Skyhold Herbs Garden

I have searched all over the BW forum, and on the web in general, but I haven't found anyone else with my problem.
I've upgraded Skyhold's garden to Herbs Garden but the pots, all six of them, remain inactive to me. I've collected seeds for every plant, so that shouldn't be a problem. Still, I can't plant - and consequently, harvest - anything in the garden, which means that the resources I've spent to upgrade it are lost.

Any suggestion?