How to handle your Dwarf Jade when it drops leaves.
Leaf-drop can occur on Portulacaria afra for a number of reasons. As discussed in your workshop, following a repotting in-class, your bonsai might want to use the sugars and other resources stored in their pads for redirection elsewhere while the new roots establish and fresh cuts callous over. [Link?]
Occasionally, this species will shed older pads as a natural cycle, and this can also be related to the growth of the tree and location for storing resources on branches and trunks. It is perfectly healthy. In the wild, these inefficient older pads will recycle into the soil. It is not suggested to leave any decomposing pads on the surface of your bonsai soil, if possible. These pads will attract pests and unwanted mold and fungi to your tree.[Link?]
During major seasonal change when the amount of sunlight for your bonsai will alter in strength can also prompt the shedding of pads. The reason for this drop is that P. afra are adapting the morphology of their pads for that difference in sunlight. For example, in Winter the tree might churn rounder pads while producing a flatter and wider pad for gathering as much solar energy as possible. This could be a time to consider supplemental lighting, and an article about light for your bonsai can be found [here], from Tim the Amazing, tamer of wild reptiles.
Sapsucking pests and certain molds or fungus can also weaken, corrupt, or drain, pads, causing them to fall off. Inspect your tree for insect pests or foreign substances that might be the source of the problem. [We have PowerPoints on both, or we can eventually do an article]
Most commonly, if the tree has been established in its new pot and surroundings for a while, or seems to be churning new growth before the pads have a chance to mature in the weeks following your workshop, the issue is related to hydration - and it could be either overwatering or underwatering. If you are unsure if you are watering too much or too little, refer [here]. Visually, the pads of a tree which is being underwatered, or struggling to take up enough water with the roots it has, or is otherwise losing too much moisture, will shrivel up and dry after being drained. If the pads of your bonsai are remaining mostly full, but are discolored and squishy when falling off, the tree is likely being overwatered. Please refer back to our article on watering for information about proper techniques and methods.
Leaf-drop of healthy pads might also happen from impacts, vibrations, or other physical stress like strong winds. Consider if the environment of your tree and the physical conditions if healthy pads are snapping off at the base.