[fix]

backend/project/api/events/models.py

@@ -1,6 +1,7 @@
 from django.db import models
 
 from api.core.models import BaseModel
+from api.tree.models import Tree
 
 
 class Event(BaseModel):
@@ -51,5 +52,11 @@ class Event(BaseModel):
         default="everyone",
     )
 
+    tree = models.ForeignKey(
+        Tree,
+        on_delete=models.CASCADE,
+        related_name="events",
+    )
+
     def __str__(self):
         return self.title