Potting mix for Catt. seedling

[Rhonda Svoboda]

Hi,
I have two mixes that I can use for this orchid. Its a catt. seeling. I have a straight Catt. Imperial mix and an oncidium/seedling mix- both from RePot Me. Which should I use? It came in a spagh./bark mix.

[Roberta]

I'm not familiar with the details of these mixes, but look at the end result that you want... well drained with lots of air and the ability to dry out somewhat between waterings. (Not bone dry but drier). My guess is that the Oncidium mix will be very water-retentive, not what you'd want for a Catt. (Oncidiums like to stay fairly damp, Catts like to dry out somewhat) How big is the seedling? You also want t match medium size to the plant and the pot. And most important, is it starting to put out new roots? The last is really vital - new roots will adapt themselves to the medium that they grow into, older roots may decline or die if the new medium is drastically different than what they developed in.

[estación seca]

Choice of potting mix depends on your growing conditions and how much time you have each day. Every gardener of any kind of plant faces this issue.

The best way to grow Cattleya seedlings is in very large chunks of something that doesn't shift in the pot, combined with warm temperatures, high humidity and daily watering.

I still haven't found somebody to keep me, so I need to work. I can't get to my plants every day. My sunroom is sometimes fairly cool in winter. So I can't pot Catt seedlings the way I mentioned above. Everybody has to compromise.

Try to pick a pot/medium combination that dries out completely in your conditions in 4-5 days. I can't be more specific because I'm not in Michigan.

My experience has been more Catt seedlings suffer from not enough water rather than too much water. Of course, there must always be air at the roots. I think Catt seedlings use more water than most other kinds of orchid seedlings.

I think tightly packed long-fiber sphagnum moss can be great for Catt seedlings. The goal is never to completely soak the moss unless the seedlings is using so much water it goes dry in a few days. My experience with Laelia purpurata seedlings growing in warm conditions has been that sphag gives me the best results.

But sphagnum isn't a good choice for seedlings kept outdoors and subject to frequent rain; it gets so soaked there's no room for air. Plus you need to learn how to water with Sphag. It's very different from watering bark mixes.

I have found that with my conditions, semihydroponics works well for larger seedlings, but not tiny ones. The LECA moisture level in containers in my sunroom is too low for tiny seedlings. If I could water them every day, or if I had nearly 100% humidity, it would work. But those aren't my conditions. So I leave tiny seedlings in pots until I think they're big enough to move to S/H.

Start by figuring out how often you have time to water your seedlings - summer and winter. If you can get to them every day or two, use something with larger particles and a smaller pot. If you sometimes have to let them go a week between waterings, use medium with smaller particles, and maybe a larger pot. Exposing them to rain outdoors is fantastic if the potting medium retains air even when very wet. Plants in S/H would love heavy rain all summer, but, as I mentioned, plants in tightly packed sphagnum would not.

I'm not too familiar with the mixes you mention. I looked them up online. I would consider the Imperial mix if you can attend to your plants more frequently, or for plants outside in the rain. The Oncicium/seedling mix would be good if you need to let them go more than several days between waterings.

[Rhonda Svoboda]

Thanks to you both. I picked an airy mix (the catt.one) which had bark about the same size as it came in. I added a bit of spagh. to retain moisture but not so much as to smother the roots.