Only five vegetables would be excruciatingly boring, it would be hard to get enough calories, and the more sources you have, the better the complete nutrition would be. At least go for ten, and fifteen would be better.

If you're dependent on a vegetarian diet (no meat/fish/dairy/eggs), your body still needs all the amino acid-rich proteins, so you would need to eat either grains+legumes, or nuts+seeds+legumes, or corn+legumes in the same day to get what you need.

Sweet potatoes
Regular potatoes
Beans
Lentils
Peas
Soybeans (complete protein, all amino acids)
Beet greens
Spinach
Kale
Broccoli
Tomatoes
Pumpkin/winter squash
Artichoke
Asparagus
Wheat
Quinoa (complete protein, all amino acids)

Sue