repotting very large root bound cymbidiums.
 

I'll try to make sense of what this describes and hope the pics do a better job of explaining. I divided and repotted two cymbidiums today that have been neglected for far too long. One was last repotted in 1995. The other at least 6 or 7 years. Most of the oldest pbulbs had died and the roots were very tangled and most dead. The media in the pot was almost non-existent and there were lots of earthworms. But both flowered every year with very nice blooms. Names of these are unknown. I've had both since I started growing orchids in the 70's. I've been dabbling in orchids for a long time. Never put much effort into them. If I found one in a trashcan or dumpster I would get it out and try to get it to bloom. No I don't dumpster dive. Usually they were left by the dumpster for anyone to take. Anyway here is my method. Well one of them at least. I have lots of different methods depending on the condition of the plants. The pics will be from the beginning to the finished pot. Hope they make sense. I don't know how to write stuff, put in some pics, and then write some more. Here goes. This is what the roots looked like when I took it out of the pot. Mostly dead. The live roots are all around the very outside of the root ball. First I clean all the old sheath material off the pbulbs. This is where I see how many new eye buds there are. Then I start to cut off the old dead mushy or hollow roots. Most of these live roots aren't necessary to the health of the plant. These are all mature pbulbs and they have all the starches, sugars, and water they can hold. The function of these older pbulbs is to supply food and water to the new growth as those new growths have no roots to absorb nutrition and water. Once I get all the roots untangled and cleaned of old root material, I prepare the pot (I take a lot of time searching through the root mass cutting out what isn't necessary and trying to get out all the old media). One of the divisions I wanted to pot into a large pot so it can stay there for a couple years and it is a prolific grower. So I put a lot of broken pottery in the bottom to take up room. I used nothing but large bark. I like large coarse potting media so I can water more often without the inner portion of the pot staying wet. That way I can also fertilize more often. When I am ready to put the potting mix in I hold the plant up at the height I want it to be when finished and pour in the mix. I tap the side of the pot all around to settle the mix around the roots. It's not necessary to get mix into every nook and cranny. Pore spaces are ok. These aren't terrestrial plants. I place the plant so as to have as much room for the new growth to grow into. Once the cym divisions are potted I put them in a cool dry place and don't water until the next day or even two days later. I want the plant to heal all the damage I've inflicted upon it so there is less chance of getting any fungus/bacteria into it's system. So..,. I hope this stimulates questions and comments. I've used these methods for years and have lost few cyms. They push lots of new growth and flower next season. Here's the pics.

Here are a few things I want to show the new growers here. Old sheath material is a great place for bugs and other dastardly things to lurk. The dark alleys of orchid growing. When you repot, clean it off. Just pull it off when it is dry and crispy. Roots.....you don't need them all. Here is what a root looks like. Hard wiry thin root inside a spongy material called velamin. This material absorbs water/nutrients quickly for the root to absorb over time. New eye buds....this is what they look like before you see them growing as new pbulbs. I use the squeeze between the finger tips test when deciding whether to cut a root. This is true for any orchid root I'm going to cut. Squeeze it. If it is hollow or soggy, cut it. If it is firm, no matter how brown or gray it is, don't cut it. Of course I cut lots of live roots on this one because it didn't need all that root mass. Bug poop. Mostly earth worm castings. Good stuff for most plants but not for orchids. Cyms can take some soil but other orchids can't. Damage from salts in the water on cym leaves. This is how my water here affects cym leaves. New growth. Love it. Take care not to damage these new shoots if at all possible. The old pbulbs and leaves are not what's important. These new growth buds and shoots are your flowers in the future. Most cyms are two season plants. They push out new shoots the first season. These mature in season one. Then the next season they flower. Any damage to the new growth will most likely damage your future flower production. Cyms are hearty. Very tough plants but there are some things to watch out for. Damage to the plant and too much water. They like to eat. Feed them. Weakly weekly. Potting. Don't bury them. Let them see light. And....you don't have to fill the pot. You can use a larger pot if you just don't put so much potting mix into it. Look at how much rim there is in the pics here.

Back bulbs. Here is what they should look like when they are cleaned. Just put them in a pot without media and put them in a cool dry place. They will most likely push dormant eye buds in a couple months. I hope this all makes sense and you feel you can repot a root bound orchid now. It's easier than it looks. Oh, and here are the pics of salt damage on cym leaves from too muc food or salts in the water. Sorry, I guess I don't have the pics of salt damage.

Nice explanations, James!

Some really great info here - I don't grow cymbidiums (erm, yet?) but seeing all this step by step with so many pictures is awesome. Also good to know about keeping those backbulbs - would this work for other orchids that have p-bulbs as well?

No. Bbulbs from most other orchids do not resprout after they give up their energy to the newer growths. As long as they are still attached they can push dormant buds though.

James you should do a web series lol
Very good and informative season

Thanks flex

Thank you for some great photos and information. I have several Cymbidiums and two in particular are really pot bound to the point where new p-bulbs are forming over the edge of the pots! This has inspired me to make a good effort and repot them.

I think the key to success is to take your time and don't try to keep everything. The back bulbs aren't necessary to the health and vigor of the plant. I keep no more then 3 to 5 even when I repot every other year and the roots are good. I propogate the BB's to get more plants which are given away.