See the information at this Michigan State University Extension Web site. The hollyhock seed may be planted anytime after the danger of frost or freezing temperatures is past:
www.msue.msu.edu...
Alcea rosea — Hollyhock
Hardiness Zone: 3 to 8; Height: 6 ft; Spacing: 18 in; Type: herbaceous perennial; Flowers: Pink, white, red, purple, yellow. Hollyhock is a biennial but self seeds giving the appearance of a perennial. These short-lived plants produce flowers covering a wide range of colors. Alcea prefers a rich soil with lots of organic matter. Provide exposure to full sun as the plant dislikes any amount of shade. Because the coarse foliage is attacked by diseases, especially rust, plant hollyhock near the back of the garden. The diseased foliage will be hidden by shorter plants. Pinching one or two times early in the growing season gives shorter, plants with more branches. Dormant terminal buds are sometimes injured by freezing or over watering, so provide a mulch for winter protection. Double flowered types may need staking as they fall over after a rain because the flowers will hold a large amount of water.
Propagation: Hollyhock is usually propagated by planting new plants grown from seed. The plants may not live long enough to be divided. Division may be done in the spring but may be difficult due to a taproot. Each division needs to have an eye or bud. Seed can be planted any time between May and September. Young plants, grown from late season planting, need winter protection. The seed germinates in 2 to 3 weeks at 60 degrees.