Nedarim, Chapter Three, Mishnah Five
This mishnah deals with situations in which a person might attempt to take a vow to prevent either his saplings or his garment from being destroyed. In this case a person dedicates them to the Temple. Generally, when someone dedicates something to the Temple, if it can be sacrificed (such as a cow, sheep or grain) he may not redeem the item by giving money in its stead. However, if it cannot be sacrificed (a donkey, camel or bananas), then a person gives the worth of the item, and the item becomes non-sacred property.
1) [If one says,] Behold these saplings are a korban if they are not cut down; or, This garment is a korban if it is not burnt, they can be redeemed.
2) [If he says,] Behold these saplings are a korban until they are cut down; or, This garment is a korban until it is burnt, they cannot be redeemed.
Section one: If a person sees that something is about to happen to his saplings or to his garment, and he says that if the saplings are not cut down, or the garment is not burnt they should be a korban, they are dedicated to the Temple and they must be redeemed. We do not say that the vow was mistaken because he thought that the saplings would surely be cut down or that his garment would surely burn.
Section two: If he says that they are a korban until they are cut down he cannot redeem them, and if he does try to redeem them, they remain sanctified property. This is because he set a time for how long they are to remain a korban; until that time is up they cannot be taken out of that status. However, according to the Rambam, when the saplings are cut down, they are no longer a korban and he may use them as he wishes.