Every now and then, we take a walk through the Orchid Wise Shade House to check what’s flowering or to spot anything interesting. The shade house overflows with all sorts of orchids—species, primary hybrids, modern show bench hybrids, and everything in between. You never know what you’ll find! This time, we’re diving into our second article on Cymbidium bulb rot.
In our previous article on Cymbidium Bulb Rot we explored one of the causes of bulb rot – too much water, and included photos of what a rotting bulb looks like. This time we take a closer look.
While inspecting the Orchid Wise Shade House this week, I found a species Cymbidium looking a bit poorly. A quick visual check confirmed the early stages of bulb rot. And I was a little bit beside myself….
This plant held significant value in my collection as a breeding specimen, so you can imagine my devastation when I realised how bad it looked. The plant is an exceptional specimen of Cym. hookerianum and very much worth saving. An image of it in flower in 2024 is here.
My experience with Cym. hookerianum is that it is quite prone to rot in my environment. All but one of my Cym. hookerianum’s this year have suffered from some sort of rot….having not been repotted for a number of years.
People often over water their plants at this time of year (Summer). It’s a myth that Cymbidium orchids need to be watered every day in Summer. Every 4 days seems to be a good balance, but often on the hotter days your plants will benefit from a light misting, just to increase the humidity.
Anyway, back to the issue at hand…
The bulb was a bit squishy when squeezed, a clear sign of trouble….
After removing the pot, I discovered a buildup of broken-down fine material, which left little to no air space for the roots. The roots had turned mushy and brown, and despite going days without water during a scorching week, the root ball remained wet. No surprise the bulb had started rotting—too much water was the undeniable culprit.
I squeezed the other bulbs on the plant, and none felt soft. Everything seemed fine at first. But here’s a common trap for beginners, and experienced growers alike —the plant was beyond saving, and I’ll explain why.
Cymbidium orchid bulbs are connected by a rhizome. It’s the part you need to sever when dividing your plants. This rhizome carries and transfers nutrients and water between bulbs. But it also transfers any nasties in a bulb to other bulbs, like virus, and in this case, rot.
After removing the pot, I stripped the roots and severed the rhizome connecting two bulbs—confirming my worst fears. Above are the photos of two of the bulbs I cut apart.
It’s a little hard to see in the above photos, but almost the entire diameter of the rhizome is black.
The next photo provides a close-up of the rhizome between these bulbs. A black rhizome is neither normal nor healthy—it indicates that the rot has already spread from the soft, squishy bulb into the next, seemingly healthy bulb. At this stage, saving these two bulbs is impossible. It’s only a matter of time before the next bulb softens and dies as well.
Thankfully, there were positives for my situation!
The good news? I managed to save a clean back bulb from the plant, which I’m hoping to strike.
Another positive was a decent-sized lead on the other side of the plant. This lead remained clean, showing no signs of rot. We’ve since used it to clone the plant. A good number of eyes were extracted from the lead, and with some luck, we’ll soon have clone tissue to work with.
Make no mistake though. By the time you find rot in a bulb, it’s probably too late for the bulb, and potentially, other bulbs connected to it. Any part of the rhizome that is black will be contaminated by rot, and once infected, it is almost impossible to save the bulb.
So please check the roots of your plants fairly regularly to ensure they are healthy. Re-pot to ensure the best environment for you roots. Maintain a good watering regime and inspect your plants regularly so you can spot any issues quickly. You won’t regret it!
