Climate is the most important consideration for choosing a plant for a rockery. Better Homes and Gardens recommends making rock gardens look like scenes from nature. The right flower choices distract the viewer from the utilitarian purpose of the rock garden, whether it's preventing an eroding slope, solving a hard-to-mow problem or covering up an awkward change in grade. Flowers, combined with interesting stones, concrete shards or earthenware containers, turn rock gardens into art forms.
Lavender is a versatile perennial that adds texture, pleasant scent, vertical design and movement to a rockery. It prefers dry soil and tolerates full sun. Lavender works well as a border plant or placed on higher ground where it will drain well. BHG reminds readers that lavender is also a useful plant that can be used in craft projects and cooking. Lavender is a member of the mint family, similar to rosemary, thyme and sage, and can be used either fresh or dried. The pleasant fragrance and colour will draw pollinators to a garden.
Use one of the many types of dianthus in a rock garden for a splash of colour. Dianthus is available in solid colours of pink, white, red, rose, yellow and also in bi-colours such as red/pink. The Garden Bureau lists dianthus as garden hardy for zones 4 through 10. Dianthus can be started from seeds but also is found at nurseries. Avoid buying leggy plants or any with yellowing leaves since this can be an indication of root rot. Be sure to pick off any dead blossoms to keep the plant fresh and blooming through spring and summer.
A good description of yarrow would include words like "hardy" and "versatile." Yarrow lends grace to rock gardens, and is also resistant to deer and rabbits, hardy for zones 3 to 10 and requires low amounts of water. Removing spent blossoms keeps plants blooming for months. Yarrow makes a nice looking flower for cutting and arrangement. It can be easily dried for winter arrangements. Yarrow blossoms are fragrant and attract butterflies.