1. Mexican sunflower
Tithonia rotundifolia By late summer, many of the flowers that have colored the garden all season begin to look tired. Include the late-blooming Mexican sunflower to shift the garden from summer through autumn in grand style. The bold plants, available in many nurseries and home and garden centers, grow almost 6 feet tall. Fiery orange, 2-inch blossoms appear like the blazing sun low in the sky, seeming to illuminate everything around them.
Wait to plant or sow seed until two weeks after the last spring frost date. Mexican sunflowers cannot tolerate the cold; leaves will yellow. They require a sunny place to grow and will not perform well where summers are rainy or cloudy.
2. Verbena bonariensis
From the day you started gardening, you were told to put the tallest plants in back. Break the rules with Verbena bonariensis. Although it grows to 6 feet, adventurous gardeners put it in the front of the bed, so they view the garden as if through a veil of slender, dark green, branching stems topped with 2-inch clusters of purple flowers.
Another late-season bloomer, it bewitches from midsummer to frost. You can think of it as a perennial because it readily self-sows. If you are a free-spirited gardener, you'll be charmed by its habit of self-seeding -- in the same place it had been growing plus a smattering of seedlings popping up in other parts of the garden. It can be fun to have one plant repeated in small numbers in different areas; it sets a rhythm to the garden.
Heliotropum arborescens Heliotrope is a wonderful old-fashioned flower that will perfume the nighttime garden with its vanilla scent. Its fragrance is reminiscent of long, lazy, Southern evenings, sitting on a swing on a wraparound porch, watching the sunset and fireflies, and slowly sipping an icy mint julep. The deep purple flowers (there are white and pink cultivars, but the purple is most fragrant) attract butterflies and moths. Growing only about 18 inches tall, heliotrope is perfect for the front of the garden and grows best in full sun and well-drained soil. Consider growing heliotrope in a container or window box where it will be closer to your nose. Get plants at local nurseries or home and garden centers.
Solenostemon scutellariodes If you remember coleus as the muted, multicolor pink, cream, and green leaves in your grandmother's garden, you are in for a shock. Breeders have created hundreds of new coleus varieties, including the Sun series, whose plants thrive in full sun, require little or no pinching, and add a tropical note to the garden. Although you can grow coleus from seed, the results are not predictable. When you find a coleus you particularly like, root cuttings in a glass of water to plant later in the garden. Coleus are not fussy and will grow in any well-drained soil. Keep them well watered until the plants are established.
5. Snow on the mountain
Eurphorbia marginata Like the closely related poinsettia, snow on the mountain has "flowers" that actually are specialized leaves or bracts. The true flower is inconspicuous at the center of the variegated green-and-white bracts. Growing to 4 feet tall, snow on the mountain is well-suited to the middle of the garden. Sow seeds after danger of frost has passed and where they will grow in full sun and well-drained, light soil. Give plants ample room, as they branch freely to 2 feet wide. Until about midsummer, snow on the mountain is fairly unremarkable. When the variegated bracts appear, the plant pops into view. It is especially handsome in an evening garden.