Valentine cards of the nineteenth century very often incorporated flowers, either as the main image, decoration or both. The choice of flower was by no means accidental: each bloom had a meaning, understood (but how well?) by both sender and recipient. Although red roses are the universal symbol of love even now, pansies are still associated with thoughts and lilies with purity, the meaning associated with most other flowers has been lost over time.
Decoding the language of flowers is not easy. Apart from inevitable variants according to the sources used, a fairly thorough botanical knowledge is called for. Kate Greenaway (in 1884) has 33 entries for rose, all with different meanings: The language of flowers, 
A yellow tulip signified hopeless love or cheerful thoughts, but a red one a declaration of love, while variegated tulips conveyed beautiful eyes.
Then, there are the mixed bouquets! Combinations of flowers pose particular problems to the 21st century viewer.
Since most valentines were composed of different elements, the intention could be clarified by the scrap bearing the text, itself sometimes incorporating a flower.
This year’s joint project with the National Valentine Association (USA) has led us to digitise scores of valentines from the John Johnson Collection, which can be seen online for the first time and to share via Pinterest images from other collections, institutional and private, British and American: https://uk.pinterest.com/johnjohnsoncoll/
We have also included Mullord Bros’ card game: The language of flowers, which gives a guide to flowers’ meanings in the late 19th century, taken from ‘the best authorities’.
If you can add to our knowledge of the power of the flower to impart meaning, or if you would like to share valentines from your own collection with us on our Pinterest site, please email firstname.lastname@example.org
Like to know more?
Hundreds of dictionaries of ‘floriography’ were published in Victorian Britain. Some 19th century British and American sources easily consulted online include:
The language of flowers: an alphabet of floral emblems London, New York, 1857: https://archive.org/details/languageofflower00lond
Adams, Henry Gardiner The language and poetry of flowers New York, Derby & Jackson, 1853: https://archive.org/details/languagepoetryof00adamiala
Ingram, John Henry. Flora symbolica; or, The language and sentiment of flowers. Including floral poetry, original and selected. London, F. Warne & Co, 1869: https://archive.org/details/florasymbolicaor00ingr
The language and poetry of flowers, and poetic handbook of wedding anniversary pieces, album verses, and valentines, New York, Hurst & Company, 1878: https://archive.org/details/cu31924067884076