Wednesday, July 13, 2011

Question for the Hive Mind: Crassula ovata

I am beginning to think that maybe the entire Crassula genus is just not for me. First there was all that business with C. rupestris and C. muscosa, and my C. arborescens is acting weird lately (dropping leaves, not growing), and now the parent C. ovata from which all my other C. ovatas come is being strange.

There are two things going on, one I think I understand and one I don't. The one I think I understand is this:


To me, this looks like a fairly open-and-shut case of fungus or mildew (also a fungus) or whatever. I don't really understand how it happened -- the plant in question is in a spot with better air circulation than the cuttings I've taken of it, and similar temperatures and humidity, but the cuttings are fine. I'm not happy about it, at all, but I feel like I understand it.

The one I don't understand is this silvery/cracked thing, which is happening on the same plant:


We used to get questions about this at the garden center every once in a while, and I never knew what to say. The plants we were selling did it occasionally, but it never affected the whole plant at once, it happened at about the same rate year-round, and it went away on its own, so I never developed much of a theory about what was going on.

Since my plant is doing it now, it's occurred to me that maybe I could ask y'all for theories about what's going on. If it helps, the plant was bone-dry when both of these things happened. (I pulled it out to check the roots. Not only was the soil completely dry, but there weren't nearly as many roots in it when I pulled it out as I know there had been when I first put it in that pot.) It had been in a west window, where it got some direct sun in the afternoon. It was watered about every four to six weeks, and was in a plastic pot. (Which is why it was only watered every four to six weeks -- it seemed to stay wet forever.)

I'm sure someone out there must have an answer about what this is. And if you could work in a cure that would also take care of fungus at the same time, that would be awesome. For the moment, I've put it outside (under a chair -- we don't have suitable shady spots), on the theory that the extra light will either vaporize the fungus or kill the plant outright, which solves at least some of my problems either way.


15 comments:

Anonymous said...

Not that this is any help, but for a few drastic cases I have found that "kill the plant" was my best solution. I like Crassulas myself but none of mine have had anything resembling your problems (they have had their own weirdnesses, esp the ones that summered outside). I do think that the fact that the plant is losing roots for no obvious reason is potentially a clue to some systemic failing. I'll watch for answers from more insightful readers.

FundyBay

Paul said...

The whiteness leads me to think it's something like sooty mold, but with no obvious insect vectors, I'm stumped.

I would dust it with sulfur and try a systemic fungicide, like bupirimate.

Liza said...

If I just say "ew," that's not very helpful, is it?

stefanogiovannini said...

Growing some from cuttings and they seem to do well. Put them on the roof. Hot and breezy all the time.
Probably indoors was too humid and the fans may make the fungus spores travel.

I am sure the sun will take care of the problem. Maybe I would remove the most diseased leaves. But I wonder if fungus spores survive the dry heat.
I would change the medium also. In what medium is it?

Paul said...

Can't help you, I'm afraid. Perhaps the folks on the Cactus forum at GW might be able to help?

Pat said...

Crassulas love to be underpotted. If it was staying wet for so long then it is in too large a pot and perhaps not well-drained enough. The small plants have more tolerance for this but when they get bigger they suffer. Leaving C. ovata bone-dry over winter (end of October to beginning of April) not only keeps them happy but encourages them to flower.

If you do feed use a weak feed much higher in K and P than N.

grumblebunny said...

I'd probably put it in a pot where the soil dries out faster -- in my wholly unscientific observations, crassula ovata roots like to sit in parched soil that reminds them of their dessicated homeland. Too much unneeded moisture for too long and the roots mope. My clumsy program for success: When the fat little leaves begin to soften, I give the plant a good drink to fill 'em up again, then leave it to its desert dreams until it's time for the next refill.

Thomas said...

Looks like fungus, or a late night raid on the powdered sugar doughnut holes. Do you have a fan in your growing area going 24/7? Since they transpire at night due to CAM I'd wonder if good air flow then might benefit, and maybe assist in gas exchange. Probably would want to clean it off first (w/ Neem?) to minimize spore spread.

My first thought when I saw silver-crinkly was sun damage, espec. isolated on the top(?) leaf. Was something recently shifted in it's neighborhood, or a change in the angle of sunlight?

Could try some Aloe vera (joking...)

mr_subjunctive said...

To answer questions:

There is a fan in there, running all the time.

Leaves with the powdery thing fall off on their own if touched, so cleaning the plant off would probably have to involve spraying the whole plant (and soil?) with some kind of fungicide.

The plant gets stuck in new positions when it's watered, but nothing dramatically brighter or darker for the plant overall, aside from the days being long.

I did repot the plant before putting it outside, since it obviously didn't need as big of a pot as it had been in, not having that much for roots. If I remember correctly, it went from an 8-inch plastic pot to a 5-6 inch clay.

Sentient Meat said...

Could the plant have some small pests? That crusty surface in the second picture reminds me of cyclamen mite / broad mite damage in other plants. And if you have tiny, sucking insects, they could be promoting the fungus (from the honeydew they secrete).

Pat said...

Could you post a photo of the plant in its pot as it is now? Just so I can get an idea of the size ratio.

This one I would repot by an inch, the one on this page will be fine for a few more years.

It is a good idea to put a few cobbles in the bottom of the pot as they get so top heavy.

Tracy said...

Was there any discoloration on the roots that were remaining? I would have to guess the fungus is systemic if that is the case and causing many if not all of these problems. If it is a systemic fungus and not something that is just attacking the leaves then a systemic fungicide may help or it might be game over for that plant.

mr_subjunctive said...

Pat:

I'll try to get a picture up soonish, though you'll have to keep in mind that the root system is still much smaller than the size of the new pot. (There's no way I could put it in a pot that would leave the roots crowded without it being unacceptably top-heavy.)

Tracy:

Not really. They were all kind of tan/gray, and looked normal as far as I know what normal jade plant roots look like. Which is not very far.

stefanogiovannini said...

what about a shallow azalea or orchid clay pot, some broken pot/ gravel in the mix. Will not be top heavy. I am sure it would be happy in gravel/ grit mix. Anyway I would dunk it in H2O2 to kill fungus and bugs.

The Ubiquitous Mr. P said...

Hi, thinking you need soil that dries faster and you may need to treat the leaves with something like tea tree oil.

Good luck!