During these days,
many disciples of the Caotian Sect were breaking through, so every few days, people near the Heavenly Palace were undergoing Heavenly Tribulations. Such frequent Heavenly Tribulations likely meant that after a century, quite a lot of Thunderstruck Wood could be harvested, though it wasn't considered very valuable.
Thunderstruck Wood, this kind of treasure from heaven and earth, is classified by Grade and age. The so-called Grade refers to the higher the grade of Heavenly Thunder smashing into it, the higher the Grade of the Thunderstruck Wood, such as those Chen Qiu had undergone, like the "Annihilation Heavenly Tribulation" and the "Void Refining Ninety-Nine Heavenly Tribulations." Those struck by such levels of Heavenly Tribulations surely wouldn't be of low Grade.
However...
under such Heavenly Thunder, it was very unlikely that any trees could survive by chance.
Beyond that, they looked at the age, the older it was, the more valuable it became.
