Forms :: Filling Listbox Within User Control

I created a user control with a listbox in it and a public property ListItem()
Public Property ListItem() As String
Get
Return _ListItem
End Get
Set(ByVal value As String)
_ListItem = value
End Set
End Property

On FormLoad I wish to fill the Usercontrol Listbox with the values that the user supplies.
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim u As New UserControl1()
u.ListItem = "hello"
u.ListBox1.Items.Add(u.ListItem)
End Sub
The Listbox does get filled.