Owing to risks incident to all agricultural enterprises, the greatest conservatism must be observed in bringing on the books any enhanced values on account of the growth of trees, for the trees themselves may be destroyed at any time by pests, drouth, cold, or by some enemy yet undiscovered. The safe course, therefore, is to write such enhanced values on the books when they are realized by a sale of the property, observing the rule laid down elsewhere that Property account shall represent actual cost of land and improvements. Clearing new land and planting new trees are examples of improvements, but new trees planted in place of those which have died are renewals, not betterments.