DatePicker not Available for telerik GridDateTimeColumn -

i created telerik:griddatetimecolumn using markup below. however, date in grid not editable. missing something?

<telerik:griddatetimecolumn                                           datafield="verificationdate"                                           headertext="verification date"                                          uniquename="verificationdate"                                           pickertype="datepicker"                                          dataformatstring="{0:m/d/yyyy}"                                          itemstyle-wrap="false"                                           itemstyle-width="200px"                                           headerstyle-width="200px" />