De Virtutibus

Accordingly, many husbandmen at the commencement of the spring watch their young trees, in order at once to destroy whatever fruit they show before it gets to any growth or comes to any size, from fear lest, if it be suffered to remain on, it may bring weakness to the parent tree. For it might happen, if some one did not take care beforehand, when the tree ought to bring fruit to perfection, that it will either bear none at all, or not be able to ripen any, being completely weakened by having been allowed to satiate itself with bearing before its proper time, just as old vine-stems when weighed down, are exhausted both in root and trunk.

But after three years, when the roots have got some depth and have taken a firmer hold of the soil, and when the trunk, being supported as it were on a firm unbending foundation, brows up with vigour, it is then in the fourth year able to bear fruit in perfection and in proper quantity:

and in the fourth year he permits the fruit to be gathered, not for the enjoyment and use of man, but that the whole crop may be dedicated to God as the first-fruits, partly as a thank-offering for mercies already received, and partly from hope of good crops for the future, and of a revenue to be derived from the tree hereafter.