Lovage
The fruit of the lovage plant can be used as a spice, but what appears in the trade as lovage seed is usually ajwain, not lovage. On the other hand, what is sold as 'celery seed' is often partially or entirely ground lovage seed.
As with many umbellifera such as parsley, celery, coriander, lovage leaves can be used in salads.
The root of lovage, which is a heavy, volatile oil, is used as a mild aquaretic. Lovage root contains furanocoumarins which can lead to photosensitivity.
Lovage is considered a "magic bullet" companion plant; much as borage helps protect almost all plants from pests, so lovage is thought to improve the health of almost all plants.
In Germany and Holland, one of the common names of Lovage is Maggikraut (German) or Maggiplant (Dutch) because the plant's taste is reminiscent of Maggi soup seasoning. In Romania the common name of Lovage is Leustean.
Celery salt is made with lovage seeds, not celery!