Looking for a plant named 'Mrs. J.D. Dewitt' you have to keep in mind that the database contains the official registration-names.
Lets say that the 'official' name is: 'Mrs J.D. de Witt' .
Entering the following will NOT give any results:
Mrs. J.D. de Witt (no . behind Mrs)
Mrs J D de Witt
Mrs J.D. deWitt
you will have more succes with:
(search is not case-sensitive)