Nearly lost two crassulas to root rot (?)

[luvinthemountains]

I don't bother joining any other plant forums, so I ask my horticulture questions here. It turns out that bonsai people are pretty well versed in plant physiology and culture. So, here goes...

About a month ago, two crassulas that I have in bonsai pots - a curly leaf and a gollum - began dropping leaves like crazy, both at the same time. Mature leaves shriveled and fell off, the new leaves that grew to replace them turned black at the tips, and then growth stopped completely. On the curly leaf, this process began in the crown and worked its way down. The gollum lost leaves all over, although to be fair it had a much smaller canopy to begin with.

I responded by stopping my normal watering and fertilizing routine, and when they were thoroughly dry but continuing to suffer, I drenched the soil thoroughly with diluted hydrogen peroxide, twice a week apart. Now they seem to be recovering. The curly leaf jade had enough healthy leaves remaining to generate energy to produce new growth, and there are now juvenile leaves emerging all over the previously bare branches in the crown. The gollum, however, has only a few leaves left which are all damaged, so less energy. But I am seeing little nubs slowly emerge on the branches, so it might come back.

What I am wondering is what I did wrong to cause this disease? Obviously anything any of us come up with will be a guess. But if possible, I want to make sure that I do not repeat whatever mistakes I made.

One thought is that my fertilization regime may be to blame. Each weekend, I alternate between Cal-Mag plus soil inoculant, fish emulsion, kelp extract, and an MSU K-lite chemical fertilizer plus a humic/fulvic liquid. The soil inoculant contains live mycorrhizae, trichoderma, and bacillus, and the reason I use it so often is because my soil is mostly inorganic (lava and DE). I have not been able to find anything in my research to indicate that any of these microorganisms are harmful to crassula. Does anything stand out here?

Another possible suspect is humidity. I have been keeping the plants inside my grow tent, where relative humidity typically hovers between 60% and 80%. Is it possible that the sustained high humidity led to root rot?

Lastly, and possibly in conjunction with the humidity, I am wondering if I might have gotten a pathogen in my tent that specifically affects crassulas? The fact that both plants got sick around the same time, on different sides of the tent, makes me wonder. I do have a fan for circulation that might have spread whatever it was around. The other plants - ficus, bougainvillea, and portulacaria - have shown no signs of distress. Just the crassula.

Thanks in advance for any thoughts you can share!

 

[penumbra]

Always keep them on the dry side both watering and humidity. I have a couple dozen crassulas and in the winter the get water no more often than three weeks ans as long as 6 weeks.

 

[luvinthemountains]

Always keep them on the dry side both watering and humidity. I have a couple dozen crassulas and in the winter the get water no more often than three weeks ans as long as 6 weeks.

Right - I do not water them as often as the tropicals, for certain. But at least a few times a week. I was figuring that with temperatures usually over 90F in the grow tent, intense light and a gritty soil, it would be fine. But that could very well have been it!

I will also say that I have a large c. ovata houseplant growing in my sunny entryway in straight lava, and I water it at least once a week - including during the winter - and it seems to like that just fine.

 

[penumbra]

Get them out of the tent.

 

[luvinthemountains]

Get them out of the tent.

Yeah, I did not mention that before, but that was the first thing that I did. Not wanting to spread any nasties to my tropicals!

 

[penumbra]

Yeah, I did not mention that before, but that was the first thing that I did. Not wanting to spread any nasties to my tropicals!

Its not really an issue of spreading disease as much as it is providing the crassulas with a more appropriate environment. Most of mine are in a 30% humidity ... and dry.

 

[LittleDingus]

Crassulas have a built in water meter. Their leaves get less turgid when they need water. Feel the leaves regularly. When they go a limp and wilty...water them. Otherwise, forget about it. They can get surprisingly limp. I've never seen one die from too little water...they always bounce right back.

Aim for controlled neglect

 

[Orion_metalhead]

If they arent actively growing, I wouldnt fertilize.

In winter inside, I mist my succulents every so often during the week, and only thoroughly water every two or three weeks.

 

[Colorado]

My money would be on over watering in combination with the humidity.

I think that Crassula are not only drought TOLERANT, but actually require conditions that are drier than any other plant I own (other than cacti) to thrive.

I don’t think it has anything to do with the fish or the kelp. I used both on my one “crassula bonsai” with good results. The chem fertilizer raises my eyebrows, I would ditch that. If nothing else it’s counterproductive to your organic ferts.

 

[Bnana]

We're talking about Crassula ovata? Different Crassula species have different care. It would be an achievement to overwater C. helmsii, they can grow underwater.

Your fertilization regime is very complicated, much more than needed. The inocula won't do anything. If the substrate is not suitable they won't establish anyway. If conditions are suitable they're there already.

 

[NOVAbonsai]

I think this has to do with the humidity of the tent. I had a similar problem last year when I had my Jade outside on a deck in the humid Virginia summer which also got lots of sprinkling of rain. I brought some leaf cuttings into a garden center and they suggested it was fungus. I sprayed the plant down with copper fungicide and cut off leaves that were infected plus moved the plant to a drier location and it seems to have recovered. I haven't had any issues since then but I have kept the humidity lower and will keep it from being sprinkled by rain this summer.

Good luck.

 

[luvinthemountains]

The chem fertilizer raises my eyebrows, I would ditch that. If nothing else it’s counterproductive to your organic ferts.

I think I might do that. My thinking had been that organics provide so little N that I needed to use the chemical fert to help growth. Instead, I have seen growth stall in my tropicals, and that may be why.

 

[luvinthemountains]

We're talking about Crassula ovata? Different Crassula species have different care. It would be an achievement to overwater C. helmsii, they can grow underwater.

Your fertilization regime is very complicated, much more than needed. The inocula won't do anything. If the substrate is not suitable they won't establish anyway. If conditions are suitable they're there already.

Yep - sorry, I could have specified. Curly leaf jade and gollum jade are both cultivars of c. ovata. I had never heard of c. helmsii. That is interesting!

As for the inoculant, I do realize that the small ratio of organics in my soil mix (~10%) mean that they will not colonize the soil itself. I am applying frequently in attempt to colonize the root tissue. I allow that I am probably not understanding the mechanics very well.

 

[luvinthemountains]

I think this has to do with the humidity of the tent.

Seems you are probably right. My fault for getting greedy and wanting to push growth over the winter with artificial light. They did grow, too, but only until the root rot set in. Lesson learned, I guess.

 

[Bnana]

These inocula are pretty useless, no matter what soil you use. I wouldn't waste my money on them.

 

[AlainK]

As for the inoculant, I do realize that the small ratio of organics in my soil mix (~10%)

"inoculant" : Micorrhyza can be useful for most outdoor trees, but it's useless for Crassula.

"Crassulacea" are not pines or maples.

Sandy loam, or a mix with fine particles (they have fine roots) with 30 to 60% of organic soil is a lot better.

Which reminds me I must soak the pot of this one that I repotted in December 2020 in the kitchen sink : haven't done it for two weeks, indoor temp. around 20°C and very dry, poor light so the "branches" go leggy and droop when the plant is thirsty.

 

[Bnana]

I'm definetly not saying mycorrhiza aren't useful, they clearly are. These inocula are not. Mycorrhizae will get there anyway so no need to add them.
Furthermore these inocula contain the mycorrhizal fungi that are easiest to grow, that is very likely not the best one for you still and tree species.

At least some Crassula species form associations with arbuscular mycorrhizal fungi. But it is near impossible to keep those out of your pot anyway.

 

[cbrshadow23]

I bring several of my crassula into an indoor grow tent each winter and get lots of leaf drop. It doesn't have to do with watering schedule or humidity (I track both in the tent and outdoors) but has to do with a sudden change from its previous conditions. Portulacaria Afra do the same thing. If you change the intensity and duration of light that the plant gets, along with temperature changes, the plant drops most of its leaves and pushes new leaves that are adapted to the new conditions. The same thing happens in late spring when the plants go back outside.
I've had this happen with many plants many times, so I expect the leaf drop. The plants end up growing a ton.

One other point: I think folks here are assuming that your tent is a closed system without intake or exhaust, which would trap humidity. That's not the case with grow tents. The humidity should be the same as the room that it's in, even if you water your plants in the tent. If your tent is sealed and air tight you're going to run into issues.

 

[luvinthemountains]

I bring several of my crassula into an indoor grow tent each winter and get lots of leaf drop. It doesn't have to do with watering schedule or humidity (I track both in the tent and outdoors) but has to do with a sudden change from its previous conditions. Portulacaria Afra do the same thing. If you change the intensity and duration of light that the plant gets, along with temperature changes, the plant drops most of its leaves and pushes new leaves that are adapted to the new conditions. The same thing happens in late spring when the plants go back outside.
I've had this happen with many plants many times, so I expect the leaf drop. The plants end up growing a ton.

One other point: I think folks here are assuming that your tent is a closed system without intake or exhaust, which would trap humidity. That's not the case with grow tents. The humidity should be the same as the room that it's in, even if you water your plants in the tent. If your tent is sealed and air tight you're going to run into issues.

Hmm. These two were in the grow tent for about 3 months before any problems arose.

I think that the tent setup I have does tend to be a fair bit above ambient humidity. There is a 100cfm exhaust fan, but it only comes on when the temperature exceeds 105F. I rely on the negative pressure to draw fresh air through an open panel. Plus the tent gets opened every day or two for watering, which releases pretty much all of the stored humidity.

 

[Carol 83]

Portulacaria Afra do the same thing. If you change the intensity and duration of light that the plant gets, along with temperature changes, the plant drops most of its leaves and pushes new leaves that are adapted to the new conditions. The same thing happens in late spring when the plants go back outside.

I have never had that happen with mine. But I don't have a grow tent. Just bring them inside and put them under lights. They don't lose leaves coming in for the fall or going back out in the spring.