Question

Cactus ID   QUESTION: Cactus is discoloring at base. turning a moldy black charcoal color. Plant is 6' tall. See photo. Top is in great shape... See pic.. Also what kind of plant is it?

ANSWER: The picture is a bit fuzzy but it does look like your plant has sever rot.  It is, I believe, a Euphorbia tetragona - a succulent, not a cactus.  Rot is caused by organisms getting into the vascular system of a plant that has been weakened by wounds, over watering, sustained cold, etc.  One often doesn't see the rot for many months or until it is too late.  Sorry to say, that is the case with your plant.  However, you can, with a sterilized knife, cut off the tops that are healthy, making sure there is no sign of rot where you cut.  The vasculature should be green and healthy, if it isn't cut above what doesn't look that way.

Let those pieces callous over for a week or two, moisten some perlite and or sand and just place the cutting on top and stake it in place.  It usually takes at least a month to root and until it does, just mist the cutting about twice a week.  Once rooted, you can pot it up.  Succulents need water all year (unlike cactus) but they don't need much.  This particular Euphorbia can go for long periods with out water.

Read up on this plant and succulents for more info.

Also, get rid of the dead plant and the soil - don't compost it.

Good luck.


---------- FOLLOW-UP ----------

QUESTION: We cut the upper good parts off and are letting them callous over. There was 4 shoots coming out of soil with the main one having the rot. After cutting good tops off I removed the main shoot out of pot. Now there is the 3 shoots left in the soil which seem like there is no rot on them. Could I leave them there?
Is present soil ok or should I put into new soil?
Is there a chance that I can separate them into different pots.

Thanks for advise.
Richie %26 Dee (Josh also thanks you aka plant)


Answer
Iit'a iffy but definitely worth a shot.  Definitely don't leave them in that soil.  Throw that soil away - don't compost it.  Sterilize the pot with the initial disease with Chlorox for future use.

If you can separate them with some roots on each you can put them in small separate pots.  Shake off as much of the original soil as possible.  I sometimes just run the roots under warm water.  You're trying to get rid of any of that diseased soil.  I would plant the min separate pots just to lessen cross contamination. Little shoots need small pots not much bigger than the width of the plant.  Plant is well drained soil of I part sphagnum (the kind that comes in the big blocks at places like home depot, 2 parts perlite or sifted builders sand that's been sifted so it's still gritty but the big rocks are out,  and one part good potting soil if you can find the kind that doesn't retain moisture.  If you don't need that much sphagnum (I use Canadian sphagnum) beg for enough  from friends, garden centers, etc. or just improvise. If you can find some fungicide powder to put in the soil that would be good or even small bits of charcoal help sweeten the soil and help drainage.  Some folks use coir which is pretty easy to find and crumble it up.  Moisten the mix enough so that it crumbles when you squeeze it.  I can't stress enough that the plants shouldn't be put in pots that are too large.  YOU may have to stake them till they can stand on their own.Put in filtered light initially, water when the soil feels dry and hopefully by the summer they will be established.

Let me know how you make out.  Write if you have any questions.