The main reason Asparagus Soup can become stringy is the asparagus are too thick or the tough, fibrous woody ends of the asparagus aren't removed all of the way. 2. Another possible reason for stringy Asparagus Soup is overcooking the asparagus or cooking it at too high of a temperature. Overcooking can cause the fibers in the asparagus to break down and become stringy. To avoid this, try cooking the asparagus for a shorter amount of time or at a lower temperature. 3. Finally, the stringiness could be due to the method of blending or pureeing the soup. If the soup is not blended thoroughly, the stringy fibers may not be broken down completely, resulting in a stringy texture. Try blending the soup in a high-powered blender to ensure that the soup is smooth and free of stringy bits. If you've already blended the soup and it's still stringy, you can strain it through a fine-mesh sieve to remove any remaining fibers.