Use extra stock to correct the consistency of the soup after blitzing.
Be careful when seasoning since some stocks can be quite salty.
The salsify is a rather unknown vegetable that was quite comment before the second world war but who feel out of grace after the war. Preparing the vegetable is a bit tricky. When peeled, a white sticky substance will be released and the white salsify will rapidly discolor, hence the lemony water. Wearing gloves when handling them is a sound precaution. The vegetable is typical for the winter time.