Normal shedding (not actually a problem)
Some older lower leaves gradually dry and are shed as a rosette grows. Other species detach healthy leaves easily when touched. Neither a plump fallen leaf nor its position alone proves normal ageing.
Check how many leaves are affected and whether the loss is continuing. Leave a stable plant alone while monitoring; investigate rapid or widespread loss. Only try propagating a healthy fallen leaf after confirming the species can reproduce that way.
Overwatering
Soft, translucent foliage and persistently wet mix warrant a drainage and tissue check. Cold injury can look similar, so review recent exposure too. Do not keep watering an already wet pot.
If the plant is collapsing, inspect the base and roots promptly. Remove clearly decayed tissue with clean tools where a viable plant remains. Use fresh, freely draining mix if repotting is needed; do not wait a guaranteed seven to ten days for rot to correct itself.
Underwatering
If the mix is dry, the pot light and the plant has been left too long without water, rewet thoroughly and drain. A dried older leaf will not become plump again. Check the remaining plant, and investigate roots if wilt continues despite moisture.
Shock
Record a recent move, heat or cold exposure. Shelter the plant from the harmful condition, while checking moisture and the base. Continuing loss should not be dismissed as adjustment. Photograph changes so you can distinguish old damage from new deterioration.
Keep a short care record
Photograph the whole plant and any damage, and note moisture checks and recent changes. Compare later growth rather than expecting an old scar to disappear. Continuing collapse, expanding lesions or extensive decay deserves specialist help.
Reference material
Reference material consulted for this independently written guide. The publishers listed have not reviewed or endorsed it.
- RHS — cacti and succulents
- University of Maryland — watering
- University of Maryland — symptom checks
- University of Maryland — root rots