The following may be simmered with the potatoes and leeks at the start: Sliced or diced turnips; peeled, seeded or chopped tomatoes or strained, canned tomatoes; half-cooked dried beans, peas, or lentils, including their cooking liquid.
The following may be simmered for 10 to 15 minutes with the soup after it has been pureed: Fresh or frozen diced cauliflower, cucumbers, broccoli, Lima beans, peas, string beans, okra or zucchini; shredded lettuce, spinach, sorrel, or cabbage; diced, cooked leftovers of any of the preceding vegetables; tomatoes, peeled, seeded, juiced and diced.