Hollyhocks (Alcea rosea) are old-fashioned plants that bloom in the late spring and early summer. The flowers come in a variety of colours, and each flower remains open for 3 to 4 days. Depending on the variety, hollyhocks can grow from 60 cm to 3 m (2 to 10 feet) in height. They grow as annuals, biennials or perennials.
Place the empty container in a sunny location. Make sure the container is in its permanent location, as it will be too heavy to move once filled. The container must have drainage holes at the bottom, so excess water can drain out.
Fill the container with potting soil.
Sprinkle hollyhock seeds over the top of the soil one to two weeks before the last frost date. Spring is the best time to plant hollyhocks.
Cover the seeds with potting soil to a depth of 6 mm (1/4 inch).
Water the soil in the planter with the sprinkle head of the sprayer. Do not spray hard, or you will push the seeds too far under the soil, and they won‘t grow. Keep the soil moist at all times. Do not saturate the soil. The first year, the hollyhocks will grow, but they may not flower until their second year.
Leave the hollyhocks to grow undisturbed, and they will self-seed next year. If you do not want hollyhocks to grow in the container again, remove each flower when the bloom fades. If the hollyhocks crowd each other, thin them out.
Fertilise the hollyhock plants two times during the season. Use an all-purpose fertiliser such as 15-30-15, following the directions on the label.
Hollyhocks do not grow well in containers because they have long roots and grow tall. The miniature variety of hollyhocks is better suited for container growing.