EF Core not delete related entity

I try to remove my entity with it related entity, but Entity Framework doen't want to do this.

Here is the code:

 var tr = _context.Trees .Include(x => x.Translation) .FirstOrDefault(x => x.Id == 2); _context.Remove(tr); _context.SaveChanges(); 

Context:

 modelBuilder.Entity<Tree>().ToTable("h_tree"); modelBuilder.Entity<Tree>().HasOne(x => x.Translation); 

Tree class:

public class Tree { public int Id { get; set; } public string Name { get; set; } public virtual Translation Translation { get; set; } } 

Anyone have idea why related entity can't be removed?

Translation class:

public class Translation { public long Id { get; set; } public string Pl { get; set; } public string En { get; set; } public string De { get; set; } public string Cz { get; set; } public string It { get; set; } public string Ru { get; set; } public string Fr { get; set; } public Translation() { } }