There are essentially two sentences in this structure. The first part, Heirloom tomatoes, grown from seeds saved from the previous year, only look less appetizing than their round and red supermarket cousins. The second part describes the look of Heirloom tomatoes and contains the meaning that although it looks less appetizing, it has better flavor. the semi-colon separates two complete sentences while a comma can't do the same thing. Choice D, although has to be followed by a verb and you don't c one there. therefore, E is the only possible choice