Greenclaws (1989)

Greenclaws was a big green monster who lived in a greenhouse. The man who played Greenclaws was Nick Mercer. Every week, Iris would visit Greenclaws. They would put one of Greenclaws' fabulous seeds in a plant pot, put the plant pot inside a secret growing place in the Riddle Tree, wait for Owlma (a mechanical owl) to alert them that the plant was ready, answer three riddles/questions correctly from Owlma (which were always along the lines of "Twit twoo, twoo, twit twit twoo?" and then translated into English by Iris for her and Greenclaws to solve), then open the tree to find the plant had grown into something bearing unusual fruit