Srasra wrote: ↑Mon Mar 18, 2024 11:05 pmThank you; sad but I expected as much. Is the other portion still salvageable? Showing no black spots. I plan on getting a new pot and the potting soil if you think I can split the two.
Nice thing about the forum is that experienced growers can help beginners go through the learning process, so you're coming to the right place. We do have a few important things to unpack here...
Your large columnar appears to be a San Pedro cactus (Trichocereus pachanoi), very common and easy to grow. Given the amount of plant material you have to work with, the necrosis isn't bad yet. Sterilize a sharp knife with alcohol and cut the stems above the necrotic tissue. If the exposed tissues are nice and green, give them a liberal dusting of sulfur powder. But if you see even a little bit of black stuff, continue to cut until you see nothing but healthy green tissue. Then apply the sulfur powder -- here's a before-and-after example of how to approach the process:
- Echinocereus_pectinatus_'Coahuila'02062015_06.JPG (95.14 KiB) Viewed 2356 times
Keep the cut stems upside down while the exposed tissues dry out and form a callus. 3 or 4 weeks should do it. In the meantime, shake off the excess sulfur powder once the tissues are reasonably dry. You can use that pot as a rooting pot, although you'll need to dump out the soil, then clean and sterilize the inside of the pot with alcohol or bleach (I think bleach will be better).
The stems will have to start growing a root system before your San Pedros are able to take up water, so don't even think about watering yet. When the cut surfaces are well-callused, here's the next step:
- Fill your rooting pot halfway up with a 50% Rosy Soil/50% mineral gravel mix. That's your substrate.
- Dig the stems most of the way (but not all the way) down into the sand. Stabilize them with a plant stake if required.
Mist the stems every 4 weeks or so -- believe it or not, this helps in the rooting process. Our Australian horticulturalist-in-residence (MikeInOz) has a
lot of experience with rooting cacti, and he gives his cuttings a year before he tips them out of his rooting box. Following his advice, you'll have to therefore be patient. Believe it or not, your San Pedros won't die of dehydration, so wait until you take them out of their rooting pot in spring 2025, clean out the sand, and repot with the 50% Rosy Soil/50% mineral gravel mix. At that point, you should be looking at nice healthy root systems, and the San Pedros will be ready to accept deep watering in spring and summer.
Don't know how many other cacti you have (I see 2 in your last photo), but you should be growing all of them with the 50% Rosy Soil/50% mineral gravel mix I'm recommending. Straight potting soil is fine for leafy nonxeric plants (African violets, ferns, etc.), not fine for xeric plants like cacti and succulents because it suffocates their roots. If you can't find pumice or calcined clay granules at your local nursery, Amazon gives you a nice selection to choose from:
https://www.amazon.com/s?k=pumice+for+p ... -doa-p_5_6
https://www.amazon.com/s?k=calcined+cla ... -doa-p_1_8
Speaking of...
Cacti need plenty of light, and growers who keep their cacti indoors as houseplants could seriously use better lighting. Not enough natural light in the house (the usual artificial lighting won't cut it either), so we can solve that problem with full-spectrum LED grow lights:
https://www.amazon.com/s?k=grow+lights+ ... -doa-p_1_5
Cacti also need good ventilation. Problem solved in the spring and summer because you can keep the windows open. For the fall and winter, it wouldn't be a bad idea if you place a fan near your cacti to keep the air moving.