M. luethyi--clusters rotting?

[tomo]

My M. luethyi has been growing like crazy the past few months, and after doing some research, I recently realized it needed a LOT more sun. I gradually started moving it into the sun a few hours every day, and at about the same time, I noticed one of the little clusters started turning brown. Over the past few weeks, more of the clusters strated turning black. Today, I realized they were actually rotting, so I gently scraped away most of the mushy clusters (and I'm hoping I can save the last two, which so far seem untouched).

So what happened? Did it rot from too much water? too much humidity? too much sun? all the above/none of the above?

Any advice to save it & tips for future luethyi care would be much appreciated.

[iann]

I don't like the black on the stock.

[Onzuka]

Yes, not nearly enough sun. These are brown with the white tubercle ends almost touching when grown correctly. Maybe you allowed water to stand where the grafted parts were dense.

I would cut some of the rotted stock off to see how deep it goes. With luck it will be very shallow. Wipe the wet areas with kitchen paper and try to get them dry, a bit more scraping of the rotted bases may be needed. Get it in a well ventilated place to get the damaged areas to callous over. Keep the grafted joint dry and you may be lucky.

Steve

[tomo]

Hmm, I was so worried about the luethyi rotting, it hadn't occurred to me that the stock might be rotting too (or I guess even the cause of the problem?).

I would mist the luethyi from time to time, and then water the soil when dry, about once a week--I'm trying to figure out if I over-watered and that caused the rotting. It's frustrating because it was growing so fast (even without enough light).

Steve, I don't quite understand (I'm a beginner, so pardon my ignorance )--I should cut the rotted stock off, cut the Luethyi off, let both dry and callous over, and then try to rejoin them? is that right?

Thanks for the replies, really appreciate it.

[george76904]

I can't advise you on the best course of action, but the reason it was growing so fast was because it didn't have light. Notice how long the space between the areoles. It is etoliating which means that its stretching out trying to reach more light. Unfortunately the etoliated growth is very weak. Misting it is could actually be what could have caused the rot. Or a fungal infection caused by a nick in the skin.

[Steve Johnson]

I would mist the luethyi from time to time...

Sorry, but not a good strategy for any grafted cactus since it invites rot along the rootstock/scion juncture. Water around the base of the stock, keep that juncture dry, and if your current effort fails use this as a "live and learn" moment and get another grafted luethyi if you can. Or better yet one on its own roots, although there may be a good reason why the species does better on a graft.

[Onzuka]

Steve, I don't quite understand (I'm a beginner, so pardon my ignorance )--I should cut the rotted stock off, cut the Luethyi off, let both dry and callous over, and then try to rejoin them? is that right?

NO! That would be a very high risk strategy for a cacti beginner, but quite likely a good one for a more expert grower and grafter.

Take a shallow, sloping cut from the base of the graft to the edge of the Harrisia rootstock, avoiding the actual part where the two plants join. If you are lucky, you will have healthy green tissue. This will show you the extent of the problem. If the 1st cut is not enough, take some more off. The outcome you want is a healthy rootstock, then all of the problem is what you see and have tried to clean up. Wipe the damaged area as much as you can and scrape away as much of the brown tissue as you can, its dead and rotting anyway. Dry it again and get it somewhere warm and dry. The damaged areas will callous over and heal.

In future, give it good light and just water the compost. Harrisia is a tough rootstock and will stand much abuse, but its not bombproof. Treat it to a drench and dry regime, much like most cacti.

I wish you good luck, but if the worst happens, put it down to experience. Sod's Law always applies and these things happen to our best , rarest and most favourite plants.

Steve

[iann]

Perhaps growing in the dark and being wet all the time isn't good for M. luethyi

Whatever you do, you need to get rid of all the discoloured flesh. If that means chopping it up then you'll have to do it.

[tomo]

Thanks for all the replies. I had no idea misting was such a no-no for grafted cacti--well, live and learn.

Steve, thanks for the detailed explanation. I made the cut, and it was green underneath. I tried to scrape away as much of the rotten parts I could. I'm not sure if it needs more scraping, I was worried about damaging where the luethyi is grafted. Of course, it may be too late, but I'll see what happens, and as you said, it's been a learning experience.

I think I figured out what caused the rotting (as well as the misting). When I removed the luethyi from the pot, I noticed the soil/granite mix towards the bottom was very damp. Which is weird, because every week the top part would dry out and look completely dry. So I'd water it again, not knowing the roots were still damp. I also think I used a pot that was too big.

Honestly I'm kinda bummed because it's one of my favorites. But I plan to order a new luethyi (or maybe 2) so even if this one doesn't make it, hopefully I'll know what to do with the next one. Thanks again everyone.

[iann]

If the roots didn't properly penetrate the bottom of the pot, it would stay wet. I'm not sure that is the problem though. The stock looks pretty healthy apart from the graft junction. I think the scion went and is doing a pretty good job of starting to rot the stock.

I don't think you've cut enough. That isn't a good colour, either at the base of the scion of the top of the stock. Maybe it is just dirty, but certainly it needs close inspection.

When M. luethyi rots, there isn't much left, but it is possible to graft individual tubercles. I suspect it isn't easy though.