Cuttings often rot in water due to too much stem submerged, stagnant water, or damaged tissue. Rot usually starts at the cut end and can quickly spread if not addressed.
To save a cutting, trim back to clean, firm tissue, removing any brown or mushy parts. Only keep the node submerged, as this is the section that will produce roots. Change the water regularly to maintain oxygen levels and prevent bacterial buildup.
For added protection against rot and pathogens, you can add a small amount of hydrogen peroxide to the water (following safe dilution instructions). This helps sterilise the water and reduce microbial growth that can attack your cutting.
Monitoring cuttings closely and using clean containers helps reduce the risk of recurring rot. You can also plant weakened cuttings into a fresh perlite-based mix to help them recover and root successfully.