My lemon (unknown type) has started to sprout the seeds while still in the fruit and on the tree. It's about 12 years old and was neglected by our tenants for nine of those years. Is this a cultivation, feeding, or a position problem?
Certified GKH Gardening Expert
This is referred to as vivipary or a viviparous mutant. It happens because Abscisic acid (which keeps the seeds from germinating) in the fruit either break down or are not produced in high enough quantities.
Lack of Abscisic acid can have a few causes. One would be unusual exposure to cold. Another is that the fruit produced or the plant itself has a mutation. It can also be caused by nutrient deficiencies, which would happen after neglect like you describe.
Since the tree has not done this before during its fruiting life, this is likely that this is a one time issue. Resume proper care and it will correct itself.