Scared to repot tiny new orchids

[Rross]

Yesterday I bought 2 cattleyas (George King Serendipity and (Amy WakasugiYamanashi) and one dendrobium (Hiroshi Blue) sold in polypacks from a big hardware store. They’re potted in sphagnum moss, in 50cm tubes. I’m concerned that they’ll rot in this medium - there’s already a carpet of green moss on the surface of each one. However, the last time I repotted a cattleya this size, all its roots died. Can anyone advise me on what to do? Here’s a photo of two of them. The third is the same size.

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I personally do not repot such small plants unless they are actively making a new, healthy growth. Seedlings need to stay moist during warm growing weather, much more so than do adult plants.

In my warm conditions I would need to water plants like that about every 1-3 days, so staying wet too long and rotting roots is not an issue.

You are going into fall now - is is still warm weather? What are your ambient day/night temperatures? Humidity?

[Rross]

Thanks for your reply. It’s winter here in Sydney, which means cold nights - down to single figures Celsius- and relatively mild days - around the mid teens. I’ve got these plants in a warm sunroom, in indirect light. My other cattleyas in that room are actually starting new pseudo bulbs and roots, after hibernating (as it were) all summer in the shade outside. I’m pretty much an orchid novice for any variety except cymbidiums. During the Covid lockdown, I started visiting online orchid nurseries, and now with over 20 new plants, I’m pretty much feeling my way with them.

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My Cattleya and Dendrobium seedlings grow through the winter in my sunroom. Overnight lows aren't that important if the next day is nice and warm.

I think you should leave them in those pots until they begin making new growths. You could repot when new roots are just forming, or leave them in those pots until spring.

Water them lightly so the moss doesn't become soaked, but only damp. If they dry out in a day or two in your sunroom, you can water more heavily, then let them get almost dry before watering again. Even in winter, in a warm sunroom, seedlings should not be dry for long.

Oh, and you're about as far south as I am north - if you have a fan on your plants they will tolerate quite a bit of winter sun through a window. The fan keeps the leaves at ambient air temperature. Without the fan the sun would cook them. My seedlings get about 3-4 hours of direct winter morning sun through a window in the sunroom.

[Rross]

Thank you for your very helpful reply!

[ArronOB]

Three years ago I bought about 50 of those little polypack orchids from the same hardware store - about 30 catts and 20 Oncidium alliance and a few other species. Mostly in May/June.

I left them in their sphagnum mix until spring and then repotted them when the new green roots began to appear. Staying in their sphagnum did them no harm - I just made sure I gave them some really good pour-through rinses from time to time. I’m pretty sure I didn’t loose one plant, and come spring they all responded with stubby little green roots.

When the new roots appeared, and before they were a centimetre long, I repotted them in NZ Orchid Bark (which is unprocessed Pinus radiata bark) in little slotted pots. I think this was around September, but it varies a great deal by hybrid. Again, no issues with this strategy.

I just stand the little 50mm pots in larger pots as those little pots have a great tendency to fall over, especially when the sphagnum gets dry.

Btw, the next year I bought about 30, so I guess that makes it an addiction.

Also, putting your location in your profile allows people to give you much better, targeted advice.

[Leafmite]

If the medium seems new and firm, I agree just to leave the orchid in the pot until there is new growth. I will often poke a few holes in the pot to add extra air for the roots.

If the medium is soft but there is no new pseudobulb with new roots coming and you fear that the roots will rot, the easiest option is to gently remove some of the medium so that more air can get to to the roots.

Another option is to lay out the roots on top of the medium and weigh them down with a rock here and there for stability. Water until the roots turn green. Being completely exposed to the air, the roots completely avoid any infection that might kill them and so they will continue to support the orchid. They will gradually grow down into the medium on their own. I have done this a few times when I have gotten very young Cattleyas that bloom once a year in autumn with broken down bark. The roots have kept growing as if nothing had happened.

[Rross]

Thanks for the advice. ArronOB, my location is definitely in my profile. I don’t know why it’s not showing like other people’s, and I don’t know how to make it show. Anyway, I’m going to take everyone’s advice.

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Once you get the knack of growing Cattleya (and other) seedlings you will be on the lookout for many more! I think your summers outside and winters in a sunroom provide excellent growing conditions for many warm growing plants.

Originally Posted by Rross

...my location is definitely in my profile. I don’t know why it’s not showing like other people’s...

The software terminology is a little confusing. What is displayed in the header of each message is in the menu labeled 'details.' Your 'profile' is what people see when they click on your name.

To edit details, and change what is seen in the header of each of your posts: From the top menu choose User CP then look to the left for Edit your Details.

Make sure you scroll all the way down the Details page. Only some of these data will make it to your messages: Country Flag, Location, Zone (these are US Dept of Agriculture zones, which only apply to North America - Sydney is a lot like San Diego, zone 9b or 10), Orchid Club/Society.

From User CP, looking down the left menu, you can edit your signature. That's how I'm showing a link to the weather forecast for my neighborhood in my signature block.

[Rross]

Ok. Got the flag flying.