The Coryopedilum Chronicles IV - Potting and Watering

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May 14, 2017
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Dallas, TX
The Coryopedilum Chronicles IV – Potting and Watering

This Chronicle documents the process of potting deflasked Paphiopedilums as well as the watering approach I use to make this task as efficient and clean as possible in a home environment when dealing with a large number of plants.


When making compots, it is important to have a systematic approach to grading the plants, or clumps of plants. I have always made these decisions based on the root systems as the depth of the roots of a given plant has the greatest impact on the ideal watering schedule. The mix in the upper portion of a pot dries out far more quickly than the center, or even an inch down, and so seedlings that have only put out a small root or two are going to need more frequent watering- and certainly in the first couple of weeks as the potting mix increases its capacity to retain water (soaking the bark a couple of days prior to potting helps- but there is still improved absorption to come after the potting mix is used.)

The ultimate composition of a compot is going to vary widely depending on the individual seedlings, but in case it is helpful to you starting out, I can offer the following averages I have encountered over time. For a Paph flask that yields 25+ viable seedlings (meaning with 2 or more leaves each and at least one good root), a good rule of thumb is that you will get 3 compots if you are using 4 inch pots. One pot will contain the 5-7 seedlings with the largest root systems, and the rest will have about 10 each, with any sprouted protocorms or very tiny seedlings going into enclosed growing containers.

With all compots, the base is a small number of plastic peanuts (5-6 or so) in the bottom with care taken to ensure at least half the drainage holes in the pot are not blocked.

For larger-rooted seedlings, I like to fill the pot to within about 1/3 of the top as a starting point- or perhaps less if the plants have a lot of post-flask roots. Then stand one plant on top of the mix in a corner of the pot with the base of the plant just below the top of the pot, and gently add a little mix around it- just enough to stabilize it. Continue in this manner until you have all the seedlings places, and then fill in with mix until it is level with the base of each seedling.

Here is a photo of adductum v. anitum in process to show you how this looks,

Same approach works when dealing with clumps of seedlings that are not easily separated as with these rothschildianums,

For smaller-rooted seedlings, I prefer to fill the pot with all of the mix and then very gently (using the wire tool shown in prior Chronicles or some other light implement that is not going to tend to pack the mix tightly) dig a small hole, insert the seedling and then add back mix to cover to the base of the plant.

Here is a shot of randsii potted with this approach,

Enclosed containers for sprouted protocorms and tiny seedlings

Most flasks are going to have some very tiny seedlings, or even sprouted and unrooted protocorms, which have a low chance of survival if potted up in regular compots and left to fend for themselves. It is not always worth the effort to try and save everyone, but given what good Paph flasks cost- as well as our implied duty to make every effort with species that are rare in cultivation- it is worth the time to do what you can, in addition to being a great learning experience.

My history with enclosed containers to handle tiny seedlings has not been good. Looking back, I was too worried about trying to preserve flask conditions to an excessive degree. In early experiments, I would use a combination of sealable clear food containers and plastic baggies to completely enclose the plants with no circulation to preserve humidity. Rot set in within days. Most recently (about 9 years ago), I was putting such plants in clear food containers that had potting mix on the bottom and a layer of pure Pro-Mix about a half inch deep on top. Then I would leave the lights lightly cracked open. The rot took a little longer to set it, but on it came within a couple of weeks and everything died.

This time I have taken a new approach and, to give a sneak peek at Chronicles V to come in about a week, I am happy to report a very good success rate in the first couple of weeks out of flask.

The starting point is semi-transparent sealable food containers. First, I cut 2-3 holes in the bottom of each as shown here,

Next, without a layer of plastic peanuts in the bottom, I half-filled each container with the exact same potting mix I used on the compots.

Then, I cut a large flap in the center of each lid as follows,

Once potting was complete, I put these with the rest of the plants- the semi-transparency of the lids reduces the light exposure some. And very importantly, the lids were put on loosely with the open flaps facing in the direction of the air circulation source (aka “the fan”.)

More on this in Chronicles V, but here is a quick shot of the adductum v. anitum after two weeks. All of them have survived and are really starting to look great (the flasklings were all a little yellowish and pale right out of flask), so I am hopeful that I have finally figured this out.


It may seem silly to have a detailed write-up on watering, but I have found when growing large numbers of orchids indoors, watering needs special consideration on many fronts. When watering a large number of plants in your home on a regular basis there is not just the consideration of an efficient process from a time perspective, but also sourcing and using RO water (essential for sensitive Paphs IMHO), electrical safety, plumbing, and even household pests.

My own approach has been to keep and water the plants in paired trays. And the nice thing about standard seedling trays is that you can reliably fill them with various configurations of standard sized pots, plus four seedling trays perfectly fill out one shelf in a Container Store Metro Shelving unit (the best choice for DIY home orchid growing shelves.)

The purpose of using trays in pairs is to prevent any risk of water dripping on light fixtures on lower shelves, or on to your floor.

In the past, I would cut out one corner of the inner tray so that as I watered the plants over the sink, all of the water would drain out. And then once the watering was done, I would put the inner tray back in the outer tray which had no holes (trays are of same size and stackable), and set it back in the growing area.

This worked out nicely for the most part, however additional quantities of water seep out of pots for quite a while after the watering is done, and I found over time that some of that water would seep into the outer tray where a significant slimy mold would grow between the two trays- a mold that provided the perfect feeding ground for gnats.

Not this time! One of my best improvements for these Chronicles is that I have now placed that drainage hole about a quarter inch above the bottom of the inner tray as shown here,

Once I am done watering, I drain off virtually all of the water through this hole, and then only a bit is left in the inner tray. Most of that evaporates- and so far in these new Chronicles I have not seen any notable slimy mold growth plus there have been zero gnat outbreaks.

Another key consideration is your plumbing- especially if you live in a high-rise like me and share your plumbing with 100s of other people.

This is where the strainer you saw in earlier Chronicles comes in handy once again. Once I am done watering a tray of plants, I tilt it over the strainer as I pour excess water into the sink. Then just empty the strainer into the trash and you are done.

Final note on watering- the concept of recycling. I have seen strong opinions against the practice, but I have not witnessed any long term troubles- and so yes I recycle my RO water during each watering session.

One thing I should note if you do this- before watering a tray of plays, dump out any excess drainage that has accumulated since the prior watering, and every couple of months remove the pots from the tray and wipe it down to get rid of any of that slimy growth discussed above.

When watering, just place a bowl under the strainer in the sink, and reuse the water for the next tray- adding a bit of new water as needed to finish out the process.

I buy my RO water in gallon jugs- it is expensive and involves a lot of hauling. By recycling water, I am able to do an entire watering of what is currently 4 trays of plants- or around 48 compots- using about three-fourths of a gallon. Note- I do not save water to use for the next watering day- I only recycle in real-time, as were.

This concludes Chronicles IV. Chronicles V will be coming in a couple of weeks and in them I will present a 30 day progress report with photos for each species- including a look at the early results of potting with and without flask agar intact.
May 14, 2017
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Dallas, TX
I just used a very sharp knife to cut it out- actually a Wusthof tomato knife that was once used for a non-food purpose and became permanently commissioned for non-food cutting duty.

These are standard seedling trays- so not terribly thick. I think just about any well sharpened kitchen knife would do the trick.

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