Annuals tend to be the best choices because they have a broader range of flowering time and will re-flower easily after cutting. There are many choices available but my favourites would be tall Snapdragons, Sweet Peas, Zinnias, Asters, Calendula and Baby's Breath. They need a full southern exposure and a wall or trellis on which to climb. This year, I intend to build a trellis on the north side of the vegetable garden and train the sweet peas to grow up and form a colourful wall which will not shade the rest of the garden. The colour variations are extraordinary and the cut flowers are perfect for a small vase.
Gladiolus are easy and reliable flowers for cutting.
They are actually best suited as cut flowers because they can tend to get lost or look out of place in permanent display gardens. Gladiolus can be planted in early May and will produce their flowers 10 weeks later. By staggering the plantings every 2 weeks from early May until July, you will have a constant supply of Gladiolus from mid-July until October. A row of Gladiolus can divide the plantings of different vegetables for an attractive addition to the vegetable garden. There are many outstanding perennials, biennials and bulbs which can be used for cut flowers.