Jalepeno?
Jack fruit starts with a J.
Jerusalem artichoke and Jicama. (Jalepeno Peppers) if you want to count that.
The jitomate (Mexican Spanish for red tomato) qualifies as such. It however, is technically a fruit.
Iceberg lettuce is a vegetable. It starts with the letter i.
Fennel is a vegetable.
Onion is a vegetable. Oriental radish is a vegetable.
Beets are a red vegetable.
No vegetable begins with the letters ty.
'Celery' is a culinary vegetable that starts with a 'C' and ends with a 'Y'.
Green beans are a vegetable. Green cabbage also is a vegetable.
Vernonia Calvoana is a vegetable. It is a leaf vegetable.