How to Repot a Dendrobium Orchid
I bought a large hard caned dendrobium with 4 developing flower spikes that needs repotting. I took a few pictures as I went along to show how to repot a this dendrobium. Before I get started I soak the plants roots in a bucket of water with physan 20 for about 20 minutes. For a smaller plant you may only need to soak for 10 minutes. Afterwards I set the plant aside while I prepare my area.
As I like to sit down while I work...I sat up a table and covered it with paper. It's alot neater to do this outside, but as we are having storms I am working inside this time. (I'll be vacuuming afterwards...) I have a small pair of scissors for fine work, a set of long tweezers, and a couple pairs of scissors to cut larger stuff off. Before working with these tools everything should be disinfected thoroughly by soaking for 10 minutes in physan 20 or disinfectant. Skipping the disinfecting step will spread disease from one plant to another.
After checking the situation, i'm relieved to be repotting. This plant was in a 3 inch pot. It had so filled it's space the pot had to be cut off. Consequently; the small pieces of wood used originally were going to be very difficult to remove. I let the water soak good and through; another 20-25 minutes after soaking I just let the plant sit.
This small amount of dirt was 2 hours of picking with the tweezers and scissors. Begin trimming roots that are rotted and squishy. They often are brown and when you pull at the outer cover it slides off leaving a thread looking thing. Be careful to leave the healthy white roots and try not to break them as much as possible. Breaks allow bacteria and fungus to attack your healthy plant. Using the tweezers, place them squeezed together in the middle of stuck together roots, they open roots and unstick them gently. Pulling roots gently apart shows where they come from. At this point though, go slowly and gently.
After 4 hours alot of the roots began to loosen and there were obvious area of progress. Unbraiding roots often must wait until the potting material has begun to be removed. The roots often attach themselves to the potting materials, sometimes even growing through styrofoam, cocoanut husk pieces, even wood. When roots are attached to a clay pot, it's best to break the pot and leave attached pieces. The pieces must fit in the new pot so try to keep them as small as possible.
After 6 hours the root ball looked good enough to wash off and sit in the corner outside. The break is necessary because 6 hours of unbraiding roots can leave you stiff and with a sore back. lol Besides, this way you let the roots dry and identify any that still look too dark to leave on. Never leave anything black on a plant you are repotting. When done spray thoroughly with a mixture of bug killer and physan 20. That way as the roots dry; pests and fungus are killed.
The plant is overnighted on the porch. But at this point, you are asking about the 4 developing spikes. To even my suprise, after about 12 hours of rest those flower spikes were doing just fine. Some of the flower buds are dripping orchid honey and developing to the point that they have now moved away from the stalk. I went ahead and potted it up this afternoon in a nice clay pot. I used fresh fir bark, a little larger grade than what it had last time. Because it is so tall I also put stakes around the edges and twist-tied a few of the p-bulbs to them to help the tall boy stand up.
Clay pot and fir bark....
Below is the finished project.
There are three main items used in a humid place (like Florida) to pot hard caned dendrobiums. There is the clay pot, a plastic pot and the wood basket. The first two are the normal, but if you have a heavy hand when watering and it seems you are killing your dendrobiums roots, try a wood basket. Place some cocoanut fiber as a liner; others also have used shadecloth cut to fit for this. Whatever is used it must be longlasting. To fill the regular pot, use fir bark or a pre-mixed orchid mix available at many hardware stores. Pots should have ample holes to allow the roots good air movement and drainage.
While this all seems quite a chore at first, as you get a few potting jobs done you'll realize it's not too bad. There are little tricks, like spinning the plant as you put it in it's new pot to get those gangly unruly roots to tuck neatly in place. Another...pot clips are great, but when those aren't around twist ties and stakes help the plant stand up until it's roots grab ahold. Then you can remove the stakes until it blooms for you.
Good luck and happy potting....
PS - Learn more about orchid repotting in the OrchidTalk Orchid Forums