Dear Thomas,
I am not an expert on plants to be quite honest but from the pictures taken on-board the Titanic and information I have I can might help you with it.
The first room which had plants in it which is documented is the starboard side Verandah and palm court taken in Southampton by reporters of “The Newspaper Illustrations LTD”. This is the only picture taken inside the Verandah and palm court (there is a picture of the chef cooks posing in front of the double doors of the port side Verandah café). Both rooms were fitted out in the Louis XVI style.
Both the starboard and port side had ivy and climbing plants on climbing up the green trelliswork panelling. In both rooms also palm trees could be found in a copper urn-shaped pot with an openwork design. These are most likely the potted plants you may wanted to see.
Moving down one deck we have the private promenades of the suites B-51 (in Adam style), B-53 (in Italian Renaissance) and B-55 (in Harland and Wolff bedroom A style/the French style) occupied by Mrs. Charlotte Wardle Cardeza and her son Thomas Drake Martinez Cardeza (it is believed that their maid Annie Moore Ward also would share her stateroom with Mrs. Cardeza while their manservant Louis Gustave Joseph Lesueur occupied B-101) and the suites B-52 (In Louis XVI style with oak panelling), B-54 (in Empire style with brass beds and with white and gilt panelling) and B-56 (also in Harland and Wolff bedroom A style) occupied by the chairman of the White Star Line Joseph Bruce Ismay. The 2 private promenades also had potted plants in them.
Even trough on the first picture the plants itself are not installed you can see the holders for the potted plants far aft. The picture was taken by Harland and Wolff her personal photographer Robert Welch during the fitting-out stage in March 1912.
The second picture of the starboard is taken on the 10th of April by photographers of the “Illustrations bureau”. The private promenade is now fully fitted out and has more plants. Since I am no expert on the subject I sadly am uncertain which plant this is.
The third and final picture taken by the Newspaper Illustrations LTD showcases the finished port side private promenade with the plants in the holders. Again I am not sure which plant it is.
Moving more aft we have the reception room of the á la carte restaurant at the after-Louis XIV staircase, this reception room was a new feature to the Olympic-class until the 1913 refit of the Olympic when it received her own reception room (located else were). The room was a combination of many styles, the panelling was in Georgian style, the staircase was in William and Mary style and the balustrades and bronze cherubs was in Louis XIV style. This room had 6 semi-circular plant holders for potted palms (2 of which are visible in the drawing). The drawning was used in the magazine “The Shipbuilder” and comes from the private collection of Joshua Inglis.
The next and last room on B-deck with plants (which can be seen in pictures taken on-board the Titanic) is the famous café Parisian, which had trained ivy and other plants climbing on the trellis-work panelling. The picture above was also taken by the “The Newspaper Illustrations LTD” in Southampton on the 10th of April
We are now moving down 2 decks to the D-deck dinning saloon taken on the 11th of April. This picture is taken by Francis Browne on the morning he departed from the ship. Even trough there are no potted plants visible in the room you can see vases with flowers on the tables.
As far I am aware these are all the pictures taken on-board the Titanic with plants in it. If you want me to analyse pictures from the Olympic too I would be glad to help you. I hope it helped.
Yours sincerely,
Thomas