Characteristics

• Black hollyhock's 3- to 4-inch diameter single flowers are a deep chocolate-maroon that appears almost black. It grows from 6 to 8 feet tall with round, lobed leaves. Hollyhocks are hardy from U.S. Department of Agriculture Plant Hardiness Zones 3 to Zone 8.
  
  

Culture

• Black hollyhock prefers rich, organic, well-drained soil and should be kept on the dry side. This plant will not grow well in any amount of shade, so place it in full sun. Michigan State University advises pinching out the tops of branches once or twice early in the season for shorter, multibranched plants. Young plants that result from reseeding in late summer must be protected from the cold. Fertilize them with organic fertilizer or compost the first year and add bone meal the first winter to help young roots become established. During the second year, use a bloom fertilizer or a balanced liquid fertilizer such as 20-20-20 or 15-30-15.
  
  

Propagation

• Hollyhock is grown from seed planted in the winter, which blooms the following summer. Plants can be divided in the spring, but a long taproot can make division difficult. Each divison should contain an eye and a bud.
  
  

Problems and Considerations

• There are several diseases, pests and cultural problems that affect hollyhocks. Dormant terminal buds are sensitive to cold and must be mulched during winter to protect them from freezing. They are also prone to rot, and must not be planted where there is standing water after rains.
  
  Fungal diseases can also attack hollyhocks. Hollyhock rust is a problem that can be controlled with sanitation and fungicides. Cerco sporella leaf spot is identified by the angular gray-to-black spots, with older spots having tan centers with brown margins and can also be controlled with fungicides.
  
  Insect pests include hollyhock sawfly larvae; pale green worms with black heads that skeletonize leaves by feeding on the undersides. They are easily controlled with Sevin or Bacillus thuringiensis (BT) powder. Hollyhock weevil is a small weevil whose body is coverd by gray hairs that eats holes in seeds and flower buds. Control is by killing the adults before they can lay eggs, or by cutting and destroying stalks with infested seed pods.