UGLY BUT WORTHY. Bumpy, scabby, trailing hairy strands, the humble vegetable known as celeriac (celery root) is a zero in the looks department. But it is absolute genius in soup, or cut up and roasted. It tastes like celery, but richer and better. One uses celery, after all, mostly for crunch (as in tuna salad) or as a bland complement (celery sticks stuffed with peanut butter).
Leeks are praiseworthy, too. Although rather ungainly, with their long and useless sprouting green tails, they have a delicate oniony flavor that needs little embellishment. I like them sautéed in butter, maybe with a dusting of nutmeg and crème fraîche stirred in at the last minute.
Finally, parsnips. Unlike their slim orange carrot cousins, they tend to be stubby, pockmarked, and a nondescript shade of beige. However, they taste wonderful. I have made a parsnip-and-pear puree from The Silver Palate Good Times Cookbook that is sweetly delicious.
But nobody has yet managed to change my mind about beets (memories of steam-table school lunches) and okra (slimy!).