Rabbits find many plants tasty and are especially fond of the bark of fruit trees, members of the rose family and anything in a vegetable garden. Some flowers exist that rabbits dislike, and it's worthwhile learning which these are for your garden's sake. As reported at HintsandThings.com, rabbits dislike plants with tough leaves, strong smells, milky sap and anything with prickles.
Globe Thistle (Echinops ritro) is not really a thistle, but its spiney leaves and blue flower heads will deter rabbits just as well. Globe Thistle looks attractive in the middle or back of flower beds, as will another blue flowered, thistle-like plant, Sea Holly (Eryngium alpinum). Crown of Thorns (Euphorbia milii) is an appealing pink-flowered plant packing a double whammy--with long thorns and latex sap, no rabbit will come near it.
Wormwood (Artemisia absinthium) fits nicely in this category as it is full of volatile and bitter-tasting oils. It also sports lovely tall spires with clusters of yellow tubular flowers above ferny, silver green foliage and makes an attractive background plant. Wild and ornamental onions (Allium spp.) are lavender colored globular flowers that look--and smell--attractive near the front of the border or in wildflower groupings but taste like onions. Rabbits despise them. Milkweed has milky sap that rabbits avoid, and it is an appropriate choice for butterfly gardens.
Yarrow (Achillea spp.) is an aromatic plant with flattened umbrels of white, yellow, orange, red or pink flowers. It is a long-blooming, medium-height plant, with finely cut foliage strongly distasteful to rabbits. Bee Balm or Bergamot (Monarda didyma), a native lavender-colored flower, also is available in red and pink cultivars. All are as attractive to hummingbirds and bees as their fragrant foliage is repulsive to rabbits. Catmint (Nepeta spp.) is another powerful-smelling but beautiful flowering plant. Your cat will love it, too.
One of the showier late summer flowers rabbits won't eat is the gold-petalled Black-eyed Susan (Rudbeckia hirta). It is drought-tolerant and has very tough, hairy stems and leaves. Many sunflowers (Heliopsis spp.) are similarly raspy leaved and resistant to rabbits, as is Blanket-flower (Gaillardia spp.)