Could not find the direct solution.
To implement this I used a hidden field and jquery.
On clicking the submit button, I smet the value of teh text area in the hidden field, then submit the form.
Here is the jquery code:
$('#add_product_button').click(function()
{
var description = $("#description").val();
$("#hidden_description").val(description);
$("add_product_form").submit();
});