leave it do its own thing or do I somehow remove the keikis?
A. If your plants have time left in the growing cycle, I would cut the bulbs about half way between the nodes that carry the keikis and pot them up in small (2 to 3 inch) pots in good sphagnum moss and let them grow til dormancy hits, the nutrients in the pseudobulb will continue to nourish the keikis until their roots grow into the moss. Another alternative would be to get a shallow bulb pan with long fibered sphagnum moss and just bury the pseudobulbs half way into the moss so the keiki roots can grow into it. The bulbs will ultimately rot and you can pull them out while the keikis continue to grow. The keikis may continue growing through the winter, or they may go dormant. If most of your other plants have entered dormancy, it may be better to leave the keikis on until next spring.   (Jan-23)

Hard, Clear Bubbles on Phal Leaves

Q. There are hard, clear bubble shapes on my phal leaves. It doesn’t look like an insect. What could it be?
A. That's edema, like a water blister. It happens when you water late in the day when the air cools or the skies turn gray, so transpiration slows down and the water needs to be shed from the leaf so it forms these little blisters. It won't harm the plant. Here's a link to more information. (Jan-23)

Color Break on Cattleya

Q. Do you think this is virused? Where can I buy some test strips?
A. That looks like a nasty case of color break caused by Odontoglossum Ringspot virus (ORSV). Sometimes you can join a group that is ordering the test strips from Taiwan, or you can order from Agdia in groups of 5 to 25. Such a shame!   (Jan-23)