My garden is a mixed border. I combine shrubs, trees, perennials, annuals and bulbs in a large curved bed. I designed it to be viewed from windows that run the length of our house. Because the garden borders the street I use tall perennials, including some with large foliage and flowers, to create a living screen that provides enclosure and privacy. Depending on the season, these same plants also add a sense of drama to the landscape.
Some of my favorite tall perennials are natives like Joe Pye weed, Eupatorium purpureum and the cup plant (Silphium perfoliatum). I got the Joe Pye weed from a friend who said it was "too tall" for his garden. In my garden I welcome the height it attains of 7 feet or taller. The whorled green foliage looks good for months and the clump is about 3 feet across. In late summer it produces large heads of purple flowers. Hardy from Zone 4 to 8, Joe Pye weed prefers full sun and regular moisture but mine does well in part shade and has tolerated periods of drought.
Growing next to this tough guy is the cup plant. This architectural curiosity has large leaves that are joined around the stem so that when it rains it catches water. Equally appealing to children and birds, it can grow up to 5 feet tall and in July and August rewards us with masses of yellow ray flowers. Hardy from Zone 3 to 7, this is a plant that benefits from neglect, full sun and poor soil. New York ironweed is a tall native that prefers moist soils and full sun. Numerous fluffy deep purple flowers appear atop 4 to 6 foot tall stems in late summer to fall. Hardy from Zone 5 to 8, this perennial also attracts butterflies.
Helianthus angustifolius, also known as the "swamp sunflower", is a great doer that may spread too quickly for some gardeners. Blooming in the fall with masses of bright yellow daisy-type flowers, swamp sunflower grows 5 to 7 feet tall. To keep it from spreading remove seedlings that appear as soon as you notice them.
Daylilies may not be the first plant that comes to mind when you think of adding height to your garden but 'Autumn Minaret' produces a clump of classic daylily foliage with a flower stalk that can shoot up to 6 feet in no time. The fragrant yellow-orange flowers are marked with a dark peach eye. With its see-through habit, this perennial is perfect for the middle of the border.
Combine these perennials with annual sunflowers or ornamental grasses like the Giant Eulalia Grass, Miscanthus x giganteus, which grows to a height of 10 to 12 feet. Perfect for a screen, accent or focal point, it also tolerates salt spray. Silvery plumes that appear in late summer add to its charm.
If you want to add some instant height to your garden, try carefree annuals like Castor Bean, Ricnus communis, which can quickly reach 6 to 15 feet. The large lobed leaves, 1 to 3 feet across, add interesting texture to the garden and cultivars like 'Sanguineus' offer blood-red foliage. Be warned the attractive seeds are poisonous.