Keep cutting back the bottom end until you don't see any discoloration on the cut surface. Make sure you sterilize your knife between cuts. Once you get a completely uniform cut surface, you could apply fungicide or rooting hormone powder to the cut surface, but you don't need the rooting powder. Let the wound heal/callous over for at least a week before replanting. You will need to stake your plant to keep it from falling over.
I'm assuming the brown corky surface is the top. An old healed wound? You could cut that back also until you get a clean surface. Your plant will branch at that point.
Better idea would be to cut the entire piece up into pieces about 9" long, just remember which end is down on each. Let each piece callous over while holding the pieces upright in subdued light. You can plant them out after a few weeks and no staking will be needed.
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
Jerry, your description is very good. What I would like to add:
At the lower end I would bevel the ribs upwards away from the leading bundles. Then it will have an easier time growing roots.
At the top end I would slant the column pieces in total so that water runs off more easily outdoors. If water remains there standing, there is a danger of fungal attack again.
And please let me also emphasize: Time to get calluse is very important. Preferably let the plant (-pieces) rest a couple of days longer than shorter.
N.
Love and Revolution!
...and still more cacti.
Location: Stuttgart, Germany, getting definitely hotter every year.
I would agree with both. A nice clean callous is better than a discoloured (rotting) or a hard old one since those can often be hard enough to prevent the new roots penetrating easily. Therefore just trim the base back and leave it a week or so out of the sun for a clean callous to form before placing it on soil to root down.
