Why have so many of my cacti died this winter?

[Shane]

It seems like every time I go out to check my cacti, another one had died. This has been happening for months and I have no idea why. The last two winters I didn't know how to properly overwinter cacti left them in the rain and had no deaths. This year I've been keeping them dry and they've being dying left and right. have no idea why doing things the right way has produced such poor results. It's very frustrating. The highest fatality rate is among plants I "freed the roots" in (Removed the peat soil that the plant came with and replaced it with cactus soil. Before this I just put the whole root ball with the peat into my cactus soil). About half of these plants have died. I thought this was supposed to be good for them. I'm so frustrated

I thought I was doing things the right way but I'm getting very bad results. What am I doing wrong?

The cause of death isn't clear. The flesh turns kind of yellow and eventually dries out. Here are some pictures of dead and dying plants

[One Windowsill]

How long before winter did you change the compost? Did they have a chance to recover, heal and grow new roots?

[Shane]

How long before winter did you change the compost? Did they have a chance to recover, heal and grow new roots?

I changed the soil in May (and none died at the time)

[Steve Johnson]

The word "soil" is sending up a red flag here, Shane. You might want to try going soil-less, and the 60/40 pumice-granite gravel mix I've been using successfully since 2012 should work well for you. Sunset Nursery in Silver Lake (not far away from where you live) sells the right grade of pumice. For the granite gravel, you can buy either crushed granite poultry grit on eBay or decomposed granite (DG) at Desert Creations in Northridge. If you go with the DG, you'll need to sift out the "play sand" fines and toss out the big chunks. Or you can use them as top dressing, which I did with a Pilosocereus azureus I got at Sunset Nursery in summer 2019:



A couple of things about the soil-less mix. First, you should thoroughly rinse the pumice and granite gravel before you start using it. Here's my "dirty" mineral mix on the left and clean mix on the right:



Second, you'll need to fertilize pretty much every time you water your cacti in the growing season. By the way, if you're watering with tap water, you can acidify it a little by adding 1 tsp. 5% white vinegar per gallon.

This gets us to why you're losing cacti even though you've been keeping them dry over the winter. Simply put -- their roots weren't healthy enough to grow as well as they should in the growing season. Let underdeveloped roots go dry in the winter, and you're likely to end up with dry root rot. This is a problem with soil-based mixes, and the open aeration of a soil-less mix gives your cacti the ability to develop a more robust root system. Robust means healthy, and that's how desert cacti can survive winter with little or no water.

[mikethecactusguy]

Shane , Steve, I know it goes against the grain but while I lived in LA I never really wintered my plants. I tried it for a few months but I could not bear looking at the plants shrinking up. It was hard since we went from 40 degree nights to 80 degree days. Weeks of cold temps but full sunny clear days.
So for me, I would water occasionally. I had 3 plants die on me due to rot. A Pilosocereus azureus was my worst casually. It died of cold damage. I had few other develop rot. One was because the drain holes were blocked. To protect those susceptible I would cover with heavy plastic bags during rains.
Just my journey.
Sorry you had so much loss this year Shane.
I miss Sunset Nursery and Desert Creations. You'd expect to find here in the desert something similar.

[Steve Johnson]

There's no "one size fits all" approach for wintering cacti, and here's what I found through trial and error (plus advice from more experienced growers)...

The roots of all desert cacti go through a certain amount of die-back when they're dormant in winter. The species that absolutely need occasional light watering (in other words, sip, don't soak) are the ones that'll have their roots die back to the point of no return without it. I'll give you a few examples from my collection, with the watering care I follow:

Discocactus buenekeri -- every 3 weeks
Echinocereus rigidissimus rubispinus -- once a month
E. viridiflorus canus -- once a month
Melocactus matanzanus -- every 3 weeks
Parodia subterranea -- once a month
Wigginsia vorwerkiana -- once a month

As you can see, that's a short list, although by no means exhaustive. In fact, it should be expanded to include all species of Discocactus and Melocactus. Not sure about juveniles, but when they start growing cephalia, Discos and Melos definitely need winter watering care. (By the way -- they won't survive temps below 39F, so not the best choice for growers who can't protect them from catching a deathly chill.) There may be other species that require occasional winter watering, so if less experienced growers are trying to grow species for the first time, they may want to ask more experienced folks about whether their plants need it or not.

For cacti that don't need any water at all during fall and winter, they can get awfully shriveled, but that's a natural aspect of dormancy. As I'm about to end my 10th winter with the collection, I'll tell you that every one of those shriveled plants will plump up nicely after they receive their first deep drink of the growing season. The key here is to follow the practices that encourage strong, healthy root growth in the spring and summer. If we're successful, it's fun to watch the cacti go from winter shriveling to spring plumping. Don't know about anyone else, but this is something I never get tired of seeing.

[keith]

The cause of death isn't clear.'

looks like rot at the roots which moved up the plant and killed it. I don't know what your cactus soil is ? looks like perlite and dark organic/peat. Maybe got too dry from too much organic which is hard to re-wet after going dry ? Organic can go bone dry it takes awhile but it does.

I also water my cactus in Winter if its been dry and windy like this one has AND no rain is forcast . larger cactus less water in Winter. I use regular sandy soil mixed with pumice and small gravel like 1/3, 1/3, 1/3 . I add more organic if its conophytums and dudleyas more sand if its lithops.

[Shane]

Thanks for all the responses. First, I want to clarify a few things. One is yes there is organic matter in the potting mix. I think about 40% though lower in some. I also want to clarify the types of plants. Most of the cacti are not difficult to grow and are the kind of thing you'd find at home deopt. Most of the deaths have been easy to grow species. That's part of what's so confusing

I think something that has also contributed is lack of sun. They've been in shade for months and are just now getting some sun. I think I took the cacti don't need sun or water when they're dormant too literally. We've all heard the stories of people wintering their cacti in basements in Eastern Europe in Soviet times, but those are just old stories. I'm sure there are more details there that I'm not aware of

looks like rot at the roots which moved up the plant and killed it. I don't know what your cactus soil is ? looks like perlite and dark organic/peat. Maybe got too dry from too much organic which is hard to re-wet after going dry ? Organic can go bone dry it takes awhile but it does.

I wondered about this. It certainly isn't the familiar rot which turns everything to liquid. My plants' tissue has remained pretty much intact, turned yellow and dried out. Perhaps it's some normally harmless fungus killing much weakened plants. I don't think soil wetness is playing any role. I dug up the last plant to die and it was bone dry down to the very bottom

Steve: I do intend to transition to a mineral only mix. I have for a while but I haven't gotten around to it. Mostly I want something that won't change over time (organics degrade of course). I'm not sure whether the soil was the cause here. The age of the soil the plants were in didn't seem to matter to which ones died

Shane , Steve, I know it goes against the grain but while I lived in LA I never really wintered my plants. I tried it for a few months but I could not bear looking at the plants shrinking up. It was hard since we went from 40 degree nights to 80 degree days. Weeks of cold temps but full sunny clear days.

I haven't really heard other people express this opinion, but I strongly suspect high temperatures affect dormancy nearly as much as low temperatures. I don't know that this is really relevant here, but wanted chime in with that

[keith]

I guess the roots die and the top part of the plant slowly dehydrates and then if left alone will succumb to fungus. if the roots don't die they let the fungus travel up the vascular bundles and rapidly infect the entire plant, that's quick mush usually orange.

Why this happened to your plants IDK. Airborne fungus from rotting leaves nearby or a big tree ? You leave them on the ground or are they on benches ?

[Shane]

Why this happened to your plants IDK. Airborne fungus from rotting leaves nearby or a big tree ? You leave them on the ground or are they on benches ?

They're on a cement patio

[Steve-0]

I keep quite a few of mine outdoors all winter and Mother Nature's rules apply 24/7. Yesterday, I picked a few up to get up close and personal with them and saw clusters of common red mites scuttling around when I lifted each pot. So I stepped in with chemical warfare. Normally, I avoid most chemical pest controls but sometimes I use it. Mechanical means or natural pest eaters is best.
I have loads of ants, earwigs and slugs which eat the fruit.

Point being, plants die even with the best intentions and care. I had one rainstorm do in a couple of mine last year and this spring found the Cactus Boring Beetle visitor had inserted eggs into a couple. One plant died and another half eaten one is in the wait and see mode.

If you want some replacements PM me and pay the shipping from two states away. I have 3-4 species I could send you.