Orchid Culture - 2020 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!
Spots on Vanda Flower
Q. I recently purchased some more orchids (a recurrent problem) and one was a blooming vanda that had questionable spots on the flowers. I wasn’t going to buy it as I was worried about Botrytis but I broke down and bought it anyway.
A. I think what you are seeing is edema on the flowers, in which the spots are raised and look a little corky. Edema is like a blister when the plant absorbs more water than can be shed through transpiration, so it blisters. It happens more on leaves than flowers. It happens when you water late in the day and the nights turn cool or when you water on a gray rainy day. It doesn't really harm the plant.
Q. This explains my dead Cattleya! And we aren’t even in the rainy season! Lesson learned…just because the water is running out of the clay orchid pot, it doesn’t mean that it’s draining. I suppose the remedy is to use clay pellets or sponge rock in combo with the power plus?
A. Looks like a nasty case of snow mold. The SAOS cattleya mix is something like 30% clay pellets, 30% coarse Orchiata bark, 30% sponge rock and 10% charcoal. Even so, occasionally you'll get snow mold after several years in the pot and it will smother the roots. Good that you found it, you can just remove all the bark from around the roots and repot.
Q. Is the stem of this orchid rotting? If not, should I put it into the medium?
A couple of spikes are growing, but she dropped two leaves last few days. I repotted her about 2 to 3 weeks ago after I noticed that one of the leaves was turning yellow and the sphagnum moss was turning black. If the stem is rotting, I wonder if I should cut portion of the stem and/or spikes to save this orchid. Please advise.
A. Phalaenopsis are monopodial, which means that they grow up on a vertical stem, getting new leaves at the top and losing leaves at the bottom. With the new leaves and stem, come new roots growing from the new stem. With the losing leaves at the bottom, the stem becomes woody and the bottom stem and roots ultimately die. Some repot phals every year, some every 2nd or 3rd year, depending on the condition of the potting mix and how far out of the pot the plant has grown.
If it were my plant, I would get some root stimulator, some long fibered New Zealand sphagnum moss and an empty pot. Cut the stem below the last aerial root and also cut the two flower spikes off. Spray the stem and the roots with the root stimulator. Then, wrap the stem with some good sphagnum moss, and drop the plant into the pot, placing an inch or two of styrofoam peanuts at the bottom and leave the rest of the aerial roots open to the air in the pot. You can mist, water the plant every other day or so while you are waiting for new roots to branch from the aerial roots and new roots to form from the upper part of the stem. You can then start backfilling the pot, a handful at a time, with your phal mix of choice.
Lower Part of Paph Unhappy
Q. I have several paphs that are doing well except for a few.
The upper plant seems healthy but the lower part had some past problems.
Should I cut off weak leaves and plant deeper in the pot?
A. Follow your instincts. The older part of the plant looks tired, cut away damaged leaves and degraded roots below the soil line, and repot it, and yes deeper in the pot. Clean up the plant, spray the stem with a root stimulator, let it dry and then repot. Think about your potting mix, are all your paphs in the same mix and if not, do some do better in one mix or another? Jim Krull at Krull Smith told me to add like 5% ProMix into the mix for more water retention. Courtney also top dresses with Dolomite.
Orange Crawling Creatures
Q. Do these little orange crawling creatures look familiar? They are an infestation.
A. Those are aphids. I get them on my garden plants, particularly the milkweed. In the garden I would just knock them off with a spray from the hose, but on my orchids I'd be tempted to spray with isopropyl alcohol or one of the pesticides. The problem with aphids is that they can have broods of 60 to 100 offspring every day, so they can be present in enormous numbers. I would suspect that there is some plant in your garden that is infested, and some have just moved over to the tender new growth on the catasetum. Search out the mother lode and destroy!
Q. I made this basket to repot my stanhopea, and I was thinking metal baskets may be a better (and cheaper) alternative to the usual wood baskets for my other basketed orchids, with a liner for containing the medium, of course. Is there any downside to doing that?
A. If there is a problem, I don't know about it. That is what I use for stanhopeas. I put the stanhjopeas on a thin layer of sphagnum moss with no liner. If you use a coarse media, you can use a thin layer of coconut fiber, but be careful using the cocunut liners they sell for wire baskets cause there is a thin layer of plastic in the middle that will prevent the blooms from emerging through the bottom of the basket. Barney Greer's book The Astonishing Stanhopeas says some of the Aussie growers even use four sheets of newspaper as the liner.
Phal Leaf Yellowing
Q. The leaves on my phals are suddenly turning yellow starting at the outer edges, what gives?
A. It looks like you are getting some sun bleaching, is that getting more light than it used to, with the longer days and increasing sun angle? And is it getting enough water and magnesium?
Ursula responded saying that the changing sun angle was causing the yellowing, problem solved! (May-20)
White Cottony Stuff on Vanda
Q. Could this be scale on my vanda?
A. That looks a lot like the tent caterpillars we get in our trees. The caterpillars weave a silken tent around them to protect them from bird predators while they devour surrounding leaves. I suppose it is just one of the hazards of growing plants outdoors. You should remove and destroy the nest and give the vanda a good wash with your hose end sprayer, and perhaps spray it with isopropyl alcohol. That is one healthy vanda you have! (May-20)
Q. This Clowesia is way in need of moving on to a bigger pot. Should I get rid of some of the old roots or just break them apart a bit?
A. Those roots look past their prime. I would cut them all away and then repot. Fill the bottom third of the pot with styrofoam and then interlayer time release fertrilizer with your potting media. Don't water until the new roots reach the bottom of the pot and the top growth is about 5 inches tall and unfurled. (May-20)
Sunken Spots on Dendrobium Leaves
Q. My dendrobium has developed spots on the leaves and I'm unable to identify the cause. I have been spraying with a systemic fungicide.
A. I would say that is bacterial rather than fungal, particularly if it happened pretty quickly. Copper is a very effective bactericide but of course you can't use it on dendrobiums because they are so sensitive to it. You can pour or spray the leaves with a fresh bottle of hydrogen peroxide. There are not many great options for dendrobiums. The systemics you are using are good fungicides for the leaf spotting fungi, but not for bacterial infections.
The question is, how did the bacteria get a stronghold in the plant. Low air movement and excess leaf moisture are conditions conducive to bacterial blighting, particularly if you are growing outdoors where the plants are watered by Mother Nature, so the leaves are wet at night.
Center of Cymbidium is Dead
Q. I am located in Melbourne, Australia. When my orchids bloom mainly in our winter, I get a healthy number from each. However, there are a large amount number of dead looking growths in my pots. Should I be re-potting to remove them or leave things as they are?
A. Harry, the Cymbidium Man, advised Nigel to repot: If cymbidiums are not repotted every 3 or 4 years, the center part does tend to die and should be discarded when repotted. Potting media tends to break down and decay over time and encourages rotting of the plants as well.
Remove all rotten material
including roots. Pots should just large enough to allow for 2 years growth.
I like to divide my plants when I repot and pot two or three
good growths and a nice firm back bulb. Two years growth for a division is 2 inches between the plant and pot rim all the way around.
Not sure what material they use for potting in Oz but fine bark should be good, like the Pinus radiata bark from New Zealand.
Some of the Australian growers I know have mentioned that they use it.
Black Streaks in Flower
Q. What is causing this flower blighting? The white cattleya flower opened in perfect condition and developed the black streaks after a few days, and the pink cattleya is starting to show some streaking. These plants are being boarded and are now in a more humid environment.
A. When you get that necrotic streaking in the flower about a week after it opens, and if it seems to follow the veining in the flower, I would be very very afraid that it is virused. If it is, I would suspect it is brown necrotic streak which some believe is caused by a strain of Cymbidium Mosaic Virus and others believe is from a dual infection of CymMV and Odontoglossum Ringspot Virus. The white cattleya is almost certainly virused. The pink cattleya may just have some bacterial blighting, but if in a few days that necrotic streaking appears through the midribs, then you would be afraid of virus. Do you have any test strips to verify whether or not they are virused?
What to Do with Aerial Roots
Q. I have a small potted Vanda that I hung on the east side gutter outside in a basket about 2 months ago. When I watered her this morning, I noticed all of these tiny black spots all over her leaves. She's been getting rain water and lots of breeze. Is this fungal, bacteria, virus, or something else?
A. Those spots are pigmentation from the vanda getting nice bright light, sort of like freckles from being in the sun. The spots should be reddish purple rather than black, and they should not be raised or sunken. I think it looks great, and should be a very interesting hybrid whenever it blooms!
Ground Orchid in Container
Q. I have recently bought a ground orchid online which came in a small plastic pot, which after I transferred it in to a bigger pot. Is it absolutely necessary to plant a ground orchid in to ground only and not in the pot?
A. I don't think terrestrials have to be planted in the ground, but I think they should be potted in a peat based mix rather the coarse mix you would put an epiphyte in.
Pod with Coco Coir
Q. My phal has fungus gnats so I removed some of the media and found a bunch of mushy gunk inside the pot. There as a sort of pod filled with coco coir which seems to be contributing to the mushy gunk.
What should I do?
A. When the bark rots like that, it will also rot the roots. If it were my plant, I would get a hose end sprayer and set it on jet, turn the pot upside holding the phal in and jet away as much of the potting mix as possible, all the mix that comes away without too much pressure. Jill wrote back that she jetted all the material away and found the 'pod'. Apparently, when the growers first potted up the phal, they put the seedling in a little plastic pot filled with oasis or coconut and when the plant got larger, they just slip potted it by dropping it into a bigger pot and backfilled with bark. The inside pot will always stay too wet if you water the bark the way bark should be watered, and root rot is the inevitable result. After Jill removed it and jetted away the rest of the potting mix, she added fresh mix with a minimum of disruption to the roots.
Phal Leaf Detached from Stem
Q. I was away for the weekend, and upon my return found a very sad white Phal. She had 2 very long leaves. As I was taking the pics, one just detached seemingly from the crown. Help!
A. That looks like Collar Rot, also known as Southern Blight, one of the devastating stem rots. You can see the fungal bodies on the close up of the stem. Scroll down the SAOS website Disease page
to the Collar Rot section to read about it.
The plant is probably beyond saving.
Your only possible hope, and a slim one, is to drench the pot with some fresh hydrogen peroxide (unless you have something like Pageant) and then keep the plant on the dry side and see if a basal keiki appears. However, the tissue from which the basal keiki would grow is what is infected with the fungus, so if it were my plant, I would discard it and remove the source of inoculum from the growing area.
New Growth at Top of Pseudobulb on Miltassia
Q. This Mtssa. Chas. Marden Fitch looked like it was going to be a spike, but instead of flowers it looks like a new growth. The top of the pseudobulb also looks like it is sprouting another new growth. Any ideas?
A. I have had oncidium alliance plants form keikis from the top of the pseudobulb on some occasions, but don't believe I've ever seen one form at the end of the flower spike like yours has and like often happens with Phalaenopsis orchids. It sounds like a teenager hopped up on hormones!
Leaf Damage on Dendrobium
Q. Does the mini-dendrobium have thrip effects on it? Do I remove the infected stalks with deformed leaves and treat the rest of the plant? There are new leaves on the plant.
A. The dendrobium looks like it has mite damage, not thrips, although it is hard to tell without seeing a close up of the upper and lower leaves. The new leaves look like they are being affected by mites too, so I would say the mites are still active. They seem to affect dendrobiums and thin leaved orchids much more than they do the thick leaved orchids like cattleyas. They also thrive in dry environments, so many indoor growers have to learn how to cope with them. You first have to kill the mites on this and possibly other plants. For starters, take them to the kitchen sink and spray them with a mixture of isopropyl alcohol and dish soap, lather 'em up and wash the leaves. Then get a spray bottle of isopropyl alcohol and spray the leaf surfaces top and bottom. Make it a weekly event, perhaps part of your watering routine. You might consider treating with one of the three in one insect, disease and mite control products containing the active ingredients Imidacloprid, Tau-Fluvalinate and Tebuconazole. (Feb-20)
Maxillaria tenuifolia Bulbs are Wrinkled
Q. My Maxillaria has some new growths and roots but the pseudobulbs are wrinkled, should I leave her alone or repot?
A. That looks like it would benefit from being repotted. The mix looks worn out and the pseudobulbs are probably dehydrated from the moss breaking down. You can safely repot now because new roots are forming. Keep it in a smallish pot, it will tend to grow up and out. A basket would be great.
White Spots on Leaf
Q. What is this bug and how do I get rid of it?
A. I couldn't tell what the problem was from the pic of the top of the leaf, so I asked Humberto to send a pic of the leaf underside. The scale infestation is clearly visible on the bottom of the leaf. The first step was to spray the obvious scale with alcohol and follow up with a drench of one of the Bayer Three in One products containing imidacloprid as one of the active ingredients.
Phalaenopsis Leaf Blemish
Q. I was given a Phalaenopsis in rotting, moldy bark medium. I removed all the medium, perched it on a plastic bottle I've punched full of holes, and it's been growing in 'air' for four or five months now. I spray it twice a day with spring water, and also spray with fertilised water. The roots are NOT sitting in water. It seems healthy enough -- new roots and a leaf are emerging, and the old leaves do not look like they are yellowing. That top big leaf grew while it was with me. While it was still in bark medium, one leaf developed these mark, but they have not enlarged. Should I trim the leaf?
A. Whatever you are doing, don't change a thing! Do not worry about the bottom leaf blemish, eventually your plant will shed the leaf and you won't have to look at it anymore. It looks like something happened to it when the leaf was originally forming, but there is no active infection. Good growing!