Deer tend to avoid plants with a strong scent, even when that scent is pleasant to humans. Horsemint (Monarda citriodora) grows in partial shade and bears white to purple flowers in late spring and early summer, according to the Lady Bird Johnson Wildflower Center. The leaves of this plant have a strong lemony-mint scent.
Scented geraniums are actually not geraniums at all but Pelargonium species. These smaller plants are available in wide range of cultivars, each with an unusual scent. Scented geranium leaves smell like chocolate, mint, lemon, roses or ginger, just to name a few. These tender perennials are grown as annuals in most climates. Scented geraniums grow in partial shade and well-drained soil. Flowers bloom in the summer in a wide range of colors.
Although deer and humans don't share the same diet restrictions, many of the plants deer tend to avoid are poisonous to humans. Heliotrope (Heliotropium arborescens) is a tender perennial grown as an annual in all but the warmest climates. This plant grows to 18 inches tall and boasts clusters of purple, extremely fragrant flowers. The leaves are dark green and form a small bushy plant. This plant is seldom damages by deer according to Rutgers New Jersey Cooperative Extension. All parts of heliotrope are poisonous. Plant this flower in well-drained, moist soil.
Snapdragon (Antirrhinum majus) is another tender perennial grown as an annual with spires of unusual solid and bi-colored flowers. Depending on the cultivar, these plants grow 6- to 36-inches tall. All parts of this plant, including the seeds are poisonous if ingested.
Angel's Trumpet (Brugmansia sp. (Datura)) is another poisonous plant deer avoid, according to Rutgers. These plants bears large 5- to 7-inch flowers in the summer.
You might think that herbs would be one of the first victims of a roving deer, but due to their strong scent, deer leave many herbs alone. Whether culinary (a perennial) or annual ornamentals, deer avoid most types of Salvias or sages. Most need partial sun to flower.
Mexican Oregano (Poliomintha longiflora) is planted for its culinary uses, but this plant bears spires of fuzzy white flowers that attract butterflies and bees to the garden. This tender perennial herb grows as an annual in partial to light shade and, according to Central Texas Gardener, deer seldom damage it.
Many times, gardeners don't know why deer avoid certain plants, but they agree they consistently do.
Ageratum (Ageratum houstonianum varieties) grows to 30 inches tall and 18 inches wide. Fuzzy, purple flowers bloom from summer until the first frost, and attract butterflies to the garden. This plant prefers partial shade, especially in hot climates, and well-drained soil.