Species Cattleya new growths dying
 

I have a Cattleya warscewiczii coerulea I got from Orchids Ltd back in 2020. Super vigorous grower!

Occasionally, though, a new growth will shoot up, and once it's a few inches tall it will turn dark brown / black and start dying back.

Any idea why? Pics included.

I grow it indoors year round (New England), dryer in the winter, wetter in the summer. Growing in sphagnum since I got it, repotted it last summer into fresh sphagnum.

This also occasionally happens on mature leaves, but much less frequently (last image). And when it does, I cut the leaf to the top of the pseudobulb.

https://i.imgur.com/0PvCQxa.jpg

https://i.imgur.com/sBdYtyI.jpg

https://i.imgur.com/SABPvtj.jpg

https://i.imgur.com/THnmACR.jpg

https://i.imgur.com/VKiJcrV.jpg

https://i.imgur.com/Az181SW.jpg

I would seriously question the use of sphagnum for a Catt, especially a relatively mature one (might be OK for seedlings) If those new roots are just showing, would be a good time to repot into a better-draining medium.

It is possibly Calcium deficiency. Add a source of Calcium (oyster shell, Cali Mag, powdered milk). Some Cattleyas/Laelias seem to need more Calcium than others to be happy.

https://staugorchidsociety.org/PDF/O...ySueBottom.pdf

That makes sense. I got this one in a 5" pot, it's Cattleya warscewiczii coerulea 'Angarita' x self. I've kept it in sphagnum because Orchids Ltd. seems to grow them in sphagnum just as regularly as they do bark (YouTube link below), and my home has low humidity so my plants dry out pretty quickly and the sphagnum means I have to water a bit less frequently.

Does that all still sound okay to repot it in bark in a plastic pot? Tall pot or short pot?

And is the black new growth from the plant being too moist?

YouTube example:

https://www.youtube.com/watch?v=usyZdhC6AvY&t=1s

A bunch of issues here... Is it potted in pure sphagnum, or is that a top dressing?

How are you watering your plant in sphagnum? Thoroughly soaking it? How do you decide when to water?

The shoots are probably dying because the plant isn't getting enough water. What you show is classic for Cattleyas underwatered while making new growths. The new roots look good. That suggests to me the roots inside the pot are dead. Watering in sphagnum is very different from watering in bark.

Are you giving any calcium in your water or fertilizer? That can do this too, as Leafmite wrote.

Thanks for this!

1. Yes, it is potted in pure sphagnum.
2. In the summer, I water it around when the top is cruncy dry and the pot feels noticably lighter. In the winter I let it be crunchy dry for a few days. When I water it, I pour probably 1-to-1.5 cups of water into the center, and when I come back a couple hours later that has typically diffused out to make the edges moist (definitely not soaking).
3. No I am not adding calcium to my water. I very rarely fertilize anyway, and if I do I use a weak amount of MSU.

If you think bark would manageable for my growing and much better for the plant I would definitely do it.

Your watering method is probably OK while in active growth but it probably needs more water. During the winter this species needs almost no water.

If there is no natural calcium in your water that might be the problem. MSU doesn't have much. Consider fertilizing at least weekly while growing, or adding a calcium supplementation.

I would also gently pull back the moss to try and see whether the roots are OK. They may not be.

Thanks for this!

I'm kind of inclined to repot it in orchiata large(?) bark and a tall-ish pot (like in the video). What do people think? Is that a good idea?

My thought is those new roots are probably the only good roots the plant has. Most people who advise to wait to repot until the plant has new roots would also say you need to do it when they're very small, and if they get this long, it's too late. If you repot it, there is a substantial risk you'll damage the only good roots.

I totally agree with ES... don't repot. Let those new roots grow. If it climbs out of the pot, that's just what Catts do. Next year you can repot when the plant is stronger, and you can catch it just as new roots start.