How Bad is Rot on This Euphorbia polygona?

[pone]

I am looking at a Euphorbia polygona that appears to have a fair amount of rot near the bottom of the plant. Based on the photo below, should I suspect that a lot of the root system has been rotted? What are the chances that this plant has unrecoverable damage and would only be usable for cuttings?

cactus_QDWpTiea_0CI0t2_1200x900_2.jpg (111.58 KiB) Viewed 3146 times

[esp_imaging]

It looks like a specimen plant in excellent condition to me.
The bases of older stems will good dry and woody, called corking. This is natural and not a symptom of poor health.

If they are soft and squishy, and seem to be filled with liquid, then you do have a rot problem.

[pone]

@esp_imaging in the bottom left corner, isn't that a hole going into the cactus?

[esp_imaging]

Maybe! Although looking carefully, I don't think so. Some of the older stems are quite narrow at the base. In any case, my previous answer still stands.
Leafy annual deciduous plants get to renew their leaves so they are fresh every year. Even evergreen plants renews their leaves every few years, so they can always look green and healthy.
Stem succulents don't have that option - the stems are exposed to the weather, UV, insect attacks etc for years on end. Inevitably the oldest, lowest parts of some stems will accumulate a little damage., or occasionally more than a little. It still looks very healthy, as far as I can see.

[pone]

If you took one of those stems with damage in the lower part and cut it all the way down until you find flesh, would it regrow a fresh stem there?

[Aiko]

I would not do this if I were you. I don't get the idea you know what you are doing. The white sap that will pour from this plant when you damage it is quite poisoinous. Don't get it in your eyes. This is not an cactus, but an Euphorbia. It comes from Africa, not the Americas.

Besides, the plant looks like it is fine (enough), I agree with esp_imaging. At least based on this picture. If you are worried the corking (or the hole) is not of your liking, which is perfectly normal for many succulents, you might not like the stub you leave behind if you cut stems off. Even then, I doubt the stem will root easily, if at all. It's not a cactus that can more easily reroot, after all.

If there is rot, you usually would know. The smell and the squishy tissue will let you know. If those two are not there, it is just a quite normal mechanical damage. No cutting with a knife will make that prettier.

[pone]

@Aiko I have a few large Firesticks, so I understand pretty well about Euphorbia sap. Is the sap of all Euphorbias as toxic as Firesticks' sap is?

I simply wanted to define what would be the growth response if I cut off the damaged parts of the plant.

Where should I be testing for rotting tissue on a large mature plant like this? Poke in all the outer stems at their bottoms?

[bartab]

Awesome plant. Where in the Bay Area?

[pone]

Awesome plant. Where in the Bay Area?

Near San Jose

[bartab]

I was wondering if you had to cover that at all on the colder nights. Looks like its been around a long time.

[pone]

@bartab It has been left outside during the Winter

[MikeInOz]

You can see the history of this plant. It went through a good year then a lean year then another good year then a not so good year and now it's growing well. I think it will do really well after it is repotted into a big bowl type pot and all the small shoots at the base will grow away and cover up the old corky bases.

[pone]

@MikeInOz What do you think about the idea of using pure pumice for the new soil mix? It is a Euphorbia, and I will be keeping it outdoors in zone 9a, which is always a potential risk. It is already living outside in zone 9a, so no major climate change. But I would like to put the plant in a position to survive some lower temperatures.

Pure pumice would drain winter rain rapidly and minimize the prospects of root rot. But being contrarian, pure pumice will also increase the porosity and air space in the soil, which during a freeze means that freezing air would easily access the roots. I do not have enough experience to know what soil mix will give the plant the best chance of getting through a tougher-than-normal Winter.

I am toying with replanting this into a quarter wine barrel, which will give it quite a lot of space to expand.

[esp_imaging]

This is many years old, so I'd try to keep conditions similar to what it's been used to. So repot in a soil mix similar to that already present. If you are worried about hardiness, considering temporary winter cover during freezes (wrapping in a cloth, for example), but it's a great plant, I wouldn't be keen on experimenting with worse growing conditions for it.

[pone]

@esp_imaging The plant is potted in clay soil, and the pot it is in is cracking open, so probably the roots are circling. There is no way I am planting a Euphorbia being left outside in the rain in clay. Maybe Polygona is not very delicate, but many Euphorbias would rot quickly in such conditions.