September is a month for the bright blooming summer annuals as well as the beginning of autumn's rich jewel-coloured flowers. Local climate conditions influence bloom times; the best resource for exact times is a local garden centre. Gardens in western and southern states are very warm in early September, while northern gardens begin to cool down considerably. September flowers in season include annuals and perennials, sun and shade plants.
The blue double larkspur is a dramatic tall spiked plant with ruffled, fully double deep blue flowers. Cosmos are a daisy-like flower with tubular petals that is available in mixed pinks and reds or shades of yellow to orange. Cosmos give masses of colourful blooms by midsummer, lasting into autumn. Zinnas and a wide variety of sunflower cultivars come to bloom by early September, bringing their strong yellow, orange and red colours to the garden. Petals on the Double Goldy and Supermane Sunflowers are finely ruffled with 5- to 7-inch blooms. Scaevola is a spreading plant that blooms summer into fall on trailing stems that are covered with hundreds of blue flowers.
Daylilies, tiger lilies and trumpet lilies are a good choice for early September bouquets or arrangements. They bloom in an array of colours and sizes, from pure white to spotted and bicolour yellows and oranges. Lavender comes to bloom in mid- to late summer and offers its pleasing scent as well as spiked blue and lavender flowers. Love-in-a-Mist Nigella is an annual that reseeds like a perennial, with delicate blue flowers on a fast-growing 18- to 20-inch plant.
Blue-eyed daisies thrive in full sun, giving a mass of colour by early September. Their white, pink, rose or purple flowers all have a blue centre. Hybrid mix calla lilies are another full-sun flower, now available in pink, blue, purple and variegated colour choices. The new hybrid calla lilies come in miniature and old-fashioned standard size blooms. Salvia Victoria is a classic mid-blue spiked flower that blooms prolifically on light grey-green foliage. Planted successively throughout spring and summer, it provides blooms through September until frost.
Rudbeckia Goldstrum thrives in sun and partial shade and blooms late summer into fall with bright yellow daisy-like flowers. It is a prolific bloomer. Hydrangea Masja also grows in both sun and shade, blossoming with bright pink-toned flowers from September to October. The Hungarian Blue Bread Seed Poppy grows in partial shade to bloom by early September. The bluish-purple flowers are followed by pods filled with culinary poppy seeds. Impatiens bloom in the shade from spring to early September and first frost. The Double Blondie hybrid has masses of yellow hooded flowers that have a delicate red and violet centre.