I have recently bought a lemon tree and did not notice until I got it home that it said the it was not for consum[tion. why is this
Are the Fruits of All Lemon Trees Edible
Certified GKH Gardening Expert
I would suspect that the lemon has been treated with a pesticide or another chemical that is not suitable to be eaten. The other possibility is that the fruit quality is so poor, that the fruit will not taste that good. Some citrus trees are meant to be grown for looks rather than as a food product.
As far as I know, there are no lemon trees that are dangerous/poisonous to eat the fruit from, so I believe it is the care or quality of the fruit that makes it not suitable for comsumption.