Thinking of you in Brussels: flowers that travel as an order, not a parcel
In 1910 American florists began relaying out-of-town orders by telegraph, so a bouquet was made by a florist local to the recipient rather than shipped across the map; flowers that say thinking of you in Brussels still work the same way. The order travels, not the parcel, so the real choice here is not the date but which flowers to send and what to put on the card.
Sending flowers to someone far away: how the order travels
JFLOO covers 113 cities in 59 countries, and the order form on the site takes about two minutes to fill in, any hour of the day or night. A local florist makes each bouquet to order, buying the flowers only after payment clears, so nothing waits in a cooler for a buyer who hasn't arrived yet.
Before the courier sets off, the sender gets a photo of the finished bouquet and can still ask for changes at that point. A second message follows once the flowers reach the recipient, confirming they arrived. How soon that happens isn't something this page can pin down. Most orders go out the same day they're placed, though the exact window shows on the bouquet's own page. The delivery page carries the current times for wherever the recipient lives.
Payment runs through Visa or Mastercard, priced in the local currency. A card issued elsewhere is simply converted by the cardholder's own bank at its own rate, and the service adds nothing on top of that.

Peonies dominate this list, from the Bunch of 35 Peonies and the "Pinky" Peony Bouquet to a Duo of Peony Roses and Peonies and the 21 Juliet Peony Roses. The flower has a real season: in the Netherlands, France, Germany and Britain it's cut from late April into June. Growers further south keep peonies in the catalogue for most of the rest of the year, though not for every month of it.
For someone who wants a bouquet still standing in two weeks, chrysanthemums and alstroemeria last that long in a vase, against roughly a week for a rose; that's why the 5 Pink Chrysanthemums and the 13 Mixed Alstroemeria sit on this list. Jumilia, loosely wrapped in the 51 Jumilia bouquet, holds for up to two weeks with proper care.
Lilies deserve a pause before you order them. Every part of the plant, the pollen and even the water in the vase, is toxic to cats, so the 15 Lilies and the 51 Lilies in a Basket are worth skipping if the recipient keeps one. A basket sidesteps the vase question entirely: its stems sit in wet foam that gets watered daily, over the whole surface, rather than in standing water.
The card, the surprise and what the courier says
The card is free with every order, and it can carry a signature or stay anonymous — that choice belongs to the sender alone. Nobody calls the recipient ahead of time unless the sender has asked for it; the one exception is a building the courier can't get into without ringing first, and then the call comes from the doorstep, not earlier.
The courier is handed only a name and an address, never the sender's own contact details, and delivers the bouquet in person along with the card, saying nothing beyond whatever the sender asked to be passed on. Where there's no address to give, a phone number for the recipient is enough to place the order.
Balloons, sweets, a small toy or a vase can go into the basket alongside the flowers, for anyone who wants to send more than one thing at once.
Sending thinking of you in Brussels starts with what's in season: peonies while the calendar allows it, a flower basket when there's no vase waiting at the other end, and the gifts to go with a bouquet page for anything beyond flowers alone.