i had two cacti that the bottom of them rotted away i'd like to know if i can still save them or just disgard them and also what i did wrong if anyone could help i would appreciate it thanks
Rot is the result of too much water. You need to let the soil dry out completely before watering again. In the winter you water even less then that. You could try to cut off all of the rot and replant them as cuttings. Be sure to let the cut end dry and scab over for a week or so be for planting it.
The first photo shows a myrtillocactus geometrizans that does indeed look like there is a root-rot or root problem. The lower part of the cactus is discoloured and seems to be suffering from either drought or rot. It may be both because if the roots rot, the plant can't get any water. Check to see if the lower part is squishy. If it is relatively firm it might not be in such bad shape. If it is squishy, you will have to operate. Cut the top of the plant off at about 2-3 inches above the rot. The cut area should be GREEN and firm (not oozing or bruised looking). Coat the cut area with a powdered root stimulating hormone preferably that contains an antifungal. Leave the cut to dry for 2 - 3 weeks. I might put it upright in a container of perlite or dry sand a few days after the cut has dried, but NO WATER. After 2 - 3 weeks it should be safe to put it into a cactus potting mix. The soil can be humid but not damp. Leave the plant half buried in the soil for a 3 weeks - 1 month. After a month, if the cactus has not rotted further, you might look to see if roots have formed. Be gentle and do not break any roots because you might not get a second chance. If you are using a flower/plant pot, check the bottom holes first to see if roots are visible. If they are then you don't have to unearth it. If there are no roots visible or if you have no holes, then gently pour out the soil and plant trying not to break any roots that may have formed. Once roots have formed you can slowly start watering. I sometimes try to keep the soil a bit humid (not damp!) when I try to root my cuttings. Too much and you'll get rot and you'll have to cut off the affected tissue (again) and the cactus gets smaller and less likely to survive. In any case, the plant in photo 1 is easy to find and not expensive. If it does die it should be easy to replace. Good luck Waz
