I have had problems with Euphorbia tirucalli "Firesticks" root rotting in containers, even when I use a dry succulent soil like @tapla Gritty Mix. Does anyone have a specific soil formula that has worked for them with this plant? I am thinking of modifying Gritty Mix to make the organic component only 20% of the mix.

50% pumice, 50% organic has worked for me. Pot needs to have hole(s) at the bottom. This plant should be relatively easy in a coastal California climate, provided it doesn't experience winter cold. Adjust watering interval instead of soil if you're already using a gritty mix.

Baja_Costero said: 50% pumice, 50% organic has worked for me. Pot needs to have hole(s) at the bottom. This plant should be relatively easy in a coastal California climate, provided it doesn't experience winter cold. Adjust watering interval instead of soil if you're already using a gritty mix.

I leave my pots outside in Winter, so they will get a LOT of rain some seasons.

What were the components in the 50% organic fraction you used?

I do of course provide for complete drainage in my containers and at this point have a lot of experience with container gardening.

Well if the meltdown is associated with winter rain, then go up on the amount of aggregate in the mix, increase the exposure (if possible) or find a spot under cover (if necessary), even if only for a few days a year.

The database has this plant as hardy to zone 10a.

Pencil Cactus (Euphorbia tirucalli 'Firesticks')

If that's accurate, you are just over the line and the coldest nights of the year may present a threat, especially when combined with rainfall (or recent rainfall). It might actually be the cold that is bringing your plants down, but cold and wet presents a greater danger. If that is relevant here, then you will want to seek out the warmer microclimates on the premises. Maybe right next to the house under the eaves on a south facing side? I have little experience with cold, just trying to think through the possibilities. I guess the timing of the loss would be informative about the reason it happened.

We have the same seasonal rainfall pattern as you (70% of our rainfall comes from Dec-Mar) but get about half as much total (about 10 inches in an average year, though the total may vary 3-4 fold from year to year). This is not a problem for this Euphorbia or most succulent Euphorbias that I've tried.

For the last 10 years or so my mix has consisted of 50% pumice, 25% cocofiber (coir), 25% generic bagged compost from my local nursery. Most mixes contain peat instead of coir. Ideally the compost should be something relatively gritty or chunky (not fine like powder). I would think composted bark would be the ideal product given its texture and durability. Avoid coir that is overly fine, as well.

Baja_Costero said: The database has this plant as hardy to zone 10a.

Pencil Cactus (Euphorbia tirucalli 'Firesticks')

If that's accurate, you are just over the line and the coldest nights of the year may present a threat, especially when combined with rainfall (or recent rainfall). It might actually be the cold that is bringing your plants down, but cold and wet presents a greater danger.

I think you are right about climate. The temperature here is probably just at the tolerable limit for the plant, so it becomes extremely susceptible to fungal infections during the cold season. This may or may not be something I can work around by lowering the percentage of organic content in the soil.

This is a less severe version of what I have experienced with Adeniums. I can get an Adenium to live outside in 40F temperatures as long as I never water it during the Winter. But a single watering during this hibernation period results in a massive root rot within two weeks.

I have tried to grow Firesticks in a pure mineral soil, typically pure pumice. It never did well in that.

My local nursery has a magnificent specimen planted in clay loam soil and it survives just fine in the exposed Winter conditions. They may have it at a slight elevation to help it drain, but there is no way clay loam is draining better than my Gritty Mix in a container. So there is a lot of mystery here and I don't understand this very well.

Yes, I hear you. But it sounds like you are gradually adding data points.

Plants in the landscape tolerate low temps better than plants in pots, generally speaking. I say this based on what I have read and not anything I have experienced. I think the ground is like a big heat sink, so it takes longer to reach low temps. Compared to a pot exposed to the cold air (and surrounded by it on almost all sides), anyway.

There are lots of other factors at play, too, like whether it warms up during the day. You can improve the warming up by providing max sun. Whatever promotes evaporation is good. You could move the plant under the eaves or under a table for the worst of the rain, when it is likely to be cold in the next week or so. Sort of stay ahead of the weather.

Or at some point just give up and move on to greener pastures, as it were. The winter rain is mostly a non-issue here in zone 11b (Adenium gets all of it) but the further one goes north along the Pacific coast, the shorter the list of succulents that can be left out in the rain.