(A rather long photo-essay on dividing and repotting )


The Plant, before the operation.
The challenge of repotting an overgrown plant is one of my least favorite tasks in the greenhouse. We used to only repot in the spring because of the damage to growing roots caused by removing old medium and packing in the new.  We were concerned that we would set the plant back too much unless the summer growing season was near.  Now, however, our conversion to using Berger BM6 (see culture page) allows us to repot at any time, since there is far less root trauma than when we used bark mixes.  The following photo-essay will illustrate dividing and repotting an overgrown Cattleya jenmanii by me (John), and will also show how healthy Cattleya root systems are when grown in the medium.
The plant above was purchased in a 5-inch pot filled with BM6, with moss covering the surface, but the plant had been allowed to become very overgrown so that many very long aerial roots were growing outside the pot.  I moved it to an 8-inch pot, adding BM6 to fill in the extra space, about a year ago, but not all of the aerial roots would fit.  The plant bloomed the following spring on two leads, then again in the fall on three leads.

In late October, I noticed some new roots sprouting, and decided to tackle the chore of dividing the plant before it became even more overgrown.  Some of the aerial roots shown above were left from when I bought the plant, and I really didn't think they were alive.  The single, remaining flower spike had begun to fade.  Some action was long overdue.
The tiny new roots shown in the picture on the right told me that the situation would only continue to get worse.  I no longer want to see these before I repot. I actually prefer to repot before this stage, because these new root tips are very tender.  If I had waited any longer, however, the tangled mess of roots that I suspected would only have become more dense.  So, I gathered my tools (see below).
New roots prompting action
My simple repotting tools (no potting stick!)
My tools consisted of a torch-sterilized pruner and a new straight razor blade.  I also had on hand some ground cinnamon (which I often use to sprinkle on a newly cut surface because of its reputed antiseptic properties) and some rooting hormone, which I only use on divisions that have few or no living roots.
Next, I squeezed all around the pot to loosen the roots from the walls of the pot, turned the pot over, and popped the plant out or the pot (holding onto the plant, of course).
The unpotted plant (see below)had a root growth that filled the pot, and, unfortunately, some of the roots had begun to circle the inside of the pot.  This indicated that the project would be tougher than it would have been if I hadn't waited so long.  THERE'S NO EXCUSE!  DON'T WAIT UNTIL THE ROOTS GET THIS DENSE!
Roots filling pot, and beginning to bind together
I began by rinsing the BM6 from between the roots with a fairly strong stream of water.  This process revealed more and more live and growing roots right into the center of the root ball, and also revealed a tangled web that needed to be teased apart in order to separate the divisions without losing all of that great root growth  (see below).
Stages in rinsing away the medium (above and at right)
At his point, I turned the plant upright and decided to make my cut in a place that would divide the plant unto a large four-bulb front division that had two leads, and a back division that had seven bulbs but with many smaller and older.  The second division had only one new lead.
The cut, before (left, at place marked by pruner), and after (above,  being pulled slightly apart).
After making the cut, I contiued to rinse out the BM6 and started to unravel the roots with my fingers, taking care not to damage too many growing tips.  Because of the density of the roots, right to the center of the root ball, and my concern for doing as little damage as possible, this was a somewhat tedious procedure.
Stages in th unravelling process (above and at right)
Finally, the ball had been untangled enough to begin to seperate the two divisions.  At this point, I noticed that the only area in the root ball with dead roots was a place where the roots had been confined to a small, square pot.  This had probably happened very early in the plant's life, when is was still a seedling.
Seperation almost complete
Slowly, the two divisions begin to come apart.  And the, finally, they were completely seperated.  The two lead division (below left) had a huge number of growing roots, and the back, single lead division (below right) had less root growth.
Two lead division
One lead division
The one lead division (above right) contained the area of the root ball that had been confined to a small pot in the past and had few live roots, so I decided to cut off the back bulbs with poor roots.
Since I have a hard time throwing out any plant, I now had three divisions to pot.
Final division of back bulbs from a strong single lead division, cleaned up and ready for potting.
The only thing left is to pot the divisions.  The job is almost over, now.  I'll illustrate potting the one lead division, first.
I usually use a new plastic pot.  They're cheap, so why take The chance of transferring a disease from a former occupant to your new division?  In this case, however, I'm using the same 8-inch pot that the undivided plant was growing in.  I first put some packing peanuts in the bottom of the pot (at right) in order to minimize the loss of potting medium through the drainage holes  (right).
Next, some BM6 is placed over the peanuts, and the plant is positioned in the pot (left).  as you can see, the roots are comfortable in the 8-inch pot.
Then, I scooped in some moistened potting mix into the pot (right and below).
As a final potting step, simply water the mix into the pot and around the roots.  I don't pack the mix at all!.  BM6 is formulated for high porosity, and packing can reduce the air spaces.  Just hose the mix in, adding more mix as it settles until the level is even with the growing stem (below).
If the plant has few roots, or seems somewhat unstable, slip a stake in next to a bulb and tie up the plant.  I only do this for plants that are very short of roots.  After a few monthe, the stake can be removed, because new root growth is usually rapid.
And, finaly, just put in the label, and that's all there is to potting.  You can see that this is very gentle on the plant, particularly when compared to packing in a bark mix (with a potting stick), or even when compared to the gentle squeezing in of sphagnum.
I wanted to quickly show the potting of the two lead division, but my photo of that lead (below) was out of focus.  Nevertheless, you can tell that the roots were too prolific to fit in the 8-inch pot I had planned to use, so I had to move up to a 10-incher.  Even in a ten-inch pot, the roots are pretty crowded, and I'll have to divide and repot again at soon as each new lead develops a new bulb.
The pot is being held between my feet
The 2-lead division was potted following an identical procedure as was followed above, and the smaller back-bulb division was similarly potted in a 4 inch pot.  The small division had almost no live roots, and so the cut end of this back-bulb division was dipped in rooting hormone, and the division was staked in order to provide some stability.
The final picture (below) shows the completed group of repotted plants
Divided and potted group of three (4", 8", and 10")
And, that's all there is to it!  (It would have been even easier if I hadn't procrastinated, so repot early and often)
Watering in the mix