Toggle

<input id="dropdowntree" />

<script>
    $("#dropdowntree").kendoDropDownTree({
        dataSource: [{ text: "a-item1", value: 1 }, { text: "b-item2", value: 2 }]
    });
    var dropdowntree = $("#dropdowntree").data("kendoDropDownTree");
    dropdowntree.toggle()
</script>