I have two informal maple bonsai (i.e., seedlings that I dug up from the garden and potted), both of which have some browning on their leaves:
Preliminary research indicates that this could be because of overwatering, underwatering, insects, fungi, or malnutrition (i.e., a lack of fertilizer). That's a wide field. Moreover, there's also a ficus that is doing just fine, with no browning at all.
- The fact that the ficus is OK suggests that it's parasitic, since they're all on the same watering regimen.
- There's adequate drainage and I check the soil before watering, so overwatering is unlikely to be the problem.
- However, the browning only appears on the older leaves, not the newer ones, so maybe it's part of the lifecycle of the leaves?
But all that is wild speculation. Can anyone help me narrow this down?