If you want to make an orchid lover cry, say the words “crown rot” out loud. This phrase instantly conjures up images of collapsed plants, rotten stems, and dead leaves.
On top of potentially being fatal, once a plant is infected it can go from seemingly healthy to dead in a matter of days.
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Crown rot is all too common and it seems like most orchid growers encounter it at one point or another.
Don’t panic. It can usually be prevented or, if not, treated if you catch it quickly.
You just need to know what to watch for in your orchids and if you notice signs of infection, take action quickly – and this guide will help you do that.
Here’s what we’ll go over to help make that happen.
What Causes Crown Rot?
Crown rot is a catch-all term for when the aboveground parts of a plant start to rot. In the case of orchids, this might include aerial roots, stems, and leaves.
In many plants it begins at the base of the plant – the crown – where the stems and leaves meet the roots at the soil level. Crown rot is a common problem in landscape trees.
The disease can be caused by bacterial or fungal pathogens including Citrobacter spp., Dickeya spp., Enterobacter spp., Fusarium spp., Klebsiella spp., Pectobacterium spp., Phytophthora cinnamomi, P. nicotianae var. parasitica, P. palmivora, Providencia spp., Pseudomonas spp., Serratia spp., and potentially others.
Or, it might simply be caused by water being in constant contact with an area on the plant.
That’s why it’s extremely common in species where the leaves wrap around the stems, as they do in the case of Phalaenopsis aka moth orchids.
There isn’t much room for the water to drain out of tight areas like this, so it tends to pool and become trapped.
This wrapping, scale-like stack of leaves on the stem is an adaptation that allows for orchids in the wild to capture the water and nutrients from the air. But in your house, where you’re providing plenty of moisture, there can be too much of a good thing.
Any orchid species is susceptible, though, regardless of the leaf structure.
Identification
Symptoms of crown rot start as yellow, brown, or water-soaked spots on the stems or leaves.
That may sound easy to see, but the rot can develop in hidden areas like in the sheathing, sheathing bracts, or parts of the stem underneath the leaves. Usually, the lower leaves are impacted first.
More subtly, impacted orchids might not develop new leaves. Since some orchids, like Phalaenopsis, develop leaves slowly, you might not realize this is happening until it’s too late.
You might also notice a foul smell. You might have to get in close to experience it, but it’s there. That’s the plant tissue rotting.
You could also see the velamen – the silvery coating – of the aerial roots turn bright green and even start to develop rotting spots. The velamen tends to be more green in color when the soil is moist and more silvery when it is dry.
The base of the orchid might turn dark brown or black, and mushy or water-soaked.
Eventually, the entire top part of the orchid will die, with the leaves turning yellow and brown, wilting, and eventually collapsing. Take a close look at the plant and you’ll probably find that the damage starts right at the base, and the roots may be unaffected.
Or in some cases, the base might rot through completely and the top, healthy part of the plant will simply fall off, like someone took a knife and sliced it clean away. When this happens, it’s generally referred to as collar or stem rot.
Rot that is caused by bacteria tends to be much quicker-moving than the other causes. A plant can be killed in just a few days if bacteria is the causal pathogen. In general, once infection takes hold, crown rot can move fast, so act as soon as you see it!
Organic Control Methods
You’ve heard it before and you’ll hear it again: Prevention is best.
In this case, prevention involves watering at the soil level and not on the foliage. Better yet, this is your chance to practice bottom watering instead of soaking your plants from above.
If you’ve never tried bottom watering before, it’s easy. You place the orchid in a dish or sink filled with a few inches of water and you let the plant absorb all the moisture it wants for 15 minutes or so.
Then, you remove the pot and let it drain for about half an hour. Learn more about bottom watering in our guide.
Mounted plants are far less susceptible to rot, so consider mounting your orchid if you struggle with diseases regularly.
Learn more about proper orchid cultivation in our comprehensive guide.
As soon as you notice something is wrong, remove any symptomatic areas, if possible, using a sterile knife, scalpel, craft knife, or pruners. Be sure to cut a clean margin around the diseased tissue so that all diseased tissue is removed from the plant.
If the damage is throughout the entire base of the stem, you obviously can’t cut that out, so at that point it’s time to break out the organic and chemical fungicides.
Be aware, though, that if the disease has progressed significantly you’re probably fighting a losing battle. If this is a precious orchid, you can try to propagate it via seeds or cuttings to replace it, if possible.
Once you’ve cut out any rot, repot the plant in fresh potting medium into a clean container.
Learn more about how to repot orchids in our guide. And make sure you choose the right type of container for the species you are growing!
Organic Fungicides
Fungicides are useful if you catch the issue early. Once the rot is extensive, fungicide applications can help, but you’ll still need to prune out the damaged tissue.
You’ll often hear people suggest using cinnamon to treat fungal issues, particularly on orchids.
I don’t know how this trend started, but it’s certainly not a method to try in this case. The kind of dried cinnamon that we keep in our spice cabinets has lost the effective compounds that help treat fungal issues.
It can help by drying out material, but otherwise, it isn’t going to be effective enough to tackle a serious problem like crown rot.
You need something a bit stronger.
Copper fungicide is a reliable option that works on many different fungal problems, but it needs to be used carefully. Don’t use it on any plant that isn’t currently in bloom or on any Dendrobium species.
Spray the plant and the soil once every two weeks using a product like Bonide’s liquid copper fungicide.
Bonide Copper Fungicide
Grab a 32-ounce ready-to-use or 16-ounce concentrate at Arbico Organics.
Mycostop is a gentle biofungicide that harnesses the power of the beneficial bacteria Streptomyces Strain K61. Spray it every week until symptoms resolve.
Mycostop Biofungicide
Arbico Organics also carries this product in five- and 25-gram packs.
A fungicide that contains citric acid may also be effective.
Procidic
Once again, Arbico Organics carries Procidic, a broad spectrum, citric-acid based fungicide, in 32-ounce ready-to-use, 16-ounce concentrate, or gallon concentrate sizes.
Chemical Fungicides
You probably won’t need to use chemical fungicides since the organic products work well, but they are always available if you want to try them.
Which products to use will depend entirely on the type of orchid you are growing. Be sure to follow the manufacturer’s directions to the letter.
Chemical fungicides can be dangerous both to plants and to human or pet health, so you must exercise caution when applying.
Rot Be Gone!
It’s truly horrifying losing an orchid to crown rot. It seems to sneak up suddenly and turn your previously happy plant into a floppy, miserable mess.
You can usually prevent the disease by watering at the root level and not on the leaves, but sometimes those pathogens just can’t be stopped. As long as you catch it early, you can potentially save your plant.
What kind of orchid are you growing and what symptoms are you seeing? Let us know in the comments section below.
And for more information about growing orchids, you’re sure to enjoy these guides next:
