My cactus is dying, please help

Trouble shoot problems you are having with your cactus.
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Steve Johnson
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Joined: Thu Nov 03, 2011 4:44 am
Location: Los Angeles, CA (Zone 10b)

Re: My cactus is dying, please help

Post by Steve Johnson »

Hello danieleatscookies,

It appears that you've been trying to grow your cactus in a potting soil loaded up with plant materials (chunks of tree bark, roots, etc.) -- way too rich for desert cacti, which is what you have. You'll need to lean it out with some sort of mineral gravel. Pumice is great, although I don't know if you can get it in Norway. Other good options are granite gravel and calcined clay cat litter. My default recommendation is a 50% soil/50% mineral gravel mix for free drainage and proper aeration of the roots.

Unfortunately your cactus looks like it's too far gone to recover, but if you can lean out your mix, you'll have a better chance for success when you get new cacti. Don't let this experience discourage you -- all of us had to start out as beginners, and learning the hard way comes with the territory. I just gave you lesson #1, so this will help you learn quickly. Here is lesson #2:
  • When you pot (or repot) cacti, size the pot to the roots, not the stem of the plant. Diameter -- there should be a 2 cm margin around the root ball or the base, whichever is widest. Depth -- measure root length from the base to the tip of the lowest root, then add a 2 cm margin below that. Aside from the problem caused by your potting soil, I think the pot was too big for your cactus.
Lesson #3:
  • When you pot (or repot), let the roots settle in for 2 weeks before you water the plant. This rule applies to potting/repotting cacti in the spring and summer. If you're trying to root cuttings, watering makes no sense until the roots grow in. However, what you can do is mist the stem once a month to keep it from shriveling too much. If I was trying to root a cutting now, I'd do nothing more than mist the stem until I stop watering the rest of my cacti in October (no misting for the stem), then unpot it to see if roots are growing next spring. The rooting process does take patience, so you may be better off by starting over with a new cactus that already has roots.
And lesson #4:
jerrytheplater wrote: Sat May 27, 2023 4:08 pmYou need more light if you want long term success. Without it, any new growth will be elongated and weak. No other windows? Otherwise get a very bright plant light.
Jerry is correct. Lighting technology has come a long way since "the olden days" when all we had were incandescent and fluorescent indoor lights. From Amazon US, this can give you some good ideas on what to look for:

https://www.amazon.com/FECiDA-Spectrum- ... RydWU&th=1

https://www.amazon.com/SUWITU-Spectrum- ... 425&sr=8-7

https://www.amazon.com/Grow-Light-Indoo ... 25&sr=8-15

IMO grow lights like the ones you saw are game-changers for hobbyists who'd like to grow cacti and succulents as houseplants indoors. Difficult to do in the past, not so difficult now.

By the way -- sorry to be picky about the terminology, but cacti have spines, not thorns. What's the difference? You'll find the answer in this little bonus lesson:

http://www.sbs.utexas.edu/mauseth/Resea ... Spines.htm
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
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