Florists' Transworld Delivery (FTD) was founded in 1910 under the name Florists' Telegraph Delivery. It took advantage of what was then the radical new technology of the telegraph, which enabled instant communication, to allow a group of florists to work together and form a regional network that could deliver flowers far more quickly than less technologically sophisticated rivals.
FTD adopted the "Mercury Man" as its logo in 1912. The logo shows Mercury, wearing his winged cap and sandals, holding a bouquet of flowers in one hand. The use of the Mercury Man was based on Mercury (the Latin version of the Greek Hermes) being a messenger god renowned for his speed of travel. Hermes also was the protector of travelers and the god of interpretation, communication, and translation (Hermes is related to the root of "hermeneutics"), and thus doubly appropriate for a firm that based its business model on using new communication technology. He was also the patron of merchants and the marketplace.
Acting as the messenger of the Gods, Hermes possesses a very unique role. He has the duty of delivering messages with speed and grace within the pantheon of the Gods and between the immortals and the mortals. His messenger capacity implies a quick grace to it, hence the winged sandals, and the general idea would be that once a message is commissioned to Hermes to deliver, it would be brought forth quickly and without deviation. This might underscore why the floral delivery service, FTD, has appropriated Hermes as their symbol. Flowers have to be delivered quickly for they might perish if there is delay. At the same time, there are usually messages attached to the delivery of flowers that have to be delivered with all possible dispatch. This would be where Hermes might be a good symbol for a flower delivery service, like FTD.