Paph newbie help! Is it rotting?

[Kim in CT]

I purchased my first paph in March and repotted to S/H in April (Paphiopedilum philipinense x (roths. 'Jungle Selected' x roths. 'Atlantis' SM/TPS). It has lost one of its lower leaves and looks to be losing another. Is it sick? or is this a normal transition thing? It's been growing inside, bright indirect light, ~50% humidity and 60-70 degrees F and I'm getting ready to transition all of my orchids to grow outside for the summer. What should I do to help my paph survive? Is it rotting? I'm hesitant to disturb it until I hear from more experienced growers. Advice please?

[estación seca]

It's losing a lower leaf. This is how they fall off normally. But the question is - why is it happening? That plant should be able to support that leaf.

How do you water it? How often? Do you keep the reservoir always full?

In general it's better not to transition to S/H until a plant is actively growing roots. Paphs can grow roots at any time of the year, but 60-70 F / 15.5-21C is very cool for this kind of Paph. They will tolerate this kind of temperature all winter, but won't grow much. I would not have moved that plant to S/H when temperatures were in that range.

[Kim in CT]

The reservoir has been topped off ~twice a week with KelpMax + dilute nutrient solution, and it has been flushed with tap water (TDS 80) once so far.

Since it's already in S/H, what might be suggestions for moving forward from here? Thank you for the help!

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At every watering with S/H you should fill the whole container to the brim with watering solution, then let drain. That's called flushing. Don't add just a little bit of water here and there. The concept of "topping off" isn't part of S/H culture. The reservoir should never go dry, and the LECA should remain moist.

I suspect your plant needs more water. If you do a thorough watering 2-3 times a week it will probably be enough. The more frequently you water plants in S/H the faster they grow, if conditions are otherwise correct.

KelpMax should be used no more than once a month during active growth. But that isn't what's causing the leaf loss.

Your tap water is fine for this plant. No need to use reverse osmosis water, nor distilled. When you say "dilute solution of fertilizer", what do you mean? Which fertilizer are you using, and how are you diluting it?

And back to the temperatures - Paph. rothschildianum in habitat experiences night temperatures like yours, and lower. But, the days are warmer. If there is any way you can keep it warmer during the day in the winter, it will be a lot happier.

[Kim in CT]

The "dilute solution of fertilizer" is distilled water + calcium nitrate (30 ppm) + magnesium sulfate (20 ppm) + Jack's hydroponic Part A (100 ppm) + KelpMax (20 ppm). I've been keeping the reservoir filled with this via topping off after a 15 min soak in the same solution ~weekly. Soak = I cover the holes in the container with tape and fill with the solution, wait, then remove the tape and let the container drain.

Would a seedling heat mat be ok to increase the temp for the paph (heat from the bottom only) or does the entire plant need to be kept in a warmer room?

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The Jack's A has enough magnesium, so you don't need to add the mag sulfate. I would definitely use your tap water rather than spending the money on distilled; your tap water is fine for multifloral Paphs. In fact, some of those dissolved minerals are likely calcium. I use tap water with more than ten times your total dissolved solids, and my Paphs grow fine. As mentioned, use KelpMax no more than once a month.

The orchid curator at the Huntington Botanical Gardens uses only calcium nitrite plus high-mineral well water for all the slipper orchids.

Pardon me for misunderstanding, but I'm still a little unclear on what you're doing.... How deep is the reservoir in your container? After a soak and drain, are you allowing the reservoir to go dry before refilling it? Do you then add just enough solution to fill the reservoir to the level of the holes, or do you again fill the whole container and let it drain?

The idea of S/H is to have a constant reservoir and constantly moist LECA in the pot, combined with frequent watering by filling the container to exchange all the air in the pot. The roots that grow are adapted for this environment, and not to a standard wet-dry potting environment.

It's important with S/H to fill the entire container at each watering, frequently, to displace all the air, and entrain fresh air as the solution drains. Adding a little bit of solution to refill only the reservoir will lead to salt buildup in the medium, which can also cause damage to old leaves - which is the problem you originally posted.

And if the reservoir regularly goes dry, or nearly dry, it isn't S/H culture - the roots never adapt to being continually moist, and most of the benefits of S/H are lost. It then becomes standard culture with LECA. One good watering a week for a multfloral Paph in LECA isn't enough.

I suggest not doing 15-minute soaks. They're unnecessary with S/H. Every time you water, pick up the plant. Take it to a sink, or hold it over a bucket. Cover the holes with your thumb, or the heel of your hand. Fill the container to the brim. Let it drain immediately. There is no reason to leave the plant soaking in the solution.

Do that at least twice a week; three or four times would be even better. If you notice the reservoir going dry you should do this more often. You don't need to water until the reservoir is almost dry, but orchids in S/H grow better and faster the more frequently they're watered.

Setting the plant on a heat mat is usually enough. Every room is different, of course. I might suggest putting a similar pot with moist LECA but no plant on the heat mat, and measuring the temperature of the medium near the bottom of the pot after a few hours. Heat mats can overheat and damage roots.

[Kim in CT]

ES, Thank you SO much for the detailed information. I was doing S/H all wrong ...

My reservoirs are ~1.5 inches deep, and I would top it off during the week with the nutrient solution when the level was maybe half-way between the drainage holes and the bottom of the pot. They never went totally dry. Then on weekends I would do the soak and drain. The LECA on the top would look pretty dry during the week but I could see the humidity mid-pot.

I'm excited to change up my method and I hope it's not too late for my paph.

Does the same general advice hold for my fledgling cats and dendrobiums? Especially regarding my tap water and the nutrient mix you recommended in your replies?

Thank you again!

[estación seca]

Your Paph is still in good shape.

Brandon Tam at the Huntington gives the slipper genera 10 parts per million of nitrogen at every watering. That is a lot less than most people give other genera. You can read lecture notes of his talk if you use the Search feature in the maroon menu above; click Advanced, then search term DVOS and my partial username estaci .

I read about S/H and about fertilizing in great detail on the First Rays Web site, run by OB member Ray. I strongly recommend people who want to grow in S/H to go there. It's also the place to learn about fertilizing.

In my opinion Catts and Dens do better with more nitrogen than Paphs prefer. Not much fertilizer is needed during cool weather, and most Dens are better with no fall-winter fertilizer. But the warmer the summer, the more nitrogen they can use. Ray suggests using 25-75 parts per million nitrogen with every watering. In my very warm sunroom I've found they grow faster with even more summer nitrogen.