According to Oregon State University Extension, "a plant can be deer resistant for several reasons. Many of the most deer-resistant plants are poisonous--some at all times, and others only at certain growth stages." To ensure a long-lasting garden landscape, plant deer-resistant flowering plants. Grown in a wide range of sizes, shapes and bloom colors, deer-resistant plants can reduce the costly damage that occurs when deer penetrate the landscape.
Yarrow 'Terracotta' (Achillea millefolium 'Terracotta') is a summer-blooming perennial flower that has as spreading growth habit and is suitable to grow in USDA zones 4 to 9. It grows up to 3 feet tall and has a spread of 1 to 3 feet wide. Yarrow has an aggressive growth rate and is tolerant of both deer and drought, creating a hardy flowering plant. The small, flat-topped daisy-like flowers (or corymbs) on terracotta yarrow range in color from salmon and peach to yellow and orange, and are accented by the silver and green textured foliage. Yarrow grows best in full sun and well-drained soil. Because of its vigorous growth rate, it requires that the plant be divided regularly to ensure it does not overwhelm the garden.
Arkansas Blue Star
Arkansas blue star (Arkansas blue star) is a perennial flower that grows best in USDA zones 6 to 8. It has a moderate growth rate and grows 1 to 3 feet tall and wide. The light blue, star-shaped flowers emerge in spring and attract butterflies to the garden. The clumps of feathery, pale green, willow-like foliage turns yellow in fall to create a striking presence to the garden and give the perennial its clumping growth habit. Arkansas blue star is an easy-to-maintain perennial flower that is also deer resistant and detracts these pesky animals from the garden. It grows best in full sun to part shade and well-drained, moist soil.
October Skies Aster
October skies aster (Aster oblongifolius 'October Skies') is a perennial flower that has a spreading growth habit and moderate growth rate. It grows up to 3 feet tall and wide and is an ideal flowering plant to grow within a flowerbed or border. October skies aster has a low-growing, mounding form and masses of deep sky blue, daisy-like flowers that emerge in fall to attract butterflies to the garden. The dark green, 3-inch, oval-shaped leaves on October skies aster are fragrant when crushed. Hardy, it is both deer and frost tolerant and will keep the fall garden in color throughout the season. October skies aster grows best in full sun to partial shade and well-drained, moist soil.