Twin Pines

In ShadowClan territory, there are tons of pine trees, but not any like these. In a small clearing grow two pines, exactly the same in every way. Two kits, twins, were found abandoned under the pines. One pine will grow strong and one will wilt. How can the Clan tell which will be the wilted pine and which the strong one if they both look the same? Idea (c) Grasswing of Wingclan.