Rhipsalis paradoxa overwatering? Leaf browning explanation?

[MBM7]

Hey guys I'm new to the forum and this is my first post. I usually post on Houzz but I've been impressed by the quality of the information on this forum and the combined experience of all of the veteran growers. At this point I mainly keep epiphyllum, rhipsalis (also just got two amazonia wittica cuttings!), and lithops, but perhaps if I stick around long enough I'll also branch out into desert cacti. I'm going to repost a thread I started on Houzz where I didn't receive any responses:

A little background for this question. I recently bought a rhipsalis paradoxa which has been exploding with new growth. True to form, I decided to water the plant yesterday (with fertilizer in water), in the hopes of achieving even faster growth. In hindsight, this was a horrible idea as the plant stems were very turgid, happy, and the particular mix in this pot is not particularly fast-draining. I had run out of my normal fast draining, 5-1-1 (5 parts pine bark, 1 part peat, 1 part pumice) type mix I use on my jungle cacti.

Sure enough, around 8-10 hours after watering I began noticing ill effects in the paradoxa stems. Some stems, if looked at through the light, have brownish splotches inside of the leaf, usually closest to the thinnest, most exterior portion of the stem. Other stems have cracks or little chunks missing where it looks like some insect has been gnawing away. I know that leaves can brown from overwatering, but this behavior seems a little extreme, expecially so shortly after watering. Is it possible that rhipsalis paradoxa cracks its stems after a lot of water for propogation purposes? Many Rhipsalis species have little bits of stem that fall off and then start a new plant. Perhaps the paradoxa has sped up this mechanism when receiving a lot of moisture?

Of course it is entirely possible that this rapid stem cracking/browning is just due to overwatering. I was wondering is someone could give me a scientific explanation why this happens in plants in general, not just in my rhipsalis. I understand tissue death in the extremities of the plant, i.e. leaf tips, when a plant is being underwatered, but I don't understand exactly why this happens in the case of overwatering. I researched this question some online, and the most common explanation is that overwatering suffocates the roots/causes root rot, which I assume results in tissue loss in the plant extremities (leaf tips) as the damaged roots can't take up water well. I have observed this phenomenon, but it usually doesn't happen so quickly after overwatering. Is it also possible that in the case of more succulent plants, cells literally explode from the plant taking up too much water?

For example, I know that very succulent plants such as lithops ¨burst¨ when taking up too much water, but I do not know whether this is from individual cells exploding or rather the plant structure as a whole becoming so turgid that the outer layer of the plant literally cracks open.

Really hoping to understand this phenomenon better from a scientific point of view. I'm attaching some pictures of my rhipsalis! Thanks in advance.

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[mmcavall]

Hello welcome to the forum.
Particularly I don't see any reason to worry, and I don't think it is possible to overwater a Rhipsallis (unless the pot don't have holes below). If it starts to spread and increase, you may considera a fungus or bacteria.
But anyway the plant looks healthy. You may like to cut some pieces and start new pots, as a backup.

[DaveW]

No problem unless the soil gets waterlogged. In nature it gets wet but drains easily being an open medium allowing air in rather than staying a stagnant waterlogged rooting medium. Often composed of mosses and detritus from the trees, or even simply clinging to the bark which stays damp but allow air to the roots. Most of the so called epiphytic cacti are either epiphytic = growing on trees, or lithophytic = growing on rocks. Few grow directly in the deeper soils of the forest floor.

See:-

https://www.youtube.com/watch?v=S7jYUxglNWY

It may also be over fertilisation if the fertiliser was too strong. As you can see in the video the only nutrients they get is probably from rotting leaves etc on branches or in the water running down the trunk. With terrestrial cacti we usually stick to half the strength fertiliser recommended for "normal" plants printed on the instructions and I think epiphytic cacti would not need any more.

The plant looks OK to me, but one of the cracks looks like a stress crack caused by the hanging weight of the stem cracking it on the bend, maybe caused by over exuberant growth from over fertilisation? I would not think you would need to fertilise every watering or it would cause a build up of salts in the soil, in fact leaching the soil occasionally with clean water may help to prevent this?

https://www.gardeningknowhow.com/housep ... plants.htm

[MBM7]

Hey DaveW and mmcavali. Thanks a lot for your replies.

Mmcavali I'll address your thoughts first. I also don't think I have particular reason to worry, the plant is going to be fine long-term. Regarding whether you can overwater rhipsalis, my experience is that you most certainly can, especially when they are not yet very established/soon after transplanting. I grow most of my rhipsalis in fast draining primary bark/pumice/very little peat mixes, and I've had several plants rot after transplanting them from the peat they were bought in.

DaveW thanks for passing along these videos. I was aware that rhipsalis and epiphyllum are epiphytic/lithophytic as you say, but these videos do help to visualize their habitat. The rhipsalis paradoxa I uploaded in the pictures is planted in 50% normal potting soil and 50% pumice, which I know is probably too water retentive and is not the normal mix I use for my epis and rhipsalis.

Your theory about stem cracking because of over-exuberant growth due to over-fertilising is interesting, However I don't think it is the case as like I said, I think I noticed tissue death (little brown stringy splotches) inside of the paradoxa stems soon after overwatering. Several days later some of these brown splotches have sort of come to the surface as little black pockmarks, and cracks due to dead tissue.

In terms of salt buildup, I don't think that is an issue but I could be wrong. I fertilize at 2/5 strength every watering with RO water (every 1, 1.5 weeks during summer). However, I also water until a considerable amount of water has exited the drainage holes so hopefully the concentration of salts never builds up much past that 2/5 concentration I fertilize at. Perhaps my reasoning is faulty here so feel free to point that out. Perhaps it would also be better to fertilize at 2/5 concentration for 2 waterings, and then use 1 watering to leach all salts with pure water since as you say r. paradoxa is probably not a heavy feeder. Thoughts?

As a quick sidenote, I recently learned that pure rainwater has a fair amount of dissolved nitrogen (if anyone knows how much please share!) in it that it accumulates while passing through the atmosphere. So it seems that most plants receive at least nitrogen every time they are rained upon.

Thanks for all of the input! I'm still looking for a response to my question about rot and or cells bursting due to overwatering I asked in my original post.

[MikeInOz]

Hey DaveW and mmcavali. Thanks a lot for your replies.

Mmcavali I'll address your thoughts first. I also don't think I have particular reason to worry, the plant is going to be fine long-term. Regarding whether you can overwater rhipsalis, my experience is that you most certainly can, especially when they are not yet very established/soon after transplanting. I grow most of my rhipsalis in fast draining primary bark/pumice/very little peat mixes, and I've had several plants rot after transplanting them from the peat they were bought in.

DaveW thanks for passing along these videos. I was aware that rhipsalis and epiphyllum are epiphytic/lithophytic as you say, but these videos do help to visualize their habitat. The rhipsalis paradoxa I uploaded in the pictures is planted in 50% normal potting soil and 50% pumice, which I know is probably too water retentive and is not the normal mix I use for my epis and rhipsalis.

Your theory about stem cracking because of over-exuberant growth due to over-fertilising is interesting, However I don't think it is the case as like I said, I think I noticed tissue death (little brown stringy splotches) inside of the paradoxa stems soon after overwatering. Several days later some of these brown splotches have sort of come to the surface as little black pockmarks, and cracks due to dead tissue.

In terms of salt buildup, I don't think that is an issue but I could be wrong. I fertilize at 2/5 strength every watering with RO water (every 1, 1.5 weeks during summer). However, I also water until a considerable amount of water has exited the drainage holes so hopefully the concentration of salts never builds up much past that 2/5 concentration I fertilize at. Perhaps my reasoning is faulty here so feel free to point that out. Perhaps it would also be better to fertilize at 2/5 concentration for 2 waterings, and then use 1 watering to leach all salts with pure water since as you say r. paradoxa is probably not a heavy feeder. Thoughts?

As a quick sidenote, I recently learned that pure rainwater has a fair amount of dissolved nitrogen (if anyone knows how much please share!) in it that it accumulates while passing through the atmosphere. So it seems that most plants receive at least nitrogen every time they are rained upon.

Thanks for all of the input! I'm still looking for a response to my question about rot and or cells bursting due to overwatering I asked in my original post.

I grow quite a few rhipsalis and have never seen cell burst from watering.

In terms of salt buildup, I don't think that is an issue but I could be wrong. I fertilize at 2/5 strength every watering with RO water (every 1, 1.5 weeks during summer).

RO water = no calcium. What are you feeding with? Too much ammonium especially with no Ca can cause problems. Too much shade together with ammonium can cause problems too. You may find a sprinkle of dolomite could help.
Generally it looks healthy to me.

[MBM7]

Hey Mike,

I've likewise never seen this same phenomenon in any of my other epis or rhipsalis. So far it has only happened to the r. paradoxa. I fertilize with a mix of General Hydroponics Flora Gro, Micro, and Bloom, and usually follow their proportion recommendations for vegetative growth. The vast majority of the nitrogen in both GH FloraGro and FloraMicro is nitrate as opposed to ammoniacal nitrogen. FloraMicro contains a good amount of calcium.

Since a lot of my mixes contain a high percentage of pine bark (which tends to acidify the water), I also add dolomitic lime at a rate of 1 cup per 30 liters (1 cubic foot). Having said that, with this mix in particular I didn't add any extra calcium to as it is 50% ph-balanced commercial potting soil and 50% pumice.

I'm going to attach another photo of the browning phenomenon I'm referring to.

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As you can see, the browning starts inside the r. paradoxa stem as sort of fine brown lines towards the edge of the stem. After a few days, the surrounding green tissue dies leaving a black mark on the edge of the stem (also visible in the picture).

[DaveW]

Rainwater does contain nitrogen but tends to loose it in time when stored in a water butt that the greenhouse drains into. That is why putting your plants out in a rainstorm produces better growth than watering later with the same water that has been stored in a rainwater butt. However rainwater is usually better than tap water for our plants if you can store enough.

https://www.sciencefocus.com/planet-ear ... nary-rain/

Is it possible the plant has been infected by a virus? There are a few virus infected cacti known?

https://www.nexles.com/articles/cactus- ... ts-flower/

A section on cactus viruses if you scroll down this link.

https://ucanr.edu/sites/sdsmallfarms/files/172477.pdf

Not in your case, but one of the problems with virus spread into healthy species has been people using virus infected stocks to graft healthy species onto.

[MikeInOz]

DaveW beat me too it. Virus infection is a distinct possibility. Paradoxa and others get cut and propagated over and over and over and passed from one grower to another for years. It is very likely it would pick up some kind of viral infection over the years. If it ever flowers and sets fruit, you can easily start a new virus free plant from seed.

[DaveW]

Depending on how virulent the virus is some plants just seem to live with them and grow and flower with seemingly no ill effects except the virus spots.

I have a 6ft high Trichocereus pasacana that has one and breaks out in a little scab periodically, but still grows seemingly untroubled by it. I have tried various fungicides in case was actually a fungus, but nothing worked. As Mike says the only way then to get a clean plant is from seed, though I believe it can be done by tissue culture?

Seems its easier to get rid of viruses on computers than on plants?

[MBM7]

Dave I checked out the links you passed me along and it looks like it could indeed be the insidious virus X since there seem to be so many symptoms (I say that a bit tongue and cheek)! In any case, it is suffering necrosis which is one of the symptoms listed. Mike what you say about r. paradoxa getting cut and propogated over and over and therefore being more likely to get some type of virus makes a lot of sense. As you say it is probably true of most epiphyllum and rhipsalis species. It makes me want to grow all of my plants from seed but obviously that would be a very slow proccess.

Strangely enough, today I noticed almost exactly the same phenomenon (fine brown lines inside plant leaf, not really visible in the photo), on one of my epiphyllum hookeri cuttings. If the r. paradoxa does indeed have a virus, I'm wondering if it is getting passed around my other indoor plants by the handful of thrips or funghus gnats (not a bad infestation, but they are there) I occasionally see on some of them.

Here is a picture of the rooted e. hookeri cutting:

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Again, there is no rot at the base of the cutting, this is just an isolated patch of necrosis.

[MBM7]

Hey guys, quick update. This morning I inspected the e. hookeri cutting more closely and this brown patch did indeed reach down to the base of the plant (contrary to what I said in my last post), so it was in fact plain and simple rot. I just transplanted this well-rooted cutting into a larger pot and then thoroughly soaked the soil right afterwards. Two days later this full-blown rot appeared, and the soil immediately around the cutting and roots is not even soggy, it's just slightly damp. I'm slowly learning that this is a mistake with most epiphyllum and rhipsalis - you really do have to go easy on watering right after transplanting, even with specimens with fairly developed root balls. It seems counter-intuitive as they are jungle cacti, but I think in nature when bits of stem fall off the mother plant onto another area of the canopy or they have already partially calloused over and they certainly aren't immediately buried in the soil like we do with cuttings.

Observing how the stringy brown bits inside the e. hookeri (what I've also oberved in the r. paradoxa) cutting morphed into what I more easily recognized as rot has led me to believe that perhaps the paradoxa doesn't have any sort of virus, perhaps I just overwatered it as was my initial suspicion. The paradoxa had not been transplanted super recently when I began observing more brown bits and cracking, but it had been transplanted about 6 weeks before and was definitely not fully established in its new pot. That said, I'm not ruling out the possibility of it having a virus.

I guess the moral of the story is that most houseplant problems can be traced back to overwatering, or watering at the wrong time, depending on how you look at it.

[MBM7]

Hey guys just a quick update. I've had the chance to observe the paradoxa over more watering cycles and I'm starting to believe that it does in fact have a virus. The reason I say this is I have seen stems developing the brown lines and then the necrosis even when I'm absolutely sure that I haven't overwatered and the plant has been relatively dry. I also think the e. oxypetalum that hangs right next to it has some sort of virus as well, but there is no way for me to know if it is the same one.

Honestly these viruses seem very hard to control. There is a very small thrips population living on most of my plants and if I'm not mistaken they are vectors for virus transferal. I guess the only way to fully stop insect vectors is with harsh insecticide treatments? Perhaps its either that or just throw out the plant with a virus as soon as you feel fairly certain it has a virus. But that is the difficulty, it is hard to really diagnose a virus with 100% confidence. DaveW as you say it is also hard to throw out a plant affected with a mild virus, because both my rhipsalis paradoxa and epiphyllum oxypetalum seem to be growing well apart from the yellow splotches on the oxypetalum and the necrosis along the edge of the paradoxa stems.

It seems hard to know the best course of action. Plant growing is indeed a journey!

[DaveW]

Moral probably is to disinfect your pruning knives between taking cuttings from different plants.

Also regarding rooting small joints, the chap at Planta Gusto often just lays Schlumbergera joints on top of the soil and lets them root down, not buries the base in the soil. This mirrors what you said previously:-

"but I think in nature when bits of stem fall off the mother plant onto another area of the canopy or they have already partially calloused over and they certainly aren't immediately buried in the soil like we do with cuttings."