It is often said that the roots of clivia rots. The commonest reasons will be the five listed below:
1.High temperature and waterlogging. Watering the plants chronically and heavy will made the roots soak in the waterlog and anoxic, thereby, the roots will rot.
2.An excess of, or too strong fertiliser will burn out the roots.
3.Using the old planting media all along for too long without replacement and never replace it will made the media airtight, thereby causing the roots to rot.
4.Watering superfluously after a long period of drought.
5.Using fresh leaves as planting media, such as the oak leaves which are not very decayed. These new fresh leaves will ferment in the pot and produce quantity of heat which may then burn out the roots.
You must take correspond measures as soon as you find the roots decayed. Here are several methods, wish them helpful to you.
1.Extirpate the rotten roots.
2.Clean the roots by a weak solution of potassium permanganate, this will disinfect and sterilise the roots. You can also daub the cuts with a similar solution or wood ash.
3.Replace the old planting medium. Control the amount of irrigation don't let it become too wet too soon, do not fertilise. The new roots will regrow after about 15 days.