Although the flowers of Nasturtium are attractive and colorful--I like the 'Dwarf Jewel' mix--my major reason for growing them is that I love to use the leaves and flowers in salads. The taste reminds me of watercress; others think Nasturtium tastes like radishes. Some even think it's too bitter to eat. It definitely has a spicy, peppery flavor. The name, Nasturtium, is of Latin origin and means "nose twister," no doubt referring to its pungent flavor.
Nasturtium leaves are especially good when the plant is young. As the plant gets older and the weather gets hotter--so does taste of the leaves and flowers. Since I am not a cook, I haven't expanded beyond salads and Nasturtium Vinaigrette, but there are numerous recipes using Nasturtiums that sound delicious. I wonder if I could convince my nieces, who are quite the chefs, to whip something up for me!