Hollyhocks are old-fashioned favorites we are used to seeing lined up against old houses and fences. Because they reseed so prolifically, they survive over decades and we think of them as solitary sentries. These tall, rambunctious plants are great companion plants, though. Use them in cottage gardens and vegetable patches to provide shade, height and color.
Hollyhocks are at home in full sun and resistant to drought. They grow from 4 to 12 feet tall, depending on variety. They bloom in papery open blossoms that open in succession along the stalks, beginning in summer. Perennial varieties may suffer from hollyhock "rust," a fungus treated best by early spraying and removal of affected foliage. They will suffer if subjected to wet conditions in winter, such as drainage from snow melt or early spring rains. Hollyhocks do not transplant very well and are best sown where they are to grow.
Hollyhocks are actually a group of plants, several of which are perennials---plants that live more than two years. The others are biennials---plants that take two years to flower. Some hollyhocks are also grown as annuals---their entire lifespan covers only one season. Hollyhocks and rose mallows are close relatives, both growing to heights that are best located in the back of the border. They bloom in shades of purple, red, pink, yellow and white; some blooms have a second color around the center. Leaves vary from flat, round leaves of rosea alcea to fig-leafed Alcea ficifolia. Modern hybrids include double-flowered varieties that are similar to cabbage roses and miniatures that stand only 3 to 4 feet tall.
Hollyhocks will happily grow alongside any plants that match their cultural requirements of full sun and very well-drained soil. Set yarrow, bellflowers and daisies in front of hollyhocks---they'll never compete because they like dry soil. Tall cactus zinnias, marigolds and sunflowers share hollyhock's love of sunshine. Like hollyhocks, none of these plants require heavy fertilization.
Rose mallow and phlox are fellow tall growers for cottage gardens that fill in gaps left by hollyhock's gangly growth habits. Foxglove and delphiniums also have blooms that balance the round, open shapes of hollyhock's blooms and rough leaves with long, tubular blooms and smooth, long foliage. Ornamental grasses like fountain grass provide contrasting forms. Deep purple or rosy hollyhocks also stand out nicely when lined along the fence of a citrus grove or apple orchard.
Hollyhocks should rule the roost. Their roots may steal moisture and nutrients from neighboring shrubs, so keep them away from the lilacs and delicately-rooted plants. Tulips, lilies along with other spring and summer bulbs that bloom before the hollyhocks will fit into a succession of bloom pattern nicely, though. Match their informal growth with floribunda and shrub roses. Peonies balance hollyhock's verticality with lush, shrubby foliage that can also mask the sometimes raggedy appearance of their lower stalks. Low-growing gypsophilia and blue mist lobelia fill lower elevations with delicate forms.
Although hollyhock rust and the hollyhock beetle do not generally affect other plants, it is necessary to provide space for access to these tall plants at the back of the border in order to perform cleanup when needed. Plan hollyhock placement carefully---they'll shade nearby areas.