To have your garden make a big impact even from a distance, plant tall, yellow perennial flowers. Yellow flowers show up well from a distance and taller ones stand out even more in the landscape. Or you can create a living fence with one or more types of yellow perennial flowers. Planted at the back of a perennial border, yellow flowers create a calming backdrop for the riotous colors of summer-flowering perennials.
Sunflowers are well-known as an annual flower, but a perennial variety (Helianthus multiflorus) exists as well. It grows to a height of 7 to 12 feet and spreads up to 4 feet wide. Perennial sunflowers bloom from late June through September on branching plants that produce chrysanthemum-like flowers that are 3 to 4 inches across, much smaller than the annual varieties. They are hardy in USDA hardiness zones 4 through 10.
Available in a wide range of colors, yarrow (Achillea filipendulina) grows 4 feet high, blooming in June and July. Yarrow prefers dry soil and full sun and withstands drought well. Protect yarrow from high winds, which can blow over the tall flower stems. The flowers of yarrow are up to 4 inches across. Yarrow easily self-seeds in the garden. It is hardy in USDA hardiness zones 3 through 8.
Widely grown for the florist industry, dahlias (Dahlia spp.) come in every color except blue. The variety "Shining Star" produces large yellow flowers on plants that grow up to 3 ½ feet high. Dahlias are tender perennials that grow from rhizomes which must be dug up and stored over winter or they will not survive. Plant them from mid-May through mid-June; don't plant them too early because they need to bloom at the end of summer when the weather is cooling off. Fertilize dahlias sparingly and do not use high nitrogen fertilizer, which will cause them to only grow stems and leaves at the expense of flowers.