We have a friend who works for the USDA seed bank in Ames, preserving many varieties of seeds. One of the latest plants to be grown out for fresh seed was a variety of Hungarian parsley.
photo credit: ISU News Service.
This plant grew to be about 7 feet 10 inches tall. The whole story can be found on an ISU news page. The plant is in the process of being certified by the Guinness Book of World Records as it beat the old record by nearly 2 feet!
Now if you ever have to roast a whole cow and need a garnish, is the parsley for you to grow!
I once visited a place called Norfolk Island (out in the ocean between Australia, New Zealand and Tahiti)and found flat leafed parsley plants growing everywhere that were taller than me (6 foot 4)! They were not flowering and had leaves that were the same quality as you normally get in teh green grocer (yes I took a whole bunch of them and cooked with them).
Imagine the batch of Tabbouleh you could make!