Let's begin one step at a time. When do I divide and
repot my orchid? That simple question has two parts.
There are signs that indicate the need for repotting and/or dividing your orchid. One year your cattleya produced 20 magnificent 6-inch blooms. The next year it produced only 6 blooms that measured 4 inches across on only one side of the plant. Another sign is that the newest growth is smaller than the last growth. Each new growth should mature taller and stronger than the previous growth. These are the two most dependable guides.
Would it be best for the orchid if I just repotted it into new mix or would it be best if I divided it and repotted the divisions? This all depends on how large the orchid. If the orchid is outgrowing a four-inch pot, repotting is most likely the solution. If the root mass is cracking an eight-inch clay pot (you are an excellent grower!), dividing and repotting this magnificent specimen would be the best choice.
Another important consideration is the condition of the orchid. If the orchid is starting to deteriorate with lots of old shriveled back bulbs or if the center of the plant is dying off as the outer parts continue to thrive, then it would be best to divide the orchid, discarding the dying parts.
If you have decided that your orchid in a four-inch pot has outgrown its container, repot it after it has bloomed. Clean off the old medium entirely and simply step it up to a new six-inch pot with new potting medium.
Now you have grown this orchid into a specimen that even impresses you! The plant is in great condition, but it's just too big or has moved past it's prime. Now it is time to consider dividing and repotting. Bookmark this: The orchid is a lady. Timing is everything! The orchid will decide when to divide and later when to repot. You are no longer in control. She will direct you. Once you accept this, you and your orchids will bond.
Divide only when your orchid is putting out new leads. By dividing when she is in this stage of growth, more new growth will be activated. To divide, select the place or places to cut the orchid. Cut through the rhizome with a sharp, sterile instrument. Sprinkle a little cinnamon on the newly cut rhizome and mark the division with a clean label or a piece of bark. These markers will make it obvious where the surgery was done. This completes the dividing segment. Set the plant back on the bench and water and fertilize her as usual. Wait for her signal to repot. Be patient. Repotting is next, but it may be several months before it's time.
Timing is everything. You're doing what is best for the orchid. She will reward you. Watch for new roots. The time to repot is when your orchid is establishing new roots. Allow the roots to grow to two to three inches before repotting. Remove the plant from the pot, wash off all old medium, and gently separate all the divisions you have created. Now you may repot all of the new divisions.
This two step procedure will reward you with stronger divisions that will bloom sooner than if divided and repotted at your convenience. You have lessened the stress of major surgery. Most of these divisions will bloom during their next bloom cycle. That's the reward! Finally, if your orchid has gone way, way past it's prime, it might be best for the orchid to just be repotted. Then let it gain strength before dividing. Growing orchids is fun and rewarding. Dividing and repotting your orchids is part of the fun. All you have to do is let your plants tell you what they want - just like any lady. And if you do what she wants, she'll reward you with lots of wonderful blooms! Happy growing.'