Cactus Blog 

Hi Cactus Jungle,

May I ask, do you know why this cactus body is become black spot?
I just bought my plant last week. Yesterday I clean the brown patch (dead scale) from the cactus body.. However, the spot that I clean become black spot.. Today I tried to clean that again and scratch & wipe it using alcohol. However the wound is turn to black again.. Is it normal? Is it a disease and can it spread to next plant? Do I need to repot the plant?

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Hello. Our Euphorbia has a top part that has grown quite large and the stalk will not be able to support it much longer. it is already leaning a lot (this photo is a few months old and it has gotten larger).

Is it possible to cut the top part off and plant it? How do these plants do with propagation and how do you suggest we do this. How will the bottom respond/heal from it? Is this a good time of year to do this?

I seem to recall there was a solution you suggested to put on this plant if we cut it as it releases some irritating sap.

Thanks!
Stephanie

You can cut below the branching top – leave at least 6 inches of stem below. You should wait until spring, winter is not a great time for this.

First be aware that this is a Euphorbia ammak which has a caustic milky-white latex sap. You need to wear gloves and long sleeves and eye protection when working around this plant. Given its height, this is going to take at least 2 people to safely take cuttings. One to hold the plant, one to do the cutting. If it is taller than it appears you may need a 3rd person to help hold the branch as it is being cut. Please make sure you feel safe with all this before you start. I recommend using a serrated bread knife to cut, and blankets to wrap the branch before cutting.

Basically you need to cut with enough left to be able to plant below the branching. Spray the cut with hydrogen peroxide and set aside to dry for 2 to 3 weeks. Spray the remainder as well, make sure to protect from direct sun until calloused over.

When the branches are fully healed over you can plant them in dry cactus soil and keep dry for a few more weeks. Water only every 3-4 weeks.

Stay safe, Peter

Dear team,
I would like to plant three Dasylirion Wheeleri in my garden. However, could you comment on their lifespan? can they live longer than 70 years?

Thank you,
Matt

Dasylirion are long lived, will grow a trunk and all, but I do not know if they live 70+ years – you can check with a botanic garden to see if they have any that are that old.

Peter

Hello,

I came across your web site and saw that you answer questions, so I thought I would try sending one. My friend gave me a large golden barrel pup from her father’s outside golden barrel cactus that lives in LA. I have been waiting for it to callus, and I went to check it today and the cut area was covered in a white fuzzy substance (pictures attached). I immediately thought of fungus, especially since it had been sitting in a box cut side down. I also thought it could be mealy bugs, and there was some orange color when I dabbed at it with alcohol on a paper towel, but not as much color as I would have expected if it was a dense mass of mealy bugs. I also looked at the cut surface and one of the pieces that came off with a 10x hand lens and I did not see any adults, just a dense matrix of white fluff. I had looked at it briefly when she brought it to me a week ago, and I do not recall seeing such a dense area of white fluff, although it was dark and I only looked very quickly. So whatever it is seems to have grown quite a bit in a week, although I can’t be 100% sure.

   

I attached some pictures, in the last one the spots where the cut surface is orange is where I dabbed it with the alcohol on the towel. It seemed to dissolve from the alcohol, it didn’t really seem to rub off onto the paper towel.

Do you think this is fungus, mealy bugs, or something else, and can it be saved? I was admonished not to kill the cactus so I would be very disappointed if I lost it even before planting it. If you don’t just answer random questions, I understand but thought I’d give it a try!

Thanks,
Rachel
California Department of Fish and Wildlife

It’s going to be a problem since it’s winter, to treat this successfully. It’s a fungus and likely bacterial. I recommend sulfur on the cut edge and treat the whole plant with a systemic fungicide like Infuse, after the sun goes down. Keep dry! Air circulation. It will be at least a month before you can try planting it, and a heat mat under the pot might help it root (warm and dry).

Peter