Free will

[Ignorant]

You neglect the case wherein the fruit tree depends on something that is not itself contingent. 

I hope I have not neglected it, because god, as at least one non-contingent condition for fruit-making, would be a pretty embarrassing thing to forget! =)

I'm not sure I have neglected the principle:

"Even if everything in the universe happens without conditions (i.e. if the universe is necessary) save the 6 contingencies of a 6-sided die roll, then the universe necessarily causes exactly 6 contingencies. It isn't all or nothing." - Me

 In that case, it makes or doesn't make fruit necessarily.

The fact that there are two possibilities should make us suspicious of an equivocation of "necessarily" here.

In other words, if one of the fruit-making conditions is itself non-contingent, then fruit-making still depends on the non-contingent thing. Things which occur necessarily do not have a real alternative. If there is any condition at all for fruit-making, necessary or otherwise, then the fruit-making is still contingent upon that condition's obtaining.

In short, a non-contingent condition is still a condition, and an action depending on fulfilled conditions is still contingent. Now, can that non-contingent condition ever not-be-fulfilled? No.

Most important point: 

If the non-contingent condition were the only condition for fruit-making, and that condition were present, then the tree could not NOT make fruit, it is true. But the tree's fruit making is STILL contingent upon the non-contingent thing... so the fruit-making will absolutely happen, and it will absolutely happen CONTINGENTLY.

Here is my rewording of your own formula above :

You - "In that case, it makes or doesn't make fruit necessarily."

Me - "In this case, it doesn't NOT make, or doesn't make fruit contingently."