In a screw-top jar, combine white wine vinegar, olive oil, basil, marjoram, tarragon, capers, oregano, dill, mustard, pepper, and sugar. Cover and shake well.
Cook green beans in a small amount of boiling water for 6 minutes. Add carrot; return to boiling and cook 2 minutes. Add asparagus and peas; return to boiling and cook 2 to 3 minutes or until vegetables are crisp-tender. Drain well. Rinse with cold water.
Combine spinach, fennel, tomato, mushrooms, mustard greens or curly endive, summer squash, cucumber, and radishes in a large bowl or container. Add cooked vegetables and dressing. Toss well to coat all vegetables. For a picnic or potluck, cover and transport in an insulated cooler with ice packs.
To serve, garnish with edible flowers, if desired. Makes 6 to 8 side-dish servings.