Hollyhocks, (Alcea rosea) or Althea are biennial or short-lived perennial plants commonly grown for their numerous, ornamental flowers and relative ease of care. Hollyhock plants bloom during late summer and early fall, producing flowers on tall stalks in shades of red, yellow, pink, white or violet, depending on the variety. Native to temperate China, hollyhocks thrive in USDA Zones 3 through 9 and require only basic maintenance to successfully cultivate throughout the United States.
Site and Soil
Choose a planting site for hollyhocks that receives six to eight hours of full sunlight each day for optimal growth. While hollyhocks can be grown in partial shade, growth and flowering will be significantly reduced. Ensure that the chosen site contains well-drained, moist, fertile soil. Spread a 2-inch layer of organic, weed-free compost over the planting site and use a garden tiller to work the material into the soil to increase fertility and drainage to necessary levels. Space hollyhocks about 18 inches apart to allow enough room for mature growth.
Watering and Fertilizing
Water hollyhocks when the top 1 to 2 inches of soil is dry to the touch, about once per week, during spring, summer and fall. Reduce the watering frequency to once every two weeks during winter, when active growth has ceased and plants need less water. Do not overwater hollyhocks, as they are extremely susceptible to rotting.
Feed hollyhocks once per month during the active growing season using a low-nitrogen 5-10-10 NPK fertilizer. Soak the soil before and after fertilizing to release the nutrients and prevent root burn or injury. Apply at the rate recommended by the manufacturer's instructions for the best results. Do not fertilize during winter, when the plants are in a state of dormancy.
Deadheading and Mulching
Remove faded and dead hollyhock flowers, a process known as deadheading, whenever possible to improve the aesthetic appeal of the plant and prolong the blooming season. Pinch off the flowers close to the stem to minimize damage to the plant and reduce the risk of fungal disease. Allow some flowers to stay and turn to seedheads if you want the hollyhocks to self-propagate.
Apply a 2- to 3-inch layer of heavy mulch over the soil surrounding hollyhocks during fall, just before the first frost of the season. Begin the mulch at least 3 inches from the base of the plants to allow adequate air circulation and reduce the risk of disease. Replenish the mulch whenever necessary throughout the winter. Remove the mulch during spring, just after the final frost of winter to allow room for more active growth.