How to divide Cypripediums


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Abgeschickt von Michael Weinert am 13 Oktober, 2007 um 09:41:59

Dear fellow Cypripedium growers,

I have learned that many of you are quite reluctant when it comes to dividing a well growing, big Cypripedium clump. It is a pity as we lose many good clones, because the plants will die anyhow, may it take 10-15 years (like a Cyp. 'Gisela' at my parents) or 25 years (like a huge Cyp. calceolus clump in another grower's garden). The reason is that with the time the vitality of the plant goes down, the old parts make a bigger and bigger part of the rhizome and the roots and one day a fungus spreads over the whole clump, killing it within a few months. Then it is too late to do anything against it. See the photos how a multiple shooted plant looks like. You can imagine that when it becomes even more dense over the years and the percentage of dead roots increases, a catastrophe is preprogrammed.

Here is an example, a Cypripedium 'Emil' with 72 shoots (which takes less than ten years, by the way). Left the clump from above, right a division from below.

  

And if you look closely, you see exactly what I mean. The old parts start to die and will eventually kill the whole clump within one season when the state of decay gets out of hand. It is just a matter of time.

This is the reason why a clump bigger than 10 shoots has to be divided in order to keep the risk of a total loss low! I only let clumps grow bigger than this if I have enough divisions elsewhere in a vital state. The widespread hesitation to divide a big clump comes from the experience made with plants which have already grown too big, 20 or more shoots, grown at the same place for 10 or more years. These plants have less vitality (the growth rate declines with the number of shoots, the percentage of old and non-vital tissue increases) and therefore have an increased risk for infection and rot. Furthermore it is nearly impossible with such big clumps to divide them without serious injuries to the plant tissue. However it is not impossible and should nevertheless be made because otherwise the lifespan of this particular clone is anyhow limited. I divide my plants every few years and in this way their vitality remains high. I haven't lost a single clone to dividing (and I have divided many plants as you can image when one runs a Cypripedium nursery), on the contrary, several clones would not have survived until today if there hadn't been a few seperate clumps of the same plant in my collection. This is my motivation to show you how I do it and how you can also do it successfully. As an example I show you the dividing of an Cyp. 'Emil' clump with approx. 30 shoots (I repeat that it is not normal for me to let Cyps grow so big).

The best time for dividing is autumn (September, October), shortly after the shoots have died back. 

Step 1: Get the clump out of the ground and remove most of the soil by using cold tap water.


Step 2:
Remove all dead shoots. The easiest way is to pull sideways, not upright! Don't cut the shoots off, the remaining tissue may rot and cause problems. Don't worry that you injure the rhizome. 
The only exceptions are Cyp. flavum, Cyp. reginae and their hybrids (e.g. 'Ulla Silkens'). The shoots of these plants don't seperate well from the rhizome. Cut them off, don't try to pull!

 


The photo below shows the clump after removing the dead shoots. As you can see the shoots have perfectly separated from the rhizome. All have been pulled off, not cut!


Step 3:
Now clean the clump thoroughly with cold tap water. Use a strong flow of water to ensure the complete removal of all soil, especially on the underside of the rhizome. 
This keeps the risk of rot low and makes it easier to divide the rhizome.

    


Step 4:
Now bend the clump up and down to loosen the net of roots and find a spot in the middle where the rhizome breaks apart (you will hear and feel it). This procedure can require quite an amount of strenght, but don't worry, it won't harm the plant. Only use a knife if the clump is so dense that it is no longer flexible. And this were already the state where I would say that you have waited to long for dividing. A knife injures a lot of plant tissue and cuts roots, therefore avoid it if you can.

  


Step 5:
Now you can pull the two parts apart. Don't just pull straight, move both hands in various twists and angles so that the roots of the two divisions can separate from each other without breaking. 
This is the point where the thorough cleaning of the clump (see above) helps a lot.

  


In this way you can divide the clump step by step (the photo below shows the dividing of the bigger part in the photo above right).

Step 6: Remove all broken and dead Cypripedium roots, roots of other plants and any other debris. In this way no rot occurs after replanting. There is no need for fungicides, activated charcoal or anything like this! Even if the plant is in a bad state, only good culture conditions help the plant to recover, according to my experience. The use of chemicals has never produced convincing results for me.

   


Now we have three big parts which are still too big in my eyes (except you want them for a show or an impressive garden display). 
If you want to keep the plant in a vigorous growth state (and so having the lowest risk of loss), you should divide it into smaller pieces. This applies especially for rare species or special clones where you have only a single specimen in your collection, not so much for the everyday plants! The reason that I am showing here an 'Emil' is not that I would not do such a procedure with a Cyp.debile also. It is just that this clump was right at hand and is a good example how even a huge clump can be divided into many pieces.


So we repeat step 4 to 6 as often as needed.

   

   


The three divisions on the right side have reached their minimum size for a secure and fast growing on. Don't think that they now would need time to recover. These plants will flower and grow on as normal, but multiply by far faster than before! If you wanted you could do this procedure with the clumps on the left as well.


This is all what has been left as debris from the dividing of the whole clump as shown above!


Step 7: Rinse all parts again thoroughly with cold tap water. 


Now they are ready for replanting (if you don't prefer to divide the clumps on the left into smaller pieces). 

I hope that this instruction has given you a good insight how I work with all of my plants every few years. Experience convinces me that this is the right way to insure the existence of Cypripediums in a collection (be it garden or pot culture) for a long time. Not dividing is never the solution because the lifespan of an untouched clump is limited! You may know enough examples of this fact from your own plants or from the moaning of fellow growers.


Happy growing

Michael


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