Light
Although common hollyhocks can tolerate partial shade, they prefer a warm, full sun position. Too much shade will result in these tall plants flopping over, but excessively hot, dry weather can cause lower leaves to wither and die.
Soil
Part of the appeal of common hollyhocks is their ability to succeed in most soils. They prefer fertile, heavy soils, but, providing you enrich poor soils with organic matter, your plants should still do well.
Water
Common hollyhocks prefer evenly moist conditions, but wet winter soils are problematic. If your soil is not draining well during a wet winter, you could amend it with compost to improve air circulation and drainage. Water the roots and not the leaves of this plant, as wet leaves promote problems with the fungal diseases these plants are susceptible to.
Temperature and Humidity
Hardy down to about 5 degrees Fahrenheit, hollyhocks are pretty cold tolerant. However, early frosts can damage the flowers. Ideal daytime temperatures for flowering plants are around 65 to 70 degrees Fahrenheit. Excessive humidity can result in problems with the fungal disease hollyhock rust.
Fertilizer
In terms of maintenance, one of the most important considerations for common hollyhocks is their nutrient levels. These plants love fertile conditions and are heavy feeders. Adding organic matter to your soil in the spring and applying an organic flower fertilizer or fish emulsion that is high in nitrogen every few weeks during the bloom period will result in bigger flowers and healthier foliage. Poor nutrient levels can result in yellowing of the plant’s leaves and disappointing blooms.
Propagating Common Hollyhock
You can propagate common hollyhocks through division in the fall or spring when the plants are not flowering. Take root cuttings in winter (around Decembe, and you can propagate basal cuttings at any time of the year. Make sure to select rust-free plants.
How to Grow Common Hollyhock From Seed
Common hollyhocks are easy to grow from seeds. Sow seeds around late spring or late summer. The ideal temperature for germination is around 60 degrees Fahrenheit. After danger of frost, direct sow in the garden bed about 1/4 inch deep and 18 to 20 inches apart. Cover lightly with soil. If you plan to start your seeds in pots, start about 2 weeks prior to the last frost. Select deep pots and transplant outdoors as soon as true leaves emerge. Hollyhocks have a deep taproot which, once established, may not transplant well. Regardless of where you start your hollyhock seeds, be patient: they typically take around two weeks to germinate.
Common Pests & Plant Diseases
The fungal disease rust can be a major problem for the foliage and it can quickly spread resulting in premature leaf drop and stunted growth. Removing the leaves on the lower part of the plant stem, cutting the plants back in the fall, and promptly removing the debris will help to minimize fungus problems and spread. You might also find that Japanese beetles and spider mites are attracted to your common hollyhock, and young growth tends to be a tasty treat for slugs.
How to Get Common Hollyhocks to Bloom
The flowers of the common hollyhock are large (around 4 to 5 inches in diameter), face outwards on the long central stem, and come in various colors, including white, pink, red, yellow, and lavender. Some say the flowers resemble those of opium poppies (Papaver somniferum). Although these plants are typically grown as biennials, meaning there will only be one flowering season, they have a long bloom period, lasting from mid-summer to early fall. A fertile soil with lots of nutrients, consistent moisture, and deadheading wilted blooms will encourage abundant, large, healthy blooms.
