Hollyhocks (Alcea rosea) are known for their stately height and vibrant blooms that appear throughout the summer. These towering plants are often biennial, forming foliage in the first year and flowering in the second before completing their life cycle. Proper maintenance once the flowers begin to fade is important for plant health and ensuring new generations of blooms.
Immediate Post-Bloom Pruning
Pruning decisions depend on whether you want a second flush of flowers or seed production. Deadheading, the removal of individual spent flowers before they form seed pods, extends the blooming period. This directs the plant’s energy toward producing more buds, sometimes resulting in smaller, later blooms until the first frost.
Once the main flowering season is over, the entire central stalk should be cut down. Trim the stalk back to just a few inches above the ground, or right above the basal rosette of leaves. This cleans up the garden and prevents indiscriminate self-seeding. Cutting back the stalk also eliminates a potential vector for overwintering pests and diseases.
Harvesting Seeds and Managing Self-Seeding
To maintain your hollyhock population, allow some flowers to remain on the stalk to set seed. Seed pods form at the base of each spent flower, initially appearing light green. Wait until these pods have completely dried out and turned brown or tan, which usually occurs in late summer to early fall.
Mature seed pods are ready for collection just before they naturally crack open and release their dark, coin-shaped seeds. To harvest, clip the dry pods from the stalk and allow them to dry further for a few days in a cool, dark place. The collected seeds can be stored in a paper envelope until you are ready to sow them in the fall or the following spring.
Alternatively, allow the plant to self-seed naturally by leaving the flower stalks standing. The seeds will drop to the ground and germinate in spring, often resulting in a dense stand of new plants. If you allow self-seeding, thin out the volunteer seedlings in the spring to ensure proper spacing and airflow for healthy growth.
Preparing Hollyhocks for Dormancy and Next Season
A thorough cleanup is necessary for the long-term health of the remaining basal foliage. Hollyhocks are susceptible to rust, a fungal disease appearing as orange or yellow pustules on the undersides of the leaves. All remaining foliage, especially any showing signs of rust, must be removed from the plant and the surrounding soil.
Discard infected debris in the trash rather than adding it to a compost pile, as fungal spores can survive and re-infect new plants. Removing the old stalks and diseased leaves reduces the opportunity for fungal spores to overwinter near the plant crown. Once the area is clean, apply a layer of organic mulch around the base of the plant for root insulation in colder climates. Refresh this protective layer in late fall, ensuring it does not directly cover the plant crown, which could trap moisture and cause rot.