If it's getting quite a bit of direct sunlight, I think it might be sunburn. Beware of direct sun after raindrops because the "magnifying glass" will surely burn the foliage, especially if your plant is kind of new to direct sunlight. At least that's what I think it is... I don't think it's rot so it should not be too bad

I wondered a little about that myself, but it's been outside all summer. In fact, it had recently been getting less sun, and my other C. tetragona that's been in a pot right next to it doesn't have the funk. The one day we had any rain all summer might have done it. Maybe the water got knocked off the other one. Thanks, David.

Rain won't actually cause a "magnifying glass" effect....that old myth has been fairly well debunked.

Josh

UPDATE:
I pinched the damaged top off the affected plant and tried to root it. It just keep dying from the stem upward. Right now those top green leaves and little new branch are still alive, but no stem below it.

The main plant is still the same - no new damage - and there are tiny buds where I removed leaves. But, my other C. tetragona, in a different pot, and inside since this happened, also has the brown "stain" now. It isn't nearly as bad. Nothing is dying, but it's the same damage, just to a lesser degree. It is inside, and hasn't gotten wet, so it isn't water spot. I think David is probably right about sunburn, but I'm having trouble understanding WHY. It spent the summer outside and had at least 4 hours of direct sun daily. It is now inside in a south-facing window, probably getting 4-6 hours of direct sun, BUT, it's cloudier these days. Why would it burn with just maybe a couple more hours of sun daily? The Echeverias, Pachyverias, Graptopetalum, and other Crassulas aren't burning, and they'd had less time to adapt. I'm baffled. Could it be that the tissue is more susceptible from having been almost, or just slightly, sunburned before?

I'm not really sure what to do about it. Should I leave it to sort itself out - let it lose what it will and regrow what it needs? It looks pretty crappy right now, but eventually it'd lose those lower leaves as it got big anyway, so I know it isn't permanently ugly. And the new tips and leaves look nice. I do worry about stem damage though - I assume that's why the pinched stem from the other plant rotted rather than rooted.

I just love this plant. It lends itself so well to shaping, and I've been looking forward to playing with it. The cuttings are easily 3 times the size they were when I rooted them about 8 months ago, so I must've been doing something right last winter.

Any ideas and insight are welcome.

Hey there,

I've actually been having the exact same problem with my tetragona. It started showing up after I ordered it online and placed it in a north-facing window, so it's not sunburn.

When I looked really closely at the stems, there were several small black dots moving around, indicating some kind of pest. I used an insecticidal soap spray to do several treatments. Since crassulacae don't really love insecticidal soaps, it caused several of the already infected stems to lose their leaves. However, all the black dots are gone, and there is new growth on all the stems. I'd check to see if there are pests on your plant, because it looks exactly the same as mine did before spraying it! Hope you get it figured out.

This is a full-sun plant, once it gets acclimated. Assuming you've got it in porous soil (although that doesn't matter a great, great deal as this is a fairly easy plant to grow and adapt) and you're not watering it too much, you're giving it warmth and adequate air circulation, I'd guess it's not enough sun it's getting.

In my experience, the plant isn't picky about temperature. It rooted and grew great last winter between 40 and 60 degrees. It was also not getting much sun in a motor home in the woods in the the hills of gloomy western Oregon - so dark that I put a mirror behind it to increase the light - yet it grew great.

It had all summer to adapt to lots of sun. It's in pumice only. I can't find any pests, even with a very strong magnifying glass. It is definitely getting adequate light.

I still think David's sunburn hypothesis is the most plausible. Why, is the question. Too much fertilizer? Too dry in the pumice? Both those things would make it more susceptible to sunburn, but a pothos in the same substrate, with the same fertilizer, in the same window is not sunburned, but it hasn't been in the window as long - 10 days vs. 25 days.

Perplexing.

A rain shower followed by high sun does increase UV rays iIt's the ' magnified ' change in UV that helps plant foliage and in some cases thin smaller branches to burn in short time.

If the changes in sun UV is the culprit whats difficult to understand is why it burnt in the middle and didn't burn on the top.

Assumption to it being overly dry in even pure pumice as there is new growth I'd would suspect a root problem of some type.

I've been trying to determine what was wrong with this Crassula tetragona since May. Had suggestions for drainage, potting mix, sunburn, etc., but just one person suspected pests.

Pallas Athena, you have spider mites too. Did yours recover?

Remember how this looks and progresses so you can protect your own plants.

Mites aren't visible. I couldn't see them even with a magnifying glass. I needed the macro lens of my "real" camera, then I had to enlarge the image.

It begins as yellowing of leaves for no apparent reason. Old leaves are mostly affected, but newer leaves sometimes also. Leaves drop. Some shrivel. People mistake it for over-watering, poor drainage, sunburn, etc. As it progresses, leaves look textured with tiny indentations about pin pricked size. Leaf surfaces get what looks lime a brown or black coating, stain, or discoloring. Plants continue to grow and produce more leaves and branches, but eventually only those newest leaves remain healthy.

That's where my plants are now. I can save them, but it'll be a huge setback. Worse, they've been in contact with all my other plants, shared a wager bucket, etc., so I'll be treating a lot of plants. Hopefully, this mite doesn't thrive so well on other plants.

Update: I washed it in alcohol and dish soap, and wiped all the areas I could reach with a Q-tip. Many more leaves came off as I did it. I don't know if thatll be enough, but I can't find any evidence of other plants also being affected, so I hope it was just this one plant the little b******s liked. I don't want to resort to nasty chemicals.

This post was edited by kwie2011 on Mon, Oct 27, 14 at 16:59

So sorry Kwie that your having these problems!! I hate pests!!! ð¡

Did you have mites in May as well as warmer air?
Warmer air warms soil and can build up inside of pots to cauce a steam sanua effect that also warms roots to a point where they( in a sence) 'stem' better than breath.

I'm pretty sure I bought the cuttings already infected. It just wasn't bad enough in May to make that tar-like stain. Mites were why old leaves were pale, yellowing and dropping. I'd posted in the houseplant forum, but couldn't upload a photo.

These mites are TINY. Much smaller even than thrips. I couldn't see them even with a magnifying glass. There has also never been any webbing on the plant (that I could see). Most sites say webbing is one way to ID mites, but maybe this species is too small.

It appears none of my other plants are affected. I'm hoping the mite is species-specific. I have about 50 plants, and can't go over every inch of all of them with alcohol and dish soap like I did this little jade. I'll repeat the alcoholic and dish soap wipe every 3 days for a couple of weeks to be sure I kill any new mites that emerge from eggs.

Jade survived its treatment. I half-expected rubbing alcohol and soap to kill it. It is tough though. Despite the mite infestation, it has grown at least 4 times its size since last spring.

Thanks for the sympathy, Christy. This is the first time I have ever had pests in my memory, and out of about 50 plants, I only have 4 that aren't growing as well as I'd like, so I can't complain. Did you ever determine whether you really had root mealy bugs, and were you able to fix the problem? My Bantel's Sensation offsets are FINALLY rooting by the way - no bugs, thankfully.

Double post

This post was edited by kwie2011 on Tue, Oct 28, 14 at 17:05

I think my problem on the aloes was not letting the roots callus b4 watering. The one had what looked like white mold by the roots but I didn't actually see any bugs. Even though it wasn't near any of my other plants, I chose to treat EVERYTHING with what Al had recommended and so far so good. I'd rather be safe than sorry. I might of overreacted but I really hate loosing ANYTHING. LOL and I REALLY HATE BUGS!! Lol I'm sure you agree.
And YAY on your Bantels!!! I'm glad they finally took.