Are the fruits permitted to be eaten, and when?

To the questioner, 

Sorry for the delay in responding. 

There is no blessing over planting a tree. 

One must be concerned about the tree both because of orlah and because of sheviit. 

Any tree planted in the Land of Israel has its fruits forbidden for benefit during its first three years. 

Regarding the count of years, the halacha is that if a tree is uprooted and planted in another place, its three years are counted from its second planting; but if it was uprooted together with a clump of soil from which it can survive even if it were not replanted, it should be clarified with the nursery whether they sell the trees in a way in which the main roots are covered with clumps of soil from which the trees can live. If so, the first planting has not been nullified, and the original years are also counted for the years of orlah. 

Therefore, if you clarified that indeed the tree was uprooted and sold to you in a way that it could live from the clumps of soil around its roots, and if it is stated on the lemon tree (and they also told you at the time of purchase) that it already gave fruit in 2012, then you must count three years during which the fruits are forbidden for benefit from 2012 onward. The same applies to the orange tree if it also gave fruit already in 2012. 

However, there is a distinction between the time when lemons set fruit and their season, which is considered from the beginning of the month of May in one year until the month of May of the following year, and the setting of oranges and their season, which is considered from the middle of the month of September in one year until the end of the month of November of the following year.

~~~

If so, and if the years of orlah can already be counted from 2012, then this is what comes out, using the calculation for the lemon tree first:

If the lemon tree gave fruit already in 2012 - and this is considered from the beginning of the month of May of that year - then in May 2013 the second year began, and in May 2014 the third year began and ended in May 2015. It follows that until May 2015 all the fruits on the lemon tree were forbidden for benefit. 

Therefore, it is possible that the lemons you are describing now, which are on the tree, are already after the first three years and are permitted for benefit.

However, one must also take into account that these lemons began to set after May in 2015, which was the year 5775, a shemitta year; therefore, those lemons that are still on the tree have the status of shemitta fruits, and one must observe the sanctity of sheviit with them, even now, when the year has already changed and we are in 5776.

And practically, regarding the lemon that was placed in the fish, it is possible that it was permitted and that it has the sanctity of sheviit, meaning that one is obligated to eat it and not waste it; if so, it turns out, thank Hashem, that no mishap resulted from this. 

~~~

And regarding the calculation of the years for the orange tree:

If the orange tree already gave its fruit in 2012 (and it too was sold with clumps of soil covering its roots in a way that the first years when it bore fruit can also be counted, as above), since its season lasts until the end of November [as mentioned above], it follows that the fruits it has today are still within the first three years; therefore, one may not derive any benefit from them at all. And if it is not known at all when the orange tree first gave fruit, and you are also unable to clarify the matter, one should be strict from now on for another two years not to derive any benefit from its fruits at all, since in a case of doubt concerning observance of a Torah commandment, one must be strict. 

But from now on it would be good to determine exactly in which year the fruits are in their growth, and to conduct oneself according to the relevant halachot (for example, what is known that after the first three years and after the shemitta year, one must take terumot and maasrot from the fruits before they are permitted to be eaten [and with oranges, when they are in their fourth year, the law of neta revai applies]). 

With blessings, 

Rav Nachum