Thank you very much for your replies. I wrote to the Gardening Express and they assured me that it is normal to have plants looking like mine. But I do not agree that plants covered with lichen should be sold by Garden centres. At least they should warn their customers about such a possibility. I wouldn't have born any plants with lichen as, to my mind, the survival rate of such plants can be worse in general. I am greatly disappointed in Gardening Express and I doubt that I will be buying anything from them. I also bought roselily Tatijana bulbs from them and more than half of the bulbs are with rotten shoots.