Chaters Double Mixed Hollyhock Seeds 6515 Heirloom Flower. Tall plants 2 m (6′) high are loaded with fully double flowers in rose, salmon, buff, yellow, red or white with a cushion center. Hollyhock is a biennial that will not bloom until the second year, then they flower heavily, produce seed and die. For this reason we recommend planting seed two years in a row. After that, as hollyhocks reseed readily, they will soon become a permanent fixture in the garden. Plants do best in the garden when spaced at least 45 cm (30") apart.