Penstemon plants, also called beard tongues, are herbaceous perennials that belong to the snapdragon family (Scrophulariaceae). Native to the United States, penstemon species are primarily winter hardy in USDA zones 5 to 8. Penstemon plants are associated with a few common leaf diseases.

1

Types

Penstemon plants are susceptible to several leaf diseases, including leaf spot (Cercospora) and rust (Puccinia). Powdery mildew (Erysiphe cichoracearum) is often a problem in wet, humid climates.

  • Penstemon plants, also called beard tongues, are herbaceous perennials that belong to the snapdragon family (Scrophulariaceae).
  • Penstemon plants are susceptible to several leaf diseases, including leaf spot (Cercospora) and rust (Puccinia).
2

Symptoms

Powdery mildew causes a white to light grey powdery substance to form on the leaves, while rust triggers the formation of rust-coloured horns or spores. Leaf spots typically cause small leaf lesions.

3

Control

Fungicides often help control leaf diseases. Infected penstemon plant parts should be pruned out and destroyed.

4

Other Problems

Penstemon plant leaves are also susceptible to foliar nematodes. These parasitic worms cause leaf drop, leaf lesions and leaf necrosis.

5

Culture

Penstemon plants thrive in dryer, well-drained soils in fully sunny locations. Wet or poorly drained soils favour leaf disease pathogens.

6

Fast Fact

Root rot and stem rot diseases also affect penstemon plants growing in wet conditions.

  • Fungicides often help control leaf diseases.
  • Root rot and stem rot diseases also affect penstemon plants growing in wet conditions.