Mono bouquets in Boston: lilac, tulips and the city's own flower seasons
Harvard's Arnold Arboretum in Jamaica Plain grows more than four hundred lilacs in 173 forms, and lilac, a May flower, has its own section among mono bouquets in Boston. A city with that much lilac on its doorstep makes it easy to pick one variety by what is actually in bloom, and by the recipient.
Public Garden tulips and Arboretum lilac: one variety for a Boston spring
Spring arrives late here. Tulips in the Public Garden open from late April into early May, around the same weeks the Swan Boats, running since 1877, come back out onto the pond in mid-April.
Lilac follows close behind, flowering through May across the 281 acres of the Arnold Arboretum. This gives a short window where tulips and a lilac bouquet sit side by side as the obvious single-variety choice for the season, because their seasons overlap only briefly.
Hyacinth and narcissus open earlier still, the bulb flowers that start the northern spring before tulip and lilac catch up. A cut tulip keeps growing in the vase and leans towards the light within a day or two, so a taller vase than the stems first suggest is worth having ready.

Sunflowers, daisies or tulips when the recipient is a colleague
Office gift-giving calls for something that reads as friendly rather than romantic. Etiquette guides suggest sunflowers, daisies and tulips for exactly that reason: none of the three carries the weight a rose does.
A gift for a colleague is kept modest, and for a closer colleague it is best given quietly rather than announced to the room. A manager, by the usual etiquette, is not given gifts by staff at all: the custom runs from the top down, not the other way round. Where a department wants to mark something for a boss, it goes as one gift from the whole team rather than from any one person.
Sending to an office works best with the company name and floor number on the order, since a courier cannot always reach a desk directly. Where the building has a front desk and a pass system, the bouquet is left there and whoever accepted it is named back to the sender, a detail worth checking on delivery before placing a mono bouquet delivery in Boston for a workplace.

Massachusetts dahlias at their September peak, then the hardier varieties
Small Massachusetts farms cut dahlias from mid-July into early October, with the heaviest harvest in September. The category has the dahlia section; availability is shown on the product card.
For a bouquet meant to last, chrysanthemum, alstroemeria and carnation each hold for two to three weeks in water. A chrysanthemum's leaves tend to yellow before the flower itself fades, so stripping them off as they go keeps the rest looking fresher. In the US the flower reads as a cheerful one rather than a sombre one, which makes chrysanthemums an easy pick outside the spring and dahlia months. Once the weather turns, how a bouquet copes with a Boston winter is worth a look before ordering.
In spring, lilac or tulips follow the Public Garden and the Arboretum's own calendar; for a colleague, sunflowers keep things light; for a bouquet meant to outlast the week, chrysanthemums are the steadier bet. The delivery time for any of them shows on the bouquet's own product card, and a photo of the finished bouquet goes out before the courier leaves.