In a 6-quart stockpot, heat oil over medium flame with crushed red pepper for one minute. Add onion, carrots, and celery. Season with 1/2 teaspoon salt and 1/4 teaspoon pepper; cook five minutes or until vegetables are softening. Stir in fresh herbs and garlic; cook two minutes. Pour in wine and bring to a boil for a two minutes or so until wine is reduced.
Add fennel, leeks, 1" -2" asparagus pieces, vegetable stock, and water. Bring to a boil. Reduce heat and simmer until vegetables are tender -- about 15 minutes. Meanwhile, bring 1 cup of water to boil in a small sauce pan and add asparagus tips for 2 minutes. Drain and reserve.
Using an immersion blender (or in batches in the food processor or blender), blend the soup briefly and stir in asparagus tips. Taste and adjust seasonings. Ladle into warm bowls and garnish with a little freshly-chopped dill and a squeeze of lemon, if desired. Serve hot, at room temperature, or cold.