Make sure you have a text field in your "blending_log" channel with the name "selected_tea" - otherwise SafeCracker won't save that value.
Your embed should look like this:
<select name="selected_tea">
<option value="" selected="selected">Select a Tea</option>
{exp:channel:entries channel="tea_herbs" order_by="title" sort="asc" dynamic="no" disable="member_data|pagination|categories"}
<option value="{url_title}">{title}</option>
{/exp:channel:entries}
</select>