The Frostbearing Tree is not far from the entrance to the Dragonspine mountain. In the marked location shown above, you will find a blue crystal inside a tree husk. You will need to destroy them by picking up the scarlet quartzes around the area, and hit the crystal with the effect still active. You have to do it one at a time, for about 4 times. The location of the scarlet quartzes are also marked in the picture above.
Levelling up the Frostbearing Tree
Crimson Agates are the collectibles in Dragonspine area, similar to an Anemoculus/Geoculus. You can find these scattered throughout Dragonspine.
Crimson Agate Locations
Credit goes to the facebook group. There are around 84 Crimson Agates in Dragonspine, but some players have said there are more than that, possibly from the treasure chests. Collecting all is enough to get to level 8, and get the rest from the Crimson Wish weekly missions.
There are a limited amount of Crimson Agates that can be found in Dragonspine, but once you reach level 8, you will unlock weekly quests, that are available every Monday and Friday, to obtain more Crimson Agates to reach max level.