Hello,

I have some SP seedlings that are probably a year or 2 old now (bought them as established seedlings about 6 months ago), and they have been doing fairly well. However, about 2 weeks ago half of them started slightly turning color and softening.

It started with pale yellowing all over, not really localized. I had never fed them, so decided to give that a try a dry organic 3-4-4 at about 25% of what they were recommending for established plants. Now that pale yellowing is turning darker, and they are getting bendy. In the middle in the pic, that section bends very easily.

I have been watering them once a week. They are in a cactus soil that I supplemented with more perlite. They were watered on Monday, and the soil just under the surface is moist feeling, but far from wet.

They were typically indoor until around a month ago, but we've been having 70F during the day, 50F overnight, so I left them out this whole time.

The pot is way too large which in all probability lead to a watering issue. Cactus do not need to be watered weekly. Cactus soil was a good choice which I think was largely negated by adding perlite which holds water.
I think it has rot and it is dying. I don't think it will survive.

Cactus soil with added perlite is good. Perlite opens air spaces so allows the soil to dry more quickly. Cactus roots need a dry period between watering. Your problem is overwatering. The soil should be dry almost to the bottom of the pot before you water. Your pots are large - once a week is way too much. An appropriately sized pot is just larger than the root ball.

Fertilizer was a bad idea. Its not medicine. When you fertilize stressed plants, it causes more stress.

Makes sense kinda. Although two opposite opinions on perlite in the two responses...

I added ferts during the yellowing because in my experience with other plants (new to cacti, but advanced from decades of growing leaves) yellowing the way I saw it a couple weeks ago is a sign of nitrogen deficiency (again, in other plants, maybe its different in cacti?). Typically I would mix in our own chicken manure (we raise chicken to supplement low N in our home soils) but I opted instead for a very mild organic fert that I cut in quarter. With the amount I used, not sure it made a huge difference honestly, but any Ill skip that too. May be different for cacti it seems.

Guess if it dies, it dies, unfortunate but lesson learned. However, Ive definitely pulled many plants from near death before, pretty confident Ill get it worked out. Somehow I always end up fixing the issue one way or another.

Do you see the "Suggest a Change" link just below this text box? Ask this thread be moved to the Cactus and Succulent Forum. You will get better advice there.

Vermiculite and those gel beads hold water. Perlite holds air. It's why it drives me nuts by floating to the top of the soil after a while.

I concur with the conclusion that overwatering is the culprit.

With cactus seedlings, use tiny pots and prepare to be mean. I don't water my young/small cacti until they start to pucker or shrivel.

Ive always used perlite for increased drainage, so I was surprised to hear that comment above.

I transplanted into something smaller now, and replaced the soil with a bit I have that is slightly drier. Movement on these has been pretty quick, so Im assuming Ill see in the next 2 or 3 days if this had any effect or if it was too late. Fortunately I have a dozen or so others doing just fine, but two or three not happy. Dont like losing any plants, and unfortunately, thought I was ignoring them enough, but didnt think of the container being too large. The soil fully dries in the direct sun in about 5 or 6 days (these last couple weeks anyway), but I didnt think about the bottom half of it.

Small pots it is.

Guess well see. Thanks!

I use it in my orchid mix. And yes it improves drainage by helping to keep the mix open so it doesn't compact. I use it because for me it holds water and does not break down like fir bark.
When you grow a good deal of orchids like Phragmipediums and Paphiopedilums, it has really improved my mix. My plants stay wetter longer, and their root growth has improved dramatically. The orchid roots cling to it much more then charcoal or aliflor which are also part of my mix.

That is the only time that I use it. I have been using it for 12 years now.

In general my mix has around 20% perlite in it. Individual pieces are 1/4-3/8".

When you moved your plants outdoors, how much exposure (sun) did you give them?

They honestly got a lot, and I worried it may have been too much too quick. Probably 12 hours direct. Odd thing is, 75% of the them have flourished in this new environment, ferts and soil, with only a few looking like this.

Been thinking of maybe moving them into an area with only 3 or 4 direct in the morning, and shaded (still with ample sunlight, just not direct) for the remainder of the day.

Mind is blown that cacti could be this opposite from what Im used to, but its definitely a realm Im not familiar with. Large pots with soil to expand in, great sun and a small, gradual addition of nutes has always worked for me in the past, out of my element here for sure!

Too much sun too fast. You need to provide a gradual stepwise introduction to direct sun if plants are coming from indoors. This has to do with the way regular window glass filters out most of the UV in sunlight, making indoor sun much kinder to plants. They need time to build up UV resistance, and the sun is almost certainly the trigger for the color change, perhaps exacerbated by other things (the fertilizer or whatever). To the extent some plants are apparently doing fine, you should be all set with them. To the extent the others are melting down, they are probably lost at this point. Maybe you can try moving them to bright shade to see if they recover. But now you know for next time, indoor sun and outdoor sun are not interchangeable... go slow when making the transition to the latter.

Eh, oh well. Live and learn. I'm pretty good at keep plants alive so I doubt they're totally done, but I'll buy some backups anyway to supplement these ones just in case. Liking the seedlings so I'm trying to get a few every month to fill up the property eventually.

It's only like 2 or 3 of the dozen or so I have with this issue, so something was up with these ones in particular, but they also had a slightly different look when I got them. One of them was a runt when it showed up too, and that's one of these as well. But I had another 4 or 5 that FLOURISHED under these same conditions, bought at the same time. Plants are finicky sometimes I guess, or maybe they were just more resilient and these couldn't hang. Either way, I'll reduce direct light (after tomorrow, I'm going to have them dry out a bit, then move tomorrow afternoon),and let them indirect for a while.

We'll see.