Graduation in New York: chrysanthemums, roses and flowers for the dinner
At a graduation in New York a chrysanthemum usually reads as cheerful, as it does across the US, while in France, Italy or Poland a large chrysanthemum is kept for funerals. A family raised on that European custom may read the same flower differently, so the first question about a graduation bouquet is who it goes to.
Jumilia and lavender roses: the graduate's own bouquet
For the graduate herself, a bouquet built around 51 Jumilia in Airy Wrapping makes the point on its own. The bud opens white at the base and pink at the edge, so a large bunch of Jumilia reads as two colours before anyone gets close enough to see a single stem. With good care it holds in the vase for up to two weeks, well past the ceremony itself.
Most other roses last about a week, sometimes closer to ten days. 11 Lavender Spray Roses bring in that lavender tone, and spray roses, like other roses, last about a week in a vase. Where the shape is fuller and rounder, the peony-shaped rose behind it is usually an English variety bred by David Austin rather than a true peony. In the north-east of the US the peony flowers from late May into early June, which is when peonies are worth choosing instead.
Size is really a question of audience. A large armful reads as the main gift for the graduate; something smaller, handed from one classmate to another after the ceremony, does not need to compete with it.

In France, Belgium, Italy, Spain, Poland, Hungary and Croatia a large chrysanthemum is a funeral flower, kept for graves rather than gifts. In Japan it belongs to the imperial house, and in China it stands for long life, so a family with roots in any of those countries may read it differently.
In the vase, chrysanthemums and 15 Dianthus are among the longer-lasting choices here, holding for two to three weeks. The chrysanthemum's leaves usually turn yellow before the flower itself fades; strip them off as this happens.
Lilies are greenhouse flowers and sit in the catalogue all year, but their pollen is worth a thought next to a gown. Once a lily opens, the anthers can be pinched out with fingers or tweezers; if a stain has already landed on fabric, lifting it off with sticky tape works better than rubbing, which only pushes it in deeper. A lily bouquet is also worth skipping for a home with a cat, since the flower is toxic to them. For a family that keeps the Russian custom of odd and even stems, see how stems are counted.
Graduation flower delivery in New York to a restaurant or a flat
A dinner after the ceremony changes what the bouquet needs to do. For a restaurant table, the delivery time is arranged with the venue, so the flowers arrive at a chosen moment, dessert or the first toast.
For flowers going home after the dinner, a format that stands without a vase works better: a box, a basket or the Floral Handbag "Raphael". Anything arranged in floral foam needs water poured over the whole surface every day.
Orders for a set date and time slot are accepted for any delivery zone in New York. The bouquet is photographed before the courier sets off, and most orders reach the recipient the same day they are placed; the exact timing sits on the bouquet's own page. The delivery zones page lists the areas served, and a balloon or sweets to go with the bouquet can be added to the order.

Choosing where to start is mostly a question of who the bouquet is for and where it needs to end up: start with roses for the graduate, and flowers in boxes or flower baskets for a flowers-at-home evening, since both stand without a vase.