Hollyhock is a biennial flowering plant that self-seeds and thus can appear to be a perennial. Hollyhock does best in a well-draining soil that is rich in organic matter. Hollyhock flowers can include yellow, pink, white, red and purple blossoms. Plant hollyhock near the back of your garden to hide any problems lower on the plants. Hollyhock is susceptible to some common pests, some of which are treatable via companion planting. Hollyhock can grow to between four and six feet tall.
The two most common hollyhock pests are Japanese beetles and hollyhock weevils. They can also be susceptible to fungal problems like rust. Rust tends to affect the lower areas of the hollyhock and does not have a companion plant that will reduce rust. Because of potential rust problems, planting the hollyhock at the back of your garden is a good idea. Hollyhock weevils also do not have a companion plant that will deter the insects. However, a number of companion plants will deter Japanese beetles, a common hollyhock pest.
Geraniums can be a beautiful companion plant for hollyhock. Geraniums grow to between one and two feet tall, making it a good front plant or mid-bed plant in front of hollyhock. Geraniums flower with 1-1/2 inch wide pink, purple or magenta flowers. In addition to their attractiveness when paired with hollyhocks, geraniums deter Japanese beetles, a common hollyhock pest.
Meadow rue can grow very tall. Its height can range from between three feet and eight feet tall. Because of its height, it is often best planted interspersed with hollyhock. Rue flowers come in a range of colors, depending on the variety. Meadow rue deters a common hollyhock pest, the Japanese beetle.
Tansy is a shorter flower that grows to a maximum height of between one and two feet. Tansies produce a visually interesting multi-part flower cluster that contains many purple flowers with fine hair-like structures. In addition to looking nice with hollyhock, this flower also deters Japanese beetles. Because of its short height, it is best planted at the front of your flowerbeds with the hollyhock planted toward the back.
Although it does not have a direct beneficial effect on pests, baby's breath can be an attractive companion plant for hollyhock. Baby's breath grows to around three feet tall, so it can do well interspersed with hollyhock or planted between the taller hollyhock and shorter flowers at the front of your flowerbeds.