If you want to make the best Asparagus Soup, you need to start with the best fresh asparagus you can find! Look for thin to medium asparagus that are firm and straight and not limp and saggy.  Avoid thick asparagus because they are often tough and woody and can make the soup stringy. Asparagus should also be bright green with a small amount of white towards the base. The tips should be compact and firm instead of loose and starting to spread or sprout.  When asparagus is going bad, the tips are the first indicator – they will turn a very dark green and will become mushy when touched.