No vegetable starts with qux. The leaf and the root of the ullucus are an edible vegetable.
As for q, there is quinoa, which is a grain, so I suppose that might be classed as a vegetable.
xigua
Jaffa Orange xylocarp - Hard Woody Fruit
A fruit that begins with s is a starfruit! I LOVE THEM!
· uvilla
· uvilla
zucchini
· youngberry
iceberg (lettuce)
· nectarine
PEA
Spinach
grapes